Container Soils and Water Movement in Containers (long post)

Hi Al,

What kind of lime do you use and what about substituting dolomite (calcium-magnesium carbonate) for the regular lime?

What about using turkey grit in place of sand? I have tried this with good results in both bark-based and CHC based mixes.

I use pelletized dolomitic lime. I use crushed granite (turkey grit) extensively in my soils for woody plants, but find it unnecessary in short term soils (display or veggie plantings) where perlite is much less expensive & entirely adequate.

This year, I'm experimenting with gypsum as a Ca source & will occasionally use Epsom salts for Mg.

Turface on left, crushed granite on right. Disregard soil. It's from my raised beds and would hold too much water to be suitable for use in containers.

Al

bump...some great info in here!

I totally agree. I would be nice for it to be a "sticky" on this forum.

Judy

Rather than start a new thread, I'll just bump this one -- looks like a whole lot of good information to digest here. . . .

thanks for bumping it... now "I" have questions...

what is "pine bark fines"
why do you use lime?

Pine bark fines are small chunks of pine bark that vary in stages of decomposition from partially composted to raw & uncomposted. They usually come in 2 or 3 cu ft bags & are quite inexpensive. They are often sold as mulch, or soil conditioner, so you need to look for them by product description, not by a particular product name.

Lime is a Ca (calcium) source - usually always deficient in container soils.

Al

but doesn't lime also make soil either alkaline or acidic? or is that something else... ? sorry... I'm VERY new to using anything other than dirt and water *giggle

Regular lime is calcium carbonate, CaCO3. There are other versions, including dolomitic lime (calcium magnesium carbonate) or hydrated lime (calcium hydroxide). All will raise the pH. This is necessary in some cases because the peat and pine bark in the mixes above is fairly acidic, with pH readings as low as the 4 range. Most peat-based commercial mixes have some sort of lime to neutralize the acidity of the peat.

I use dolomitic lime. My reading leads me to conclude that it is superior for two reasons. First, it contains the magnesium which is sometime deficient in container mixes. Second, it acts more slowly and gradually than, for example, hydrated lime. I adjust the amount of dolomitic lime depending upon the pH requirements of the plant and upon the other ingredients of the mix. If I'm using coconut husk chips instead of pine bark fines, I use less dolomite, because the CHC is closer to neutral pH than the pine bark. If I needed a really acidic mix, like for a Miracle Fruit tree, then I could use pine bark fines and peat and leave out the lime entirely. (I don't have a Miracle Fruit tree yet, but that's my plan!)

I'm glad this thread got bumped. As a supplement, I would like to link the following: http://www.agf.gov.bc.ca/ornamentals/floriculture/aeration.pdf#search=%22total%20porosity%20container%20soil%22 There are nice charts of different media, a method for determining total and aeration porosity, and other useful information.

SB

I saw Happy's note on the other thread and I would add the following. I use essentially the same recipe that Al gives above, with minor modifications. If I have a plant that is a water hog, I use coconut husk chips (CHC) instead of the pine bark fines. The CHC holds more water. Here is a link I wrote on the preparation of CHC: http://davesgarden.com/forums/t/607678/ Since I started that thread, I have started adding 1 part perlite to my mixes. So essentially it's 3-4 parts CHC, 1 part peat, 1 part perlite, plus the additives. CHC is supposed to break down more slowly that pine bark as well.

Oops, I see that the lime question was (at least partly) answered by Tapla above. Sorry Al. ;-)

excellent info. thx Al!

Just stopping by to say thank you for such a bounty of information!

:-)

Fernanda

I don't understand everything, but thanks for the obviously very well-researched information!

David

Here you go Riverland..its a long post but please read it!!!The results are fantastic!!!Made a believer outta my plants!!!

My thanks to Demstratt for telling me about this thread,and to Al for starting it.I haven't had time yet to read all the info here,but sure will be using some of the suggestions here in my containers from now on.

Wow . What great information Tapla and Stressbaby has shared with us. Thank you both for sharing your knowledge with us.
I read somewhere were basket lined with coconut husk can increase salt bulid in soil? If this true, wouldn't it be true with coconut husk in soil?
TIA Patti

Patti, coconut husk chips often contain a considerable amount of salt...not surprising given the distribution of the coconut! For this reason it is necessary to rinse the chips prior to use. I soak and rinse the chips at least 3 times. On the final rinse I add Epsom salts, magnesium sulfate. The magnesium serves to displace other undesirable positively charged ions, a process called "cation exchange." Without this step, magnesium deficiency can occur, I have experienced this with some citrus. Some people also add calcium nitrate, but this compound is not as readily available and I have had no difficulty using the Epsom salts alone.

I am not aware of anything that would suggest that CHC, once rinsed properly, contributes to more salt buildup than any other growing medium. I hope that answers your question. This is a Jaboticaba growing quite happily in CHC.

Stressbaby,
Thank you for taking the time to explain this all to me. I appreciate the education. We are never to old to learn.
Thanks,
Patti
PS: Beautiful plant you have there too. :O) Do you use wicks Stressbaby?

This message was edited Jan 7, 2007 9:47 AM

Rose, I will only rarely use a wick. The last time I used a wick was a year ago when I got a citrus tree just before going on vacation and I didn't have time to repot. I didn't trust the person watering the greenhouse not to overwater the tree, so I put a wick in and the tree did great.

The perched water table in a CHC medium is negligible, nearly zero.

Thanks Tapla and Stressbaby. I have learned a lot of valuable information today.
Thanks again,
Patti

This message was edited Feb 6, 2007 7:15 AM

Thanks, Al and all who posted, especially Debi who sent me the link. I needed this information to be more successful with container planting. I will now print it out and use it.

Al: My DH made two large wooden "tomato boxes" and I'm curious if a length of nylon stocking placed from the top to the bottom hole (there are many holes) would be beneficial right from the first stage of planting. Thanks again.

Hi, Pirl
If you're asking if it could be helpful as a wick - the answer is "yes", it could be. It's not necessary that the wick extends all the way to the top, only into any area of soil that contains perched water. For the wick to be useful, it should hang below the container bottom or be in contact with soil or a surface that will drain excess water away from the wick (as in an inclined surface). The number of holes in the bottom of a container makes nearly no difference where drainage is the issue - 1 hole or a 100 makes no appreciable difference so long as the 1 hole allows water to drain (unclogged).

A wick might be helpful in the early stages of the immature planting before roots have colonized the container to help remove excess water from soil. Roots need an O2-rich environment to remain vital. Since O2 disperses about 10,000 faster in air than in water, it is necessary to remove water from the lower reaches of the container for roots to function properly. When the planting matures and uses water at a rate that requires you to water daily, then you can remove the wick, which will then have the effect of extending intervals between waterings.

I hope I understood your question and answered it to your satisfaction. If not, please ask again with a little more detail.

Al

As for the drainage holes remaining unclogged - would you consider a coffee filter as a good or bad use? Thanks again, Al.

Ohh - it will probably work long enough before it breaks down, but I prefer Fiberglas window screen (or a plastic mesh you can buy at hobby shops for needlepoint application) - it's effective, reusable if you prefer, and very inexpensive. I'll send you some if you like, or you can buy a roll at any home improvement store for a couple of bucks. I've never had a clogging issue with the soils I use.

Al

Great. We already have a roll of it in the garage. Thanks so much for all of your help.

REPORT:

I repotted a bunch of young plants and the wick and is very effective. I actually used old mop strings. I'm sold, and will use it in all potting henceforth!

Rj

I also will follow Als(tapla) soil mixes!!!!Thanks for bringing this back up.............

RJ - great idea!

I just want to personally thank Demi,for telling me about this thread.I have learned so much just reading all of your posts here.Thanks again,to Demi.and tapla for all of his information!!

Hear hear. I second the motion...
I don't know where I'd be without the folks here.
Rj

Tapla: What is micronutrient powder??? Can you please name some brands? Do you mean something like Superthrive (except that is a liquid)?

or would that be, the sulpher, blood meal, bone meal etc?

There are a few supplements available that are specifically compounded to deliver micro-nutrients. Usually, in the powdered or granular micro-nutrient mixes you'll find the macro-nutrients (majors) magnesium, calcium and sulfur, along with the micro-nutrients (minors) iron, boron, zinc, copper, manganese, molybdenum, chlorine, cobalt, and nickel.

Two reliable and commercially available powdered chemical mixes are Micromax (insoluble) and STEM (soluble). Earth Juice and fish/seaweed emulsions are a couple of reasonable organic sources for some of the minor elements too.

I have done some experimentation (keeping loose controls in place) with Superthrive, and have found it useful for stimulating the growth of new roots on cuttings and recent repots only, and have perceived no value in it as a tonic or general plant stimulant. I have the description/results of what I saw in the experiments if any are interested in seeing it posted.

Al

I'm glad Happy asked that question!!I was wondering about that myself!I know I will be trying some wicks in my containers this spring!!

Al, I would be interested in your Superthrive results.

Hi, Bob. Good to see you!

Superthrive or Superjive

The question of the value of Superthrive as a miracle tonic for plants is often bandied about in horticultural circles. Several years ago, after reading claims that range from “I put it on and my plant, which had never bloomed, and it was in full bloom the next day” to “It was dead - I put Superthrive on it and the next day it was alive and beautiful, growing better than it ever had before”, I decided to find out for myself. If you look for information on the net, you’ll find the manufacturer’s claims and anecdotal observations, so in want of anything that resembles a control. Though my experiments were far from scientific, I tried to keep some loose controls in place so that I could make a fair judgment of its value, based my own observations. Here is what I did, what I found, and the conclusions I made about my use of Superthrive.

On four separate occasions, I took multiple cuttings. In each case the group of cuttings were taken from the same plant. The plant materials I used were: Ficus benjamina, (a tropical weeping fig) Luna apiculata (Peruvian myrtle), Chaenorrhinum minus (a dwarf snapdragon), and an unknown variety of Coleus. In each instance, I prepared cuttings from the same plant and inserted them in a very fast, sterile soil. Half of the cuttings were soaked in a Superthrive solution of approximately 1/2 tsp per gallon of water. The other half of the cuttings were watered in with water. In subsequent waterings, I would water the “Superthrive batch” of cuttings with a solution of 10 drops per gallon and the others with water. The same fertilizer regimen was followed on both groups of cuttings. In all four instances, the cuttings that I used Superthrive on rooted first. For this reason, it follows that they would naturally exhibit better development, though I could see no difference in vitality, once rooted. I can also say that a slightly higher percentage f cuttings rooted that were treated to the Superthrive treatment. I suspect that is directly related to the effects of the auxin in Superthrive hastening root initiation before potential vascular connections were destroyed by rot causing organisms.

In particular, something I looked for because of my affinity for compact branching in plants was branch (stem) extension. Though the cuttings treated with Superthrive rooted sooner, they exhibited the same amount of branch extension. In other words, internode length was approximately equal.

As a second part to each of my “experiments”, I divided the group of cuttings that had not been treated with Superthrive into two groups. One of the groups remained on the water only program, while the other group was treated to a 10 drop per gallon solution of Superthrive. Again, the fertilizer regimen was the same for both groups. By summer’s end, I could detect no difference in bio-mass or vitality between the two groups of plants.

Since I replicated the above in four different trials, using four different plant materials, I’m confident in drawing some conclusions as they apply to me and my growing habits or abilities. First, based on my observations, I have concluded that Superthrive holds value for me as a rooting aid, or stimulant if you prefer. I regularly soak the soil, usually overnight, of my newly root-pruned and usually bare-rooted repots in a solution of 1/2 tsp Superthrive per gallon of water. Second, and also based on my observations, I don’t bother with its use at any time other than at repotting. No evidence was accumulated through the 4 trials to convince me that Superthrive was of any value as a “tonic” for plants with roots that were beyond the initiation or recovery stage.

The first ingredient listed as beneficial on the Superthrive label is vitamin B-1 (or thiamine). Growing plants are able to synthesize their own vitamin B-1 as do many of the fungi and bacteria having relationships with plant roots, so it's extremely doubtful that vitamin B-1 could be deficient in soils or that a growing plant could exhibit a vitamin B-1 deficiency.

Some will note that I used more of the product than suggested on the container. I wanted to see if any unwanted effects surfaced as well as trying to be sure there was ample opportunity for clear delineation between the groups. I suspect that if a more dilute solution was used, the difference between groups would have been less clear.

It might be worth noting that since the product contains the growth regulator (hormone) auxin, its overuse can cause defoliation, at least in dicots. The broad-leaf weed killer Weed-B-Gone and the infamous Agent Orange, a defoliant that saw widespread use in Viet Nam, are little more than synthetic auxin.

Al Fassezke

Al,

Great information, thanks! I'm going to make great use of it, but I have a question for you that is specific to my region. It's hot, hot, hot here in the summer, and dry, dry, dry. I can see a pot with that soil mix drying out very quickly (in a day) and being difficult to rewet. What about substituting vermiculite for the peat?

Lynn

Hi Lynn ;o)
You may be surprised to learn that sphagnum peat holds about 90% water by volume at saturation and gives it up over a fairly even curve until it becomes so tightly held in the media it is essentially unavailable to plants at about 30 kPa when it still retains about 30% water. #2 and #3 vermiculite both hold about 71-72% water at saturation and give it up over similar curves until they reach about 30 kPa with about 28% remaining as unavailable to plants.

What this means is that when peat and vermiculite reach about 30% water content, they both hold water so tightly that plants cannot extract it from the media. However, peat initially holds about 28-30% more water by volume than vermiculite, so it is actually a better choice than vermiculite insofar as water retention is concerned, especially since their availability curves are similar.

You may wish to consider adding some polymer or starch granules specifically packaged to sell as a moisture retention aid, or include some rock wool in your soils. Rock wool holds about 90% water by volume at saturation and gives it up over a steep curve, making almost all water held available at tensions as low as 5 kPa. It also does not become hydrophobic when it dries down like peat. I think I would retain the peat in the mix and replace a portion of the perlite with rock wool.

Al

Where do you buy rockwool in a form suitable for use in amending soil?

Wow! Thanks Al :o)