Good Growing Practices - an Overview for Beginners

Good Growing Practices - an Overview for Beginners


My hope is that this thread becomes a gathering place for beginners and the experienced alike, a place where reliable information that is rooted in sound science and horticulture can be found. We’ll see how that ‘gathering’ part goes, but I have enjoyed enthusiastic participation on many of my other threads, so I am optimistic.

As I consider what I am going to share with you and how to go about sharing it, I am compelled to offer some background that will hopefully allow you some degree of comfort in placing some measure of value on my commentary. I enjoy the growing experience tremendously. I have worked hard toward increasing my skill level for more than 20 years, and I look at sharing what I have learned about the growing sciences as a natural extension of the enjoyment I get from nurturing plants - sort of nurturing people who nurture plants. I am invited to lecture frequently in the mid-MI area, and occasionally beyond. I lecture, conduct workshops, and do demonstrations on a variety of subjects related to growing, but most frequently I talk about things related to container culture, with maintaining houseplants being one of the most requested topics. I also enjoy participating here on Dave’s and at another popular garden forum. Hopefully we will be using some links to some of my other offerings here that will help you share some of the confidence others have in the reliability of my offerings. Those that know me know I am not after recognition or glory, I simply feel I can help any beginner with a willingness to learn and apply the newfound information, as have so many others, and I get a large measure of personal satisfaction from the feeling I may have helped someone along the path to becoming a better grower.

The first challenge is to offer information that a beginner can digest, and in such a way that he or she feels it is important enough to act on. I am first going to flesh out the main issues that, if understood, will make anyone a better grower and hope I’ve created enough interest that there will be plenty of questions so I can go into greater detail in the answers. For what it is worth, I tend to look at growing anything in containers from the perspective of what is best for the plant, not what is best for the grower. Far more often than not, the two ideas are mutually exclusive, so if grower convenience is a large priority of anyone reading this, there is not much sense in reading on. Growing well does take a little thought and a little effort.

The houseplants we grow are perennials nearly all, capable of growing for many, many years and of being passed from generation to generation. With attention to the areas I’ll cover in this post, you will discover you can maintain your plants in good health for as long as you continue to commit to providing favorable cultural conditions. Your plants are all genetically programmed to grow well and look beautiful. It is only our lack of knowledge and skill in the area of providing the cultural conditions they prefer that prevents them from growing to their potential. That sounds harsh, but it’s the truth.

I have never seen anyone other than me discuss growing plants in containers from this perspective, that is (and it bears repeating) your plants are already genetically programmed to grow well and look beautiful, but it’s up to you as a grower to eliminate the limitations so often associated with growing in containers. This post is about isolating some of the factors that are commonly the most limiting and helping you to reduce the limiting effects. For more information on the concept of limiting effects, do a search using the words “Liebig’s Law of the Minimum“

Soil choice - Growers should realize that the most important choice they will make when establishing a new planting or when repotting is their choice of soil. A poor soil is probably behind more than 90% of the issues that growers come to the forums seeking remedial help for. Collapsed or dead plants, spoiled foliage, insect infestations, disease issues are all symptoms usually traceable directly or indirectly to a poor soil. This is so important to understand, that I will devote the bulk of my effort toward making it clear why I offer this contention.

Light is extremely important to plants. Plants make their own food, using water, CO2, and energy from the sun. Inadequate light means the plant cannot make enough food to grow to the potential it was genetically programmed for. I will not go into great detail about light because when it comes to houseplants, you either have good light or are forced to deal with the limiting effects of inadequate light. If the thread takes off, we can discuss supplementing light and how to prune to help compensate for the leggy appearance caused by insufficient light, or other topics of interest relating to light.

Nutrition supplementation is a requirement for normal growth and good health when growing plants in containers. In the earth, many of the nutrients are supplied by minerals in the soil. Container soils usually have no mineral component (and it is best that they don’t in most cases - more later), and the sol components break down so slowly and are washed from the soil so quickly that deficiencies are virtually assured if you do not fertilize.

Repotting vs. potting up - that there is a difference is a concept foreign to most hobby growers. One practice ensures your plants will at least have the opportunity to grow to their genetic potential within the limits of other cultural conditions; that would be repotting, with it’s accompanying root maintenance, complete or partial bare-rooting, and a change of soil. Potting up, on the other hand, only temporarily allows the plant to grow a little closer to its genetic potential before root congestion and a lack of fine roots quickly returns the plant to the state of limited growth and vitality it was experiencing before potting up.

Watering habits - extremely important and inextricably linked to soil choice, which is why I saved it until the end - so it would lead me back to the most important consideration - the one most apt to determine the difference between frustration and a rewarding growing experience.

Air is as important as water in soils. Plants absolutely love plenty of air, and rebel very quickly at too much water in the soil. I’m going to describe what happens when you water plants growing in a soil that retains too much water. There are actually two possibilities. The first is, you water, and a part of the soil near the bottom of the container does not drain. This water has a name, it is called ‘perched water‘, so named because it ’perches’ (like a bird) in the soil above the pot bottom. This excess water is critically important because it very quickly begins to kill roots growing near the bottom of the pot, within hours. The first roots to die are the roots that do the lion’s share of the work - the very fine roots often referred to as ’hair roots’. The longer the soil remains saturated, the larger the diameter of the roots killed. When air finally returns to this once saturated soil, roots then begin to regenerate. This takes energy and is extremely expensive to the plant in terms of that energy outlay. The plant is actually forced by chemical messengers that tell it to ’grow roots’, to direct energy that would have gone into growing more leaves, branches, blooms, fruit, or just increasing the overall mass of the plant, to replacing the lost roots.

The second thing that might happen when you water if you are using a water retentive soil is, you water in small sips to prevent root rot. It makes sense to only give the plant a little water at a time - right? That might be a workable option if you have the luxury of using water that has been processed through a reverse osmosis water filter, or if you are watering with distilled water, but regular tap water has things dissolved in it, like magnesium, calcium, iron, sulfur, and others. If you water in ’sips’, these dissolved solids remain in the soil and build up over time. This has an impact on the plant’s ability to absorb water and the nutrients dissolved in water. To illustrate the potential impact these dissolved solids have on a plant, picture in your mind what curing salt does to ham or bacon. It literally pulls water from the cells & dries out the meat. Any solute in the solution surrounding plant roots can have the same potential effect on plant cells. It can make it difficult for plants to absorb water and nutrients, it can make it impossible, and in some cases can actually reverse the flow of water so it moves OUT of cells, effectively collapsing and killing them. We commonly call this ‘fertilizer burn’, but it doesn’t necessarily have to result from an over-application of fertilizer. When people come here wanting a remedy for foliage that is dying, with dried edges & tips, it’s almost always from over-watering and the accompanying limitation that has on root function and metabolism, or a high level of dissolved solids from fertilizers and tap water having accumulated in the soil making it difficult for the plant to take up water. Misting cannot correct a problem related to over-watering or a high level of solutes in your plant’s soil. Low humidity can be a contributing factor to the common symptoms of necrotic (dead) leaf tips and margins (edges), but for the actual cause, look to impaired root function from over-watering or a high level of dissolved solids in the soil. BOTH of these conditions are nearly always linked to a poor soil.

When using water-retentive soils, it seems almost as though we are on the horns of a dilemma. If we water generously, we risk the soil remaining saturated so long it causes root rot, or at a minimum - impaired root function. If we water sparingly, in small sips, we risk an accumulation of dissolved solids from tap water and fertilizer solutions in the soil …… so what to do? Well - I think we should look at an option that solves both issues and makes things much easier for the grower, while also providing the grower with considerably more latitude when it comes to watering and fertilizing.

The factor that determines how water retentive and difficult to grow in a soil is, is the size of the particles it is made from. The smaller the particles - the greater the water retention and the greater the degree of difficulty for growers. Soils made of any combination of peat, coir, compost, sand, topsoil, and other fine particulates are going to be very water retentive, which we know is undesirable from the perspective of the plant, and they cannot be suitably amended to correct drainage or the height of the perched water by adding perlite or other drainage material. If anyone disagrees with that statement, please ask for an explanation before mounting an argument or offering individual observations. Adding perlite to soils reduces the overall water retention of the soil, but it does nothing measurable for drainage (flow-through rates) or the height of the perched water table, the later being the critical consideration when it comes to a healthy root zone.

Soils made of a high % of pine bark or other inorganic particles will have lots of large air spaces called macropores. These are pores that will not hold water, only air, even when the soil is as saturated is it can be. They are critical to a healthy root zone. If you build a soil with plenty of air space, it hardly matters what the soil is made from. What is important is how the soil is structured. I will grow a perfectly healthy plant in a bucket of broken glass on a dare and a wager if anyone is interested in taking me up on it. If you have a soil with a healthy structure, a good nutritional supplementation program, and have good available light, the rest is so easy anyone can do it - honest. I’ve seen it happen over & over and over again. You will not go wrong if your primary focus is providing a healthy - a truly healthy environment for roots. Roots are the heart of the plant. Roots come first. If you cannot keep the roots happy, there is no chance you can keep the rest of the plant happy. That was a paraphrased quote from Dr. Carl Whitcomb, PhD, who wrote the bible on “Plant Production in Containers”.

This ends the beginning discussion about soils. Until you are able to grow plants, the growth rate and appearance of which you are happy with, focusing on removing the limitations placed on your plants by soil choice will almost always constitute the best use of your energies. After reading this far, if nothing else, I hope you take that from this offering. It is the most important point and the best piece of advice I can give you. If you are interested in knowing HOW to make soils that will help you remove the limitations, now is the time to ask.

Nutrition is an area that is very misunderstood when it comes to container culture, but it is actually very easy. It’s also very easy to become confused because there are so many numbers that represent different fertilizer NPK percentages and so many different kinds of fertilizers. I will need to use some numbers, but I think an understanding of NPK percentages as opposed to fertilizer RATIOS is important. NPK %s tell us how much (N)itrogen, (P)hosphorous pentoxide, and (K) potassium oxide (the symbol for potassium is ’K’) are in a fertilizer by weight. So a fertilizer that is labeled “All Purpose 24-8-16” is 24% nitrogen, 8% phosphorous, and 16% potassium. 12-4-8 is also a common “all-purpose” fertilizer. It has exactly half the nutrients of 24-8-16, but both are 3:1:2 RATIO fertilizers. Ratios are a way of describing the amount of nutrients in a fertilizer as they relate to each other. Why is this important? It is important because we know that on average, plants use about 6 times as much N as P, and they use about 3/5 as much K as N, and now I will tell you how we can use this information to our plant’s advantage.

The ideal way to fertilize is to supply fertilizer at the same ratio in which plants use the nutrients. The reason is because optimal growth and vitality can be had only when nutrients are in the soil at overall levels low enough that it doesn’t become difficult for plants to take up water and nutrients dissolved in that water. Remember what we said above about a high level of soluble in the soil making it difficult for roots to absorb water and nutrients? Nutrients also need to be present at levels high enough to prevent deficiencies. If we think about it for a second, we can see that the best way to achieve this end is to supply nutrients at the same ratio in which they are used.

I noted that the NPK percentages actually tell us how much phosphorous pentoxide and potassium oxide are in a fertilizer so I can show you how fertilizer manufacturers arrived at a 3:1:2 ratio as their “all-purpose” blend. Only 43% of the P reported on a fertilizer label is actually P, and only 83% of the K reported is actually K. Once you apply these factors to any of the 3:1:2 ratio fertilizers (24-8-16, 12-4-8, and 9-3-6 are all popular 3:1:2 ratios, you’ll see they supply nutrients in almost exactly the same ratios as the average that plants actually use, and these fertilizers are excellent at keeping overall levels of soluble as low as they can be without nutritional deficiencies.

There is no need to use specialty fertilizers; and many specialty fertilizers, like the advertised “bloom boosters” with up to 30 times more phosphorous than a plant could ever use (in relation to the amount of N used) can be moderately to severely limiting because the excess nutrients are a limiting factor.

The question often arises, “Should I use a synthetic or an organic fertilizer”? The answer is: Use whichever you wish; but the qualifiers are: Organic fertilizers are actually more accurately called soil amendments. They are mixed into the soil in the hope that at some point soil organisms will digest them and make them available in elemental form so plants can absorb them. The problem with that approach is that the populations and activity of soil life populations in containers are erratic and unreliable, making the delivery of nutrients from organic sources just as erratic and unreliable. What you apply today, may not be available until next month, and there is no way to determine what residual amounts of which elements remain in the soil. Soluble fertilizers like Miracle-Gro and others are completely available as soon as applied, and we know exactly what our plants are getting. They are simply much easier to use and deliver nutrients much more reliable than other fertilizer types. You can lump controlled release fertilizers like Osmocote and others in with the soluble synthetic fertilizers. With them, you get an extra measure of convenience but sacrifice a measure of control. As with all fertilizers, it is important to note the NPK percentages to be sure you are supplying the fertilizer in a favorable ratio if you want your plants to be all they can be.

It isn’t going to kill your plants if you use a fertilizer with a less favorable ratio because plants tend to take the nutrients they need from the soil (solution) and leave the rest, but it is important to understand that it is ’the rest’ that constitutes a limiting factor, so avoiding excessively high levels of any one nutrient whenever possible is to your (plant’s) benefit.

As noted above, most growers draw no distinction between ‘repotting’ and ‘potting up’. I have spent literally thousands of hours digging around in the root-balls of containerized plants. Old plants from nurseries of greenhouses are probably the closest examples to what most houseplants are like below the soil line, so I'll offer my thoughts for you to consider or discard as you find fitting.

I have helped salvage many plants that had been containerized for long periods and were ‘circling the drain’. Not long ago, our bonsai club invited a visiting artist to conduct a workshop on mugo pines. The nursery (a huge operation) where we have our meetings happened to have purchased several thousand of the mugos somewhere around 10 - 12 years ago and they had been potted up into continually larger containers ever since. Why relate these uninteresting snippets? In the cases of material that has been progressively potted-up only, large perennial roots occupied nearly the entire volume of the container, plant vitality was in severe decline, and soil in the original root-ball had become so hard that in some cases a chisel was required to remove it.

In plants that are potted up, rootage becomes entangled. As root diameters increase, portions of the roots constrict other roots and impair the flow of water and nutrients through them, much the same as in the case of girdling or encircling roots on perennials grown in-ground. The ratio of fine, feeder roots to more lignified (woody) and perennial roots becomes skewed to favor the larger, and practically speaking, useless roots.

The initial symptoms of poor root conditions are progressive diminishing of branch extension on plants that branch, loss/shedding of foliage on the parts of branches nearest to the ‘trunk’, often giving the plant a ‘poodle look’, and reduced vitality. As rootage becomes continually compressed and restricted, branch extension stops and individual branches might die as water/nutrient movement is further compromised. Foliage quality may not (important to understand) indicate the tree is struggling until the condition is severe, but if you observe your plants carefully, you will find them increasingly unable to cope with stressful conditions - too much/little water, heat, sun, etc. Trees that are operating under conditions of stress that has progressed to strain, will usually be diagnosed in the end as suffering from attack by insects or other bio-agents/disease while the underlying cause goes unnoticed.

I will mention again that I draw distinct delineation between simply potting up and repotting. Potting up temporarily offers room for fine rootage to grow and do the necessary work of water/nutrient uptake, but these new roots soon lignify, while rootage in the old root mass continues to grow and become increasingly restrictive. The larger and larger containers required for potting up & the difficulty in handling them also makes us increasingly reluctant to undertake even potting up, let alone undertake the task of repotting/root-pruning, which grows increasingly difficult with each up-potting.

So we are clear on terminology, potting up simply involves moving the plant with its root mass and soil intact, or nearly so, to a larger container and filling in around the root/soil mass with additional soil. Repotting, on the other hand, includes the removal of all or part of the soil and the pruning of roots, with an eye to removing the largest roots, as well as those that would be considered defective. Examples are roots that are dead, those growing back toward the center of the root mass, encircling, girdling or j-hooked roots, and otherwise damaged roots.

I often explain the effects of repotting vs potting up like this:
I will rate growth/vitality potential on a scale of 1-10, with 10 being the best. We're going to say that plants in containers can only achieve a growth/vitality rating of 9, due to the somewhat limiting effects of container culture. Lets also imagine that for every year a plant goes w/o repotting or potting up, its measure of growth/vitality slips by 1 number, That is to say you pot a plant and the first year it grows at a level of 9, the next year, an 8, the next year a 7. Also imagine please, we're going to go 3 years between repotting or potting up.

Here's what happens to the plant you repot/root prune:
year 1: 9
year 2: 8
year 3: 7
repot
year 1: 9
year 2: 8
year 3: 7
repot
year 1: 9
year 2: 8
year 3: 7
You can see that a full repotting and root pruning returns the plant to its full potential within the limits of other cultural influences for as long as you care to repot/root prune.

Looking now at how woody plants respond to only potting up:
year 1: 9
year 2: 8
year 3: 7
pot up
year 1: 8
year 2: 7
year 3: 6
pot up
year 1: 7
year 2: 6
year 3: 5
pot up
year 1: 6
year 2: 5
year 3: 4
pot up
year 1: 5
year 2: 4
year 3: 3
pot up
year 1: 4
year 2: 3
year 3: 2
pot up
year 1: 3
year 2: 2
year 3: 1
This is a fairly accurate illustration of the influence tight roots have on a plant's growth/vitality. You might think of it for a moment in the context of the longevity of bonsai trees vs the life expectancy of most trees grown as houseplants, or the difference between less than 4 years versus more than 400 years, lying primarily in how the roots are treated.

I have not yet mentioned that the dissimilar characteristics of the old soil as compared to the new soil when potting-up also carries the potential for trouble. With a compacted soil in the old roots and a fresh batch of soil surrounding the roots of a freshly potted up plant, it is nearly impossible to establish a watering regimen that doesn't keep the differing soils either too wet or too dry, both conditions occurring concurrently being a limiting factor and the rule rather than the exception.

Most who read this would have great difficulty showing me a containerized plant that is more than 10 years old and as vigorous as it could be, unless it has been root-pruned at repotting time; yet I can show you hundreds of trees 20 years to 200 years old and older that are in perfect health. All have been root-pruned and given a fresh footing in in new soil at regular and frequent intervals, the same treatment all my houseplants get.

Thanks to any/all who made it this far. This is only an overview, but with even a rudimentary understanding of how to go about reducing the effects of the limiting factors that restrict growth and vitality, I know you can improve on how well your plants can grow, as well as on the degree of satisfaction you get from your growing experience - my only reasons for writing this. Hopefully the offering leaves you with many questions.

Al

You might find this link to more detailed information about soils helpful:
http://davesgarden.com/community/forums/t/1073399/


This message was edited Oct 19, 2011 5:09 PM

This message was edited Oct 19, 2011 5:46 PM

Hi Tapla,
I am new to gardening of all kinds. I am using your 'gritty mix' for all of my indoor plants as well as Dyna-Gro Foliage Pro and they are all thriving. I plan to start some perrenials and annuals from seed this coming winter/early spring for next years outside container and landscape plants. Can I use the 'gritty mix' as a seed starting medium or is there an alternative that you could recommend. I want to use a mix that provides high germination rates as well as minimizes, or preferably, prevents damping off. This is my first time starting seeds. Please help!!!
Thanks,
Linda

Hi, Linda. Thanks for helping to get the thread of the ground. I was beginning to wonder .... ;-)

The two primary considerations when starting most seeds are a steady supply of moisture and a medium that doesn't support the fungaluglies that cause damping off diseases (phytophthora, pythium, Rhizoctonia solani .....). A 'steady supply of moisture' would be enough moisture to keep the medium 'damp but not wet' - about as damp as a wrung-out sponge is great. Soggy soils that don't hold enough air become the breeding ground for the listed fungi + others that cause the damping off diseases. Seedlings LOVE air in the root zone - LOTS of it. Ideal, would be a coarse medium like the gritty mix or a bark-based mix that would ensure good aeration - because it is literally built into the soil. I often use either the gritty mix or the 5:1:1 (pine bark:peat:perlite) mix to start seeds. What I usually do is start with at least 3" of medium. Spread seeds on top of the medium, then cover the seeds with a thin layer of peat (5:1:1) or Turface fines (gritty mix). I then mist the surface regularly to keep the moisture supply even and to guard against soggy soil which is the real killer.

Commercial seed starting mixes rely on the fact that the mix is made from peat, which has such a low pH that it is almost sterile, and vermiculite, which would be considered sterile because it is fired at such high temps. The problem with these mixes is the fact that they are VERY water retentive, compact easily, and rely on the good watering sense of the grower to keep the medium properly moistened, which as we know doesn't always work out according to intent.

Most seeds germinate fastest at temps from 65-70*. Air temperatures somewhat cooler (about 10*) than root temperatures seems to promote best seedling growth, so a propagation mat (sort of a waterproof heating pad for hort applications) used up to the onset of seedling emergence (then discontinue bottom heat) is helpful as long as soil temps don't get too high above 70*. Begin fertilizing when the first set of true leaves appears; until then, the seedling gets its nutrition from the seed's endosperm.

Al

This message was edited Oct 26, 2011 11:02 AM

Good Morning Al,
Thanks again for all the expert help. You've made seed starting so clear and simple. I was so confused by all of the different methods discussed on the seed germination forum. I now look forward to propagation.....which says alot coming from a former "double-dipped brown thumb".
Linda

You're welcome - my pleasure. Don't forget asexual propagation from cuttings, air or ground layering or even stooling, and divisions, as a way to make more plants. I often pinch many of the plants I buy as soon as I get them & use the cuttings to start more plants for myself or to share.

Best luck.

Al

I too enjoyed your messages on beginning houseplants. This fall I am planting more seeds than in the past simply due to over half of my seeds did not develop.
I did plant ornamental kale in the beginning of Sept. with not much success. I am planning on trying again this weekend. I am using seed starter soil and viable seeds from Twillyseeds.com. It is a challenge to keep the right moisture at all times. I do have a greenhouse to use if the weather gets a little too nippy.

I do appreciate the kind words, Peg. I try hard to make sure you guys get information you can rely on as scientifically and horticulturally sound - so you at least can make informed decisions when they're necessary. I realize that not everyone wants to put the same amount of effort into growing and learning, but a little effort and a little knowledge can go a long way toward making us better growers. Hopefully this thread ends up being a place folks feel they can come to for help departing from limiting habits, instead of encouragement to change something minor and go on with business as usual.

Thanks for your comments and good luck with the kale. What are you planning on using for fertilizer?

Al

Schefflera

Hm, I've always been told NOT to mess with the roots... I'm about to repot some of my plants... How do you cut roots back? How do you know which ones, and how do you get to the ones in the center of the root ball? Or am I reading this wrong? I have a healthy Ficus Benjamina, and I can just see it dropping every last leaf if I cut the roots back so much...

There is a LOT of misinformation that is perpetuated by people who don't really understand why they parrot what they heard or read somewhere. That you should never 'mess with roots' is one of those horticultural myths that when looked at from a more scientific perspective, won't hold up to even casual examination.

Cases in point from the practical perspective: I have some 300 plants growing on as potential bonsai. They ALL regularly (every year or every other year is the norm) have anywhere from 1/3 - 3/4 of their roots removed for the express purpose of eliminating the limiting effect of tight roots and to rejuvenate the plant. Large roots in the root mass of containerized plants serve no purpose other than as conductive plumbing. It's the fine roots that do all the heavy lifting, so anything you do that increases the number of fine roots increases growth and vitality. How do you increase the number of fine roots? The same way you increase the number of fine branches in the canopy - by pruning and pinching.

Also - in spring, when I'm building the 30-40 mixed display containers I have scattered through the decks & gardens, I'll use a lot of bedding plants & plants in 3-4" containers. Often, these plants are VERY root bound. Recognizing the permanent negative effect that condition has on plants, I immediately correct it as a matter of course by ripping the bottom 1/2 - 2/3 of the roots off the plant and running my fingers up into the root mass to separate and spread roots before the plants are potted in the mixed (or specimen/singular) plantings. I also treat all plants I buy in similar fashion. I've posted thousands of pictures here & at Garden Web that show a very wide variety of plants that are obviously robust and exhibiting unblemished foliage & prolific blooms - so it works. 'Root work' is the reason bonsai trees can be passed from generation to generation in perfect good health, while most houseplant growers have great difficulty pointing to a plant more than a few years old that could be considered in excellent or even good health.

The rest of the reason 'why': We already saw that pruning roots increases the number of fine roots that do all the heavy lifting, But there is another factor involved. We tend to think of the age of plants in the same manner we think of age in humans or animals - chronologically. We, like plants, go through several life stages - embryonic, juvenile, adolescent (intermediate in plants), and mature, are stages roughly mirrored in plants. Where we vary greatly is in the way our cells age. In animals, body cells all mature at approximately the same speed. Plants grow by consecutive divisions of cells at the growing points (meristems), so their various parts are different ages (the top of the plant is younger than the basal portion, chronologically, but older ontogenetically because it took more cell divisions for the part of the plant to be at the top or the end of a branch.

Why is that important? Because tissues tend to RETAIN their genetic vigor. That is to say tissues growing nearest to the point where the top of the plant transitions to roots are the most vigorous tissues and they retain that vigor. So, when you cut a plant back hard, you cut it back to more vigorous tissues. Often, growth will 'explode', with the plant back-budding profusely when you cut it back hard. This holds true as much below the soil line as above.

You may be familiar with the practice of 'rejuvenation pruning that is undertaken to restore the vigor of plants in the landscape. The term comes from the fact that this type of pruning restores the plant to a point where it is growing from more juvenile tissues. It shouldn't be much of a surprise to learn that roots as well as shoots can be rejuvenated by way of the same mechanism.

We KNOW that once roots become congested to the point the root/soil mass can be lifted intact, that growth and vitality are impacted negatively, which is why potting up (as seen in the OP) is a limiting practice and repotting with its accompanying root work rejuvenates.

If you have any other questions, or there is anything you're not clear on, please don't hesitate to ask. I admire anyone who wants to learn & isn't afraid to ask questions.

Al

For the Kale, I thought I would use the root stimulant that I have for 2-3 weeks then possibly use the Miracle Grow on hand.

Hm... OK, I get it... But, do you still pot in a bigger pot that the plant was in after you cut the roots back? When you cut the roots back, do you only do it when you are putting the plant in a bigger pot, or just when that 1-2 year mark hits? Again, sorry if you already answered this..

Peg - you probably won't get any benefit from the root stimulant, but ..... What are the NPK% of your fertilizer?

TR - I'll end with some thoughts on what REALLY determines what size pot is appropriate for what size plant. You'll be surprised to learn it's the soil - not how big the plant is or the size of the pot it was last in.

2 things determine whether or not a repot with root pruning is in order is 1) is it an appropriate time to do a full repot. Almost all houseplants, unless winter growers, are best repotted in the summer, in the month prior to their most robust growth. 2) how congested the roots are, and how congested they are GOING to be when the next appropriate time to repot rolls around. Growth becomes affected at about the state of root congestion where the root/soil mass can be lifted from the container intact. A reasonable guideline would probably be found in asking yourself this question at the appropriate time for repotting, "Will the plant reach that point of root congestion before it's less than half way through its most vigorous growth period?" If the answer is yes, it should probably be repotted. If the answer is no, it can probably wait another year.

In many cases, repotting (as opposed to potting up) allows you to use the same pot for a number of years before the plant outgrows it. You remove the old soil, reduce the roots by 1/3-2/3, and put the plant back in the same pot in fresh soil. After only a few repots, you'll know intuitively when the plant needs a larger pot. Which is the perfect lead-in to what determines appropriate pot size.

Here's a copy/paste job of something I wrote a while back:
How large a container ‘can’ or ‘should’ be, depends on the relationship between the mass of the plant material you are working with and your choice of soil. We often concern ourselves with "over-potting" (using a container that is too large), but "over-potting" is a term that arises from a lack of a basic understanding about the relationship we will look at, which logically determines appropriate container size.

It's often parroted that you should only move up one container size when "potting-up". The reasoning is, that when potting up to a container more than one size larger, the soil will remain wet too long and cause root rot issues, but it is the size/mass of the plant material you are working with, and the physical properties of the soil you choose that determines both the upper & lower limits of appropriate container size - not a formulaic and zombie-like upward progression of container sizes. In many cases, after root pruning a plant, it may even be appropriate to step down a container size or two, but as you will see, that also depends on the physical properties of the soil you choose.

Plants grown in ‘slow’ (slow-draining/water-retentive) soils need to be grown in containers with smaller soil volumes so that the plant can use water quickly, allowing air to return to the soil before root issues beyond just impaired root function/metabolism become a limiting factor. We know that the anaerobic (airless) conditions that accompany soggy soils quickly kill fine roots and impair root function/metabolism. We also know smaller soil volumes and the root constriction that accompany them cause plants to both extend branches and gain o/a mass much more slowly - a bane if rapid growth is the goal - a boon if growth restriction and a compact plant are what you have your sights set on.

Conversely, rampant growth can be had by growing in very large containers and in very fast soils where frequent watering and fertilizing is required - so it's not that plants rebel at being potted into very large containers per se, but rather, they rebel at being potted into very large containers with a soil that is too slow and water-retentive. This is a key point.

We know that there is an inverse relationship between soil particle size and the height of the perched water table (PWT) in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water. If there is no perched water, the soil is ALWAYS well aerated, even when the soil is at container capacity (fully saturated).

So, if you aim for a soil (like the gritty mix) composed primarily of particles larger than 1/16", there is no upper limit to container size, other than what you can practically manage. The lower size limit will be determined by the soil volume's ability to allow room for roots to ’run’ and to furnish water enough to sustain the plant between irrigations. Bearing heavily on this ability is the ratio of fine roots to coarse roots. It takes a minimum amount of fine rootage to support the canopy under high water demand. If the container is full of large roots, there may not be room for a sufficient volume of the fine roots that do all the water/nutrient delivery work and the coarse roots, too. You can grow a very large plant in a very small container if the roots have been well managed and the lion's share of the rootage is fine. You can also grow very small plants, even seedlings, in very large containers if the soil is fast (free-draining and well-aerated) enough that the soil holds no, or very little perched water.

I have just offered clear illustration that the oft repeated advice to ‘only pot up one size at a time’, only applies when using heavy, water-retentive soils. Those using well-aerated soils are not bound by the same restrictions.

Al

Thank You for this thread Al. I printed it and took my time reading it and have enjoyed the learning. I now need to find your other threads on soil and copy them. I did have a question on pruning to compensate for the artificial light I have to provide for some of my plants in the winter. I'm always afraid to prune for fear I will kill them. Needless to say come spring when they go outside I deal with long leggy plants that I know need pruned.
Acts

Actually, I was just asked (a couple of days ago, over at Garden Web) to start a thread about the very basic concepts of pinching & pruning - about what happens when you DO pinch or prune and how to use it to your advantage, and how to use it to keep YOU in control instead of the plant. There really is no reason to have an unruly plant sprawling hither and yon, when all it takes is a rudimentary understanding of how 2 growth hormones work against one another (antagonistically) in a fight for control of how the plant will grow, and a little intervention on our part to tip the scales gently in favor of one or the other. ;-)

For now though, it's probably better to think 'pinching' from Aug-Jun, and any hard cutting back or heavy pruning from Jun-Aug. It's important to take into account the plant's energy levels and energy flow when you start do do anything drastic. Plants are VERY forgiving if you give them a chance to gather their reserves before you heap indignities on them - not so forgiving if you don't consider how strong they are (or aren't) and just go about things willy nilly.

It doesn't take much effort to gain a little understanding about how plants work; and the knowledge you claim will serve you for as long as you tend plants. I guess you could say that knowledge is a gift that keeps on giving - especially when you 'pay it forward'.

Al

I have so enjoyed this thread. thank you

It was quiet for so long, I was afraid it wasn't going to take off.

You had mentioned the other threads about soils & I forgot to post a link. You'll find 2 older threads as stickies at the top of the container gardening forum, but this is an extension of those threads. I guess they were getting so long they were slow to load for some, so they asked for a continuation. Here's the thread that's most recent, even though no one's requested it be made a sticky yet: http://davesgarden.com/community/forums/t/1073399/

Thanks again for the kind words!

Al

What about plants 'liking to be root-bound'? ( I 've read that about Philodendrons )Another myth, or true? How does the root trimming fit their needs if it's true?

MYTH - with a small qualifier. Here is something I wrote a while back that hopefully dispells the myth and explains why it's parrotted and perpetuated so widely:

I would like to talk a little about, and hopefully dispel the myth that certain plants 'like' or 'prefer' to be grown tight (under root-bound conditions). Maybe we can also understand that no plant will 'do well' when it's pot-bound if you are using a plant with plenty of room for its roots to run as your standard of judgment. If plants did better growing under root-bound conditions, Mother Nature would have arranged for in situ (where they naturally occur) plants to grow with their roots in tight little cones or cubes, yet we never see that occur. While it's true that we may be sometimes be able to use the STRESS of our plants being root-bound to bend plants to our will and achieve OUR goals, the fact is that this serves US well, and not the plant.

Let's examine what 'growth' is. Growth is simply a measure of the increase in a plant's biomass, how much bigger it has become (the weight of the sum of its parts), and is the actual measure of how 'well' a plant is doing. We know that tight roots restrict growth, reduce the amount of branch/stem extension, and reduce the potential for an increase in mass, so even if we THINK plants are doing well because we use the stress of tight roots to get them to bloom or grow in a particular habit that we like, the truth is tight roots are stressful, and plants would rather have plenty of room for their roots so they could grow as mother nature intended. No one is more aware of the negative influence tight roots has on growth than the bonsai practitioner who uses that tool extensively to bind down the plant's growth habits so the will of the grower, not the plant, prevails. Using tight roots as a tool to achieve an end is all about the grower's wants, and not the plant's.

Interestingly, many mistake the fact that a plant seems to be extending and growing leaves for actual growth, but if the plant is robbing nutrients from other parts and then shedding them in order to support new leaves or branch extension, it may not be increasing in mass, and therefore not growing ..... only robbing Peter to pay Paul.

If we chase the 'root-bound issue' a little further, we can see the reasons that it is suggested that particular plants might like root-bound conditions. Tight roots alters the plant's growth habits, and the stress of tight roots can cause other physiological responses, like bloom induction. Again, this is happening because of stress, and is the plant's unhappy response. Bright flowers make the grower happy, but the plant's perspective may be entirely different.

Where I was really heading when I started to write this is: There is a relationship between plant mass (size), the physical characteristics of the soil, and the size of the container. In many cases, when we are advised that plant X prefers to be grown tight, we are being told that this plant won't tolerate wet feet for extended periods. Someone somewhere assumed that we would be growing this plant in an out-of-the-bag, water retentive soil, and "a big pot of that soil stays wet for a long time, so we better tell these people to grow this plant in a tiny pot so the plant can use the water in the soil quicker; then, air will return to the soil faster and roots won't rot."

If you place a plant in a gallon size pot of water-retentive soil, it might use the water fairly quickly, at least quickly enough to prevent root rot; but if you put the same plant in 5 gallons of water-retentive soil, the plant will take 5 times as long to use the water and for air to return to the soil, making it much more probable that root rot issues will arise. So lets tell 'em to grow these plants tight to save them (the growers) from themselves ......... because we KNOW they're all going to be using a soggy soil.

The key here, is the soil. If you choose a very porous soil that drains well and supports no (or very little) perched water (perched water is that water in the saturated layer of soil at the bottom of the pot), you can grow a very small plant in a very large pot and make the plant MUCH happier than if you were growing it tight. You still have the option of choosing those plants you prefer to stress intentionally (with tight roots) to get them to grow as YOU please; but for the others, which comprise the highest %, it makes much better sense to change to a soil that allows you to give the plant what it wants (room for roots to run) than to stress the plant (with tight roots) so it won't die (from root rot due to an excessively soggy soil). That's a little like keeping your dog in a sleeping bag 24-7 to ensure he doesn't get cold.

Al

Hi Al, Where do you prchase or find the growing mediums you use. Do I find the fir bark at a place that makes mulch ? Can I get the chicken grit at a farm store and we have a stone and rock quarry close. Can I find the Turface there. I'm really interested in this, you have posted some amazing pictures.
Thanks
Acts

I make all my own mediums, but I basically use 2. The reason I use them is they are much easier and much more productive. I don't need to worry about over-watering, root rot, or a build-up of salts in the soil from tap water & fertilizers.

Easiest to make is the mix based on pine bark fines. It consists of:
5 parts pine bark fines
1 part perlite
1 part sphagnum peat (or compost)
dolomitic (garden) lime @ 2-3 tsp per gallon or 1/3-1/2 cup/cu ft

When you're done, it will look like the mix in the middle (when dry). It's coarseness lends plenty of aeration to the soil and reduces or practically eliminates perched water, which is the real culprit, and normally the most limiting factor for growers using commercially prepared soils based on peat. Perched water in soils simply makes your job soo much more difficult .... you end up fighting against the effects of the soil instead of letting the soil work FOR you.





PS I like 1631, too ;-)

The bark you see in the picture above is what you need to look for. Unfortunately, the size of the bark is important, and it often takes some scouting to find something suitable. When it comes to deciding what soils are top notch and what soils are inappropriate to best vitality, size (of the particles) matters. I'll wait for questions before I go deeper, but I hope any others that are curious will consider joining in the conversation. I really think that beginners can take a giant step forward if they learn to get the soil right.

The gritty mix is what I use for all my houseplants and material growing on as bonsai, as well as my bonsai. It's a very coarse mix that looks more like gravel with a little bark in it, but it has terrific structure, it's really durable (lasts a LONG time) and super easy to grow in. I think it's important to understand that 'rich and black' soils are wonderful in the garden, but are often too water retentive to be well-suited to container culture. Container soils are all about structure. If you keep in the back of your mind that ensuring there is plenty of air in the soil for as long as the planned interval between repots is your #1 priority, you have it ...... as long as you learn how to do it and follow through.

The gritty mix (These soils were named by others after they started using them. Both have a very large following, more so at Garden Web than here, but you can see how popular the information is by noting the degree of participation on the threads devoted to a discussion about soils on the Container Gardening forum.) is also comprised of 3 ingredients:
1 part of screened pine or fir bark
1 part screened Turface
1 part crushed granite or cherrystone (chicken grit in grower size or #2 cherrystone)

You should be able to get the Turface at John Deere Landscapes, 2020 Kelsey Ct in Fort Wayne, (260) 490-0041

The grit can be found at feed stores & grain elevators with stores that sell farm feeds. Skip the big box stores for Turface or grit. They might have suitable bark, but that's a deal where you find it when you find it. I have several places within a few miles where I can get it whenever I need it. For the gritty mix, I buy prescreened fir (orchid) bark in 1/8-1/4" size, but screened pine bark works just as well.

I think it's important to realize that it's not the 'recipes' that are of value, it's the concept found in the information I linked you to. The recipes are just good ways to implement the concept.

What I use for my houseplants & bonsai:

Al

Thanks so much, I think what I'll do is start collecting all the mediums this winter and I'll be ready in the spring to do my repotting. I was buying cactus mix and that seemed to work pretty good. I did notice after reading about the PWT that I had a few plants this year that were rotting because of it...Wonderful Information! :) :)

Acts

This is so much good information, thank you for posting, Al. I have a lot of houseplants, the hubby takes care of them. I can see that while they are doing ok, they are not thriving.

He was always the 'inside guy', I took care of the outside stuff. The more I looked at the inside plants, the more I realized they weren't doing as well as they could. And then you started this thread.

I look forward to spring, and in the meantime will read all this good information you have been posting, and that I have printed out.

Thanks again!
Smiley/Julie

Thank you, Julie & Acts (did you ck 1631?). I think there are a lot of growing practices that could nearly be labeled 'traditional' that have built in limitations. The primary one is the tendency of beginners and experienced alike to grow in soils they can readily buy off the shelf. I'm not saying that you absolutely can't grow well in soils based on peat, compost, or other small particulates; it can be done, but it is much more difficult and takes a degree of understanding of soil science and plant physiology that isn't in the grasp of most hobby growers.

I think I mentioned that the soil is the foundation of every planting. Build a strong foundation, and you won't have to fight against the ill effects of a weak one down the road. I remember a commercial for an auto parts manufacturer from years ago. I think it was Framm. They were trying to get you to purchase their air and oil filters by using the motto, "You can pay me now [the screen changes to a greasy-looking mechanic] or you can pay me later." Growing houseplants is much like that. If you start with a poor soil, you'll be scratching your head and wondering how to fix the issues that arise from that choice, most of the time not even realizing the true source of those issues. If you start with a good soil, in most cases those same issues never surface. It is an extra effort to locate the ingredients & mix your own soil, though it is very easy and about half the cost of bagged soils, but you get the trade off of making the effort up front instead of later. You end up saving the expense of buying new plants, increase the amount of satisfaction you get from your growing experience, and you get to look at healthy, disease/insect-free plants that grow well.

Just to remind anyone listening in, the discussion isn't limited to soils. If there are other issues you'd like to discuss, feel free to comment or ask questions. I'm sure that there are others wondering the same thing(s) you are.

Does anyone have a guess as to what plant this bonsai I'm working on is? Hint: It's not a tree.

Al

The leaves look like an adenium, if it is I bet its beautiful in flower. You asked if we checked 1631, I'm sorry but I don't know what that is.

Does this help, Acts? 16:31 If you don't get it yet, Dmail me. ;-)

Here's the plant before pruning. It's a dwarf snapdragon (Chaenorrhinum minus). Just a common garden variety.

Al

Oh My Gosh!!! That is Sooo Awesome. To take an ordinary plant that would grow and flourish without much help and to use you knowledge of soil,water,nutrients and light to make it more than just a snapdragon. That is really something.
Reminds me of the parable of the sower in Luke 8

How often do you have to water using the "Gritty" mix?
That Snapdragon is awesome! I had no idea...

Thanks, guys. You can do things like that with many other plants, too. I often grow Coleus, many herbs, Impatiens, ..... into bonsai shapes in 1-2 growing seasons. It's fun. Which leads me to say that there really is no reason you have to accept the way your plants grow. Often we buy a plant with the goal in mind we want it to "grow big", but then what? In my travels, I'm in peoples homes every day doing estimates (I own a glass company). I get to see their plants. Very rarely do I see a plant that has been pruned or pinched properly. I think our focus would be better if it was centered on keeping the plant healthy and appealing to the eye, with a heavy emphasis on healthy. In order to do that, as in any undertaking we wish to do well, we might need to make an extra effort. I very often note that what's best for the plant and grower convenience are often mutually exclusive. You can take the approach that 'I'm going to plant this plant in something I can buy inexpensively' or you can make the effort to find the ingredients and make a soil that really will make a very big difference in your abilities to keep plants happy.

I grow under lights in the winter, with most of my plants being in much smaller volumes of soil than what most of you are used to, and I water most plants every 3 days. Because the gritty mix holds very little water BETWEEN the particles (almost all of it's water retention comes from the water held in internal particle pores) you need to water more often. THAT, is a good thing. When you water, it forces unhealthy gases from the soil and pulls fresh air in. The gritty mix already has excellent gas exchange (probably a new term for most) because of its high porosity, but the extra waterings regularly flushes CO2, methane, and sulfurous gasses that tend to accumulate in heavier soils that hold perched water. These heavier soils produce a considerably larger volume of these gasses than soils with greater air porosity, too.

Al

Al, are we supposed to guess at that bonsai you have there? If so, I humbly submit that it looks like a geranium to me.

I mentioned to my husband that next spring his plants are mine ~all mine! After reading, and rereading the above, I can't wait to take a look at what lies beneath the soil in our houseplants.

I just skimmed your posts on your original thread hoping to retain some of this, but have forgotten what CRF is.

I found it! Controlled Release Fertilizer.

SM - I didn't post intending that you'd guess at what it was, but since you did, you'll be pleased to know you're right, it's a dwarf geranium, species forgotten or never known.

Is everyone clear on the different kinds of fertilizer & how they work? .... and a big question - how to choose an appropriate fertilizer?

Al

Hello..It's me again. I don't know about anyone else but I would love a run down on fertilizers. I've bought every kind there is. I seem to remember you explained fertilizer on another thread but can't find it...
Acts

Yeah, I was concentrating on good soil structure myself. The fertilizer got past me.

Ok - Soil structure will probably have the most significant impact on your success; that is to say, on your ability to consistently produce healthy plants that grow well. Light is very important, too, but there isn't much you can do about light, other than supplement it or move plants to where light levels are most appropriate. As important as light is, it usually gets short shrift for the reason stated. Nutrition is very important, too. I covered the basics in the OP, so if there are questions after reviewing it, please feel free to ask.

With CRFs (controlled release fertilizers) the water-soluble fertilizers many of you are accustomed to have been modified to slow the release characteristics of the nutrients. There is no official differentiation between slow-release and controlled-release fertilizers,
but we can make a simple differentiation. The granule fertilizers we often use on our lawns & gardens are 'slow release'; because they have polymer chains that are gradually broken off by microbes & made available for roots to uptake. Moisture, time, and microbial populations drive availability of these granular & marginally soluble fertilizers.

The term 'controlled release' fertilizer (CRF) should be reserved for fertilizers that are encapsulated or coated. Just think of a Tootsie Pop sucker, with an outer coating of candy and the good stuff inside. CRFs are much the same, with the trick being how to get the good stuff to pass through the coating so plants can take it up.

That's made to work by making the coating permeable. That means water can pass through, and it DOES pass through because water is attracted to salts. When the water passes into the prills (pellets) some of the nutrients are dissolved. How much can be dissolved is controlled by the TEMPERATURE. If the Tootsie Pop was in a cold refrigerator, the Tootsie Roll center would be reluctant to dissolve, but as it gets warmer (like when you suck on a Tootsie Roll for a while) it starts to dissolve. This is what drives the release of nutrients in CRFs. By varying the coating thickness, the interval over which the nutrients are released can be varied - 3 month, 4 month, 6 month, 9 month, are all popular formulations.

I prefer soluble fertilizers like Miracle-Gro, Peter's, Jack's, others. My Favorite is Foliage-Pro 9-3-6. It is a 3:1:2 RATIO fertilizer, so it comes closest to supplying nutrients in the same ratio plants use them, a decided plus (review the initial post for more). They give you much greater control than either CRFs or slow release fertilizers. Try to avoid any fertilizers that have a middle number higher than the first or third numbers. They supply much more P(hosphorous) than the plant can use. In a recent conversation with the CEO of one of the companies I just listed, he confirmed the lack of need for 'special' fertilizers for practically any plant you might grow, citing the 3:1:2 ratio fertilizers as being what should be the 'go to' fertilizer for practically all plants. We also discussed the folly in using fertilizers (in containers) that often supply up to 30X the P a plant could ever use (as in the commonly seen "bloom-boosting" formulation 10-52-10), indicating that the only reason for producing them was that people have been tricked into using them, and if they aren't produced they lose market share.

The best all purpose fertilizer I've found is Foliage-Pro 9-3-6. It supplies ALL nutrients essential to normal growth in the ratio used by plants (on average), and it derives about 2/3 of it's Nitrogen from nitrate sources. This is a plus for any plants grown in low light because nitrate N helps to keep internodes (the distance between leaves) short, so plants look fuller & don't get as leggy. My second choice would be Miracle-Gro 12-4-8 in liquid form (because it's so easy to mix & use), then any brand of granular soluble fertilizer in 24-8-16. MG, Schultz, Peters, Jacks ..... all make 24-8-16. All these fertilizers listed have 3:1:2 RATIOS, even though the NPK %s are very different. It's the RATIO that is most important - not the NPK %s. Review the OP for more.

Al

That makes more sense Al, thank you. So the Miracle-Gro I now use is fine.

Thank you, Al. You've given a lot of very good basic information. I'd like to share your findings with the Nightbloomers, the evening branch of the Cocoa Beach Garden Club. May I have your permission to copy and print out your Overview for beginners?
mittsy

SM - what are the NPK %s of the MG you are using. You'll find it in small print on the side of the box. If it's 24-8-16, or if it's in a yellow jug it will be 12-4-8. If you're using 20-20-20 or other NPK formulations, you could do better. If you're using any of their formulations with P as the highest number (middle number), I'd suggest you switch to 24-8-16 or 12-4-8.

Mittsy - I'm often asked by club representatives & authors for permission to use things I've written in newsletters or other work. I always say yes, but do ask that I'm credited: first/last name, city/state, email addy. Just send a D-mail & I'll provide the info. I'm flattered that you found enough value in what I said to want to share. Thank you.

Al

I can't believe that you grow things in the pots you do. It is amazing!! Can't wait to get busy in the spring with all this information. thanks

Acts