Greetings Forum Members. I am new to gardening and this year planted 180 plants from seed, all to grow in containers. I've had to bring in a substantial amount of potting mix in 3 cubic yard bags ( a muscle building experience). The mix is good quality with fertilizer. I've added a substance to help the mix retain water (small dry cyrstal-like additive). My question is, can I re-use this soil next year if I keep it carefully over the winter in a clean container. Thanks for your thoughts.
Can potting mix be re-used?
First, I want to understand your question a little better...are you wanting to re-use soil that you already grew plants in this year? Or do mean that you have leftover soil that you want to hold over until next year? If it's leftover soil that was never used, then it should be OK to use. However, if you're wanting to re-use soil that you already grew plants in, that's a bit riskier. It's not generally recommended to re-use potting mix--there's always a chance that there would be some fungus/bacteria that got in the soil this year that could cause problems for whatever you plant in it next year. If you are starting seeds in it I definitely wouldn't recommend re-using it, you're asking for fungal problems. If you're using it for larger plants, you may be OK as long as the plants you had in it this year didn't have any diseases, if they did then I would definitely throw it out and start again, but if they were healthy then you might have success with it but you are taking more chances than you would be if you bought fresh. The one thing you would need to do though is add more fertilizer, the plants that you had in there this year probably used up much of whatever came with the soil.
I've been growing in containers for a while (this year I have over 70 plants in self-watering containers). Just out of laziness I'd dump the soil in a part of the yard where we wanted to build up a spot, but last year I didn't want to go to the time and expense so I decided to reuse the potting soil (many others reuse it too). I dumped the old soil in a pile to over winter. In the spring I hit clumps with a shovel to break them up and I removed the clump of roots that hadn't composted away.
To 3 parts soil I added about 1 part of new potting soil and mixed it in (I did this in wheel barrel amounts because I had a lot to do and I'm not that strong). I filled the container to about 4/5 full and topped it off with compost. I added greensand and epsom salt to the planting hole and and placed a circular strip of osmocote slow release fert. around, but not touching, the plant stem. On top of this I mulched with grass clippings (chemical free) which dries and looks a lot like straw (neat and keeps the soil from splashing up).
Everything is growing like gangbusters this year. I can't speak for the whole season, but I think my garden is healthier than last year at this point. We've had a lot of rain which could have exacerbated any fungal problems, but to date I have none.
Thank you so much for the detailed information it is very helpful. I'm thinking of next years possibilities. I use sterile seed starter first and then potting mix when I move up to the 3" pots, I will purchase new mix for those steps. I was hoping to re-use the potting mix to fill the containers once I'm ready to move the new plants out. Perhaps I can have some sort of mix delivered in bulk. I will carefully watch my plants for disease and fungus and dispose of that dirt completely. I will be sure to add fertilizer as well. Thanks again.
i have been growing some tomato plants in containers for years and reuse the potting mix several times. in fact, if you ever heard about earth boxes (eb's) they say you can reuse the mix 4 times.
I have about 30-40 containers on my deck and I never change out the soil..I plant summer flowers in the late spring and pansies in Oct. All I do is rip out the old rootballs, turn the soil some, take out some soil to make room for the new plants, add some slow release fert and plant the new flowers and mulch on top. I don;t even know how long the soil has been in the containers....maybe 6 years?? maybe longer for some. The soil that I take out to make room for the new plants I always put in a new container that I have just bought.
As long as you are adding a fert that is complete ( all the micro nutrients as well as NPK ) and the soil hasn't had a fungus in it, the plants should do fine. Here are some of the containers-how they look right now
here are some more
I agree with the reuse outside in the containers as long as there was no indication of a problem. My outside containers get a good long freeze as we are zone 3 then I like to dig out the top 1/3 every second year but always topdress with the smatcoat time release granuals.
I use brand new soiless mix for my seeds and early transplants , I have found this causes the least amount of trouble. I have also started my plants in bulk, prick out the seedlings and transplant to the 2 inch pots. That way I'm not wasting space to seeds that don't germinate.
Ann
Thank you all for the great advice as well as the beautiful pictures. I have some ceramic pots that might break in a freeze so I think I will remove the soil and place in a new garbage can for use next year. Another question I have thought of is whether all funguses are visible? Do you just watch the plants themselves for sign of fungus? I have two tomato plants, both with mites. Would those bugs, or others affect the quality of the soil? Thanks again for taking the time to share your thoughts. Deborah
no the mites don't subject the soil per say. What any bug or fert/watering problem can do is put the plant under stress and that can leave the plant vulnerable to a fungus.
No you can't see a fungus without a microscope, but you can see how the plant acts with a fungus and usually if you know how the different fungus affect the plants, then you can 95% tell what fungus it is. Only a lab can tell you with out a doubt.
I guess I should have said that if a plant gets a fungus, then the dirt should be thrown away and the pot sterilized.
I also always use fresh, sterile soiless mix to germinate in and to transplant in for my annual crop.
I try to reuse all of my potting soil each year to hold down the costs since I have so many large container plants. I empty the container into a large Rubbermaid tote and add some Worm Gold castings, some water with a few drops of liquid dish soap to help wet it down, and stir it all up to break up the roots and dead dried stuff. When I repot, I add the mixture, a layer of the water polymers, and some Osmocote. I've never had a problem with fungus or anything. Sometimes I find a lot of earthworms in the old potting mix.
BTW, this year I used MG Potting Soil for some new containers and really liked it, but I found something I really, really like for plants that take a lot of water. It's called Sierra Organics Potting Blend and this stuff is great for heavy water users like caladiums and elephant ears. The 2 cubic foot bag weighs a ton! It's really rich, almost black, and I've had the best results from it for the plants mentioned and ferns. I'm leery of using it for some other plants like petunias, etc. It holds 9 times it's weight in water. Here is additional info on it: http://www.sierraorganics.com/pottingblendback.htm
This message was edited Jul 11, 2006 3:21 PM
Thanks so much for the response. I ran out of Schultz mix and started using MG with fertilizer and found it to be much better in quality . I'm intrigued by your formula of gold casings and liquid soap - could you describe a little more about what each product is for? When I started the plants in the pots I have I used a plant starter liquid, wet the earth before the transpant covered with remaining dirt and watered with the same product. So far all transplants are holding up very well in their containers. I'm hardening them off in a shady area and will move them to partial sun soon. Thanks again. Take care, Deborah
Deb,
Earthworms are soil's and YOUR FRIENDS! The more you have, the better. They actually aerate the soil, allowing oxygen to get into the soil, through the little pocket they create while they're moving around in there.
The dish detergent is unappealing to a number of soil mites, aphids, and others. Most importantly, it breaks the soil down and keeps it conditioned and soft, so it doesn't get all funky and clay-ey. Jerry Baker, "America's Premier Gardener" uses detergent, beer, ammonia, white karo syrup and liquid fertilizer as a "green Up" tonic for grass, too.
JERRY BAKER'S ALL SEASON "GREEN-UP" TONIC
Feed your yard every three weeks, in the morning, during the growing season with my All Season "Green-Up" Tonic:
1 can of Beer
1 cup of Ammonia
1 cup of Shampoo
1 cup of Liquid Lawn Food, and
1 cup of Molasses or Corn Syrup
Mix and apply to everything in your yard with your 20 gallon hose-end sprayer to the point of runoff.
Gymgirl pretty much covered it. I use the dishwashing liquid to aid in wetting the soil. I put a few drops in a gallon container, shake it up, and then add it to the used potting soil. It makes the water wetter. You can buy products specificially for this purpose like Soil Wet, but it's expensive and doesn't do a better job. The worm castings are a natural fertilizer that enhances the soil. I buy big bags of it in the spring when it's on sale. I like Worm Gold Plus because it has kelp and minerals added.
Here's an added tip: If you buy a bag of potting soil that is dried out, it is hard to rewet out of the bag. Just open the bag, take a quart of water and add a few drops of dish detergent, and pour into your 2 cubic foot bag of soil. Close it and let it sit in the sun for a day. Viola.....fresh moist potting soil.
This message was edited Jul 11, 2006 3:22 PM
I dump pots of old soil into a big cow mineral tub with intentions of tilling it into a bed or adding it to the compost. Had too many callisia fragrans plants and threw them in temporarily. Now, they are all rooted and growing? They didn't mind the discarded dirt...
edited for how many ways I can spell thru through threw hmmmm.
This message was edited Jul 11, 2006 9:34 PM
wow...don't we differ here! i must certainly change each and every pot's soil annually.
since i push each and every container to max. by continuous feedings through-out our short growing season it's extremely hard on the soil taking and removing all the nutrients that it has. by season's end all nutrients are completely drained out of the soil. i once tried to reuse some of the soil and what a problem it was, resulting in inferior grown.
i will however, use some of the previous years soil to fill the bottle of the extremely large pots that use pounds and pounds of soil.
even reconditioning the soil has not been successful when pushing the plants so hard.
tobee, if you add a good slow release fert, that is going to pretty much cover all your micro and macro nutrients. With the sterlile soiless mix, there really isn't any nutrients in there to speak of to start with-its all in the fert!
tigerlily...mine is mixed by me, i don't buy packaged soils...so there are nutrients in the soil. we have black dirt farms here and i use a highly organic soil base (base begins at no less than 7% organic, which is just a taste high) and then add. i'm insistent in keeping my ph neutral (actually i keep my entire person property neutral ), since most of what i use is adaptable to a "normal" range. it is usually mixed by feb when i'm working 24/7 in the greenhouse preparing for springfest for the county, i usually mix approx or at least 1000 pounds and it's ready for use in may. time release will not help the soil i use to rejuvenate itself. however, it doesn't go to waste, it goes onto one of the compose piles, or used at the very bottom of large pots. i do indeed use time release during growing season. since the type i use is set off by heat, i use it every one to two weeks. when i teach container gardening, i always stress to begin with clean and unused soil for the best results, i don't like to make it more complicated for those just learning. that way they don't have to continuously test, or guess...it's enough to drive anyone crazy!
we have come across those that go nuts with their ph or testing their soils to make sure their micro and macro nutrients are within "normal" ranges for whatever they are growing. they fair no better than those using fresh prepared, potting or garden soils and then perhaps add the micros or macros as needed based on their growing results. however, i have seen quite negative results when using old soil.
i do suppose if you only have a very few pots and want to test and go nuts that may be ok...buy yikes and a half...certainly not for people who grow and plant like us. shoot tiger...i'd still be mixing and hauling!!!!! LOL!
edited for typo's as usual!
This message was edited Jul 12, 2006 1:46 PM
P.S.
Use REGULAR detergent -- not anti-bacterial! According to Jerry Baker, It makes a difference, although he didn't explain how.
tobee - I still think you could reuse your soil by adding a few natural ingredients, but in looking at your pictures, I'd have to say that whatever you're doing, you're doing it right. Those plants are fantastic. I wish my container plants looked half as good. Great job!
Gosh Tobee, I just think for annuals in containers that its fine to reuse the soil. Esp for annuals that are so fast growing and need so little. I just use a slow release when I plant and it keeps releasing all summer-its a 5 month release, so I can add more when I plant the pansies. What kind of slow release do you use that it is gone in 2 weeks? Have never heard of a granular slow release to shoot its load that fast.Whats the brand name and what are the numbers?
I don't even hardly turn the soil thats in the container when I pull out the old plants, though I do try to leave the roots-but not a big issue. Then I just add the fert and plant and mulch-easy as pie. I also like the soiless mix because it drains so well, and if we get a cloudy wet week, I still like the medium to be on the dryer side-esp in containers
For my crops, when I start seeds or transplant, I always use fresh soilless mix, but again I am going for something that drains the fastest. I like to grow on the dry side.
tiger, i'm certain is just fine that you reuse your soil. especially, since you get the good results that you do. it's that i know i do not get the same results when i do. i just prefer not to take any chances.
since you and i are both in business and know that sometimes people may judge our work by what they see...i just made sure i can count on the having the best results possible. our marketing consists of many of the photo's taken of my personal containers, since many of next years offerings are experiments that i do at my personal residence, and if successful used for examples in aug. for the following year. most of our orders are taken in the fall for the upcoming spring based on the grown and style seen in the pictures. people that buy from me want the exact results. (you landscape more than i, i'm a plantscaper, container and bed designs...not landscaper...although i have a huge landscaping job next spring...couldn't pass it up, and i think you should come up and help me with it!).
the time release i use is not retail market available....N-20 P2O5-7 K2 O -14. however, i always recommend to use osmocote which i think is 16 6 13.....close enough. since what i use is heat released you can observe if you place some on the top of a pot in 90 degree weather, by week's end most have been released. of course when you plant some in the dirt itself, it will take longer since the dirt's temperature is lower than that of the surface, yet of course warmer than used directly in ground soil. now we did an "official" study about soil conditions vs fertilizing and i did post it somewhere, sometime. but here's how it went:
using the exact same cultivar of plant, 2 small plots were utilized. plot 1 used the past years previously used soil obtained from numerous containers laying about the campus, which was amended for "perfect" soil and ph conditions best suited for this cultivar. plot 2 was left in it's orginal condition, which was a hard clay soil, it was impossible to use a shovel on this plot, only a pick was able to loosen the clay. each plot had the same size plant placed in it. with plot 1 absolutely NO fertilizer was used. the second plot however, the time fertilizer i listed above was applied weekly. photo's were taken on a weekly basic to calculate both growth rate and overhaul health of the plants. bi-weekly testing of plot 1 were assessed and nutrients were added when needed. plot 2 was never tested and no nutrients added whatsoever during the study. by the end of the 13 week study, the plant in plot 2 had outgrowth the plant in plot 1 by over 70%. that was a substantial finding. the conclusion was that using proper fertilizer was far more important and effective than ph and chemically perfect measured and maintained soil conditions.
in taking the experiment to the next level and using absolute "perfect" new rich soil and adding the same fertilizer, wow....is all i can say.
view the picture below as a large container. new fresh soil is brought in annually, feeding is once a week. keeping in mind, our growing season is based solely on a 12 week time period, results are substantial growth and color. now of course remember, temperatures and other factors are still implied as having a direct impact on the results.
so i think the conclusion is basically, what may work best for one, may not necessary work best for others. it's that what makes gardening such a extraordinary fun challenge
oh! forgot..... and when starting seeds/cuttings i use either a sterile mix or perlite/vermiculite.:)
How it looks from my perspective: If the decision to reuse container soils is an economic one, who can disagree with the decision? If you aren't concerned about expense and are willing to go to some minimal extra effort to build a good soil, that is what I would elect to do.
Here's why: Container gardeners need to direct primary focus to insuring that the soil they are using will remain able to provide adequate air to roots for the expected life of the planting. Along with the ability of the soil to hold ample air, comes good gas exchange and drainage for rootage. All the other major cultural variables affecting growth are easily manipulated. Water, nutrients, sunlight, and to some degree, temperature can all be controlled easily. Aeration cannot and its consideration is as important as water and light to plant vitality.
The breakdown or collapse of soil structure occurs at an exponential rate. If we imagine the usable life of a peat based container soil from a bag, it deteriorates from a reasonably good soil when fresh to unusable after 2 years. It's not unreasonable to expect the soil to lose at least 20-25% of its air holding ability by the end of the first growing season. In the first half of the second growing season, it will lose about another 25% of its air holding ability and in the second half of the second year, near total collapse is likely as the remaining 50% is lost. Though this is an example of an imaginary soil, it is very close to what actually occurs. Another way of saying it is: Even though a soil might be performing acceptably at the end of the first growing season, you should expect a rapidly accelerating collapse in the subsequent year.
So, if you use a soil for 1 year and mix it 50/50 with a fresh, similar soil, 50% of the soil will have totally collapsed by the end of the growing season, and the other 50% will have lost about 25% of its ability to hold air. If a soil is not holding enough air, it's holding too much water. Water and air retention vary inversely in soils and when one increases, the other decreases. When soils hold too much water, you have to hope that the plant will use enough water or that enough water evaporates to prevent root rot issues and even minor cases of over-potting can mean terminal misfortune.
At risk, I speak out often against the use of compost in container soils. It supplies nearly nothing in nutrients and clogs the soil macro-pores container gardeners should covet. Containers are not gardens and much of what works in the garden can cause difficulties in containers.
Additional possible considerations are carry-over of fungal spores, the possibility/probability of insects in various stages (eggs, larvae, etc) and carbonate precipitates from your watering water. A slow soil will also have accumulated fertilizer salts and possibly insecticides that you may have applied and forgotten about last season.
I suggest that container soils be turned into the compost pile or garden and fresh soil used in its place unless monetary considerations prohibit.
Al
al,
i'm in total agreement with you on this point of view, further, i can in no way see any advantage economically, when, in fact, my opinion is that using a depleted soil directly effects the end results negatively. the economics is not solely based on just the cost of the soil and plants, but of one's most valuable time.
Very interesting thread. tobee, I venture a guess that the clay soil was pretty high in nutrients, but no doubt you already knew that. I have clay soil in my gardens, I do not fertilize but I do add organic matter in copius amounts! Container gardens are a different story, I think it's safer to use new soil, BUT find the info about reuse extremely intriguing.
pairiegirl...i KNOW you KNOW that of course that the nutrient storage in clay soils are high, while permeablility is very low. LOL! those of us who have the great pleasure of dealing with it also know it has a sticky feel, high water storage, high compactibility, cold spring temps, and the cherry on top is the ease of tillage ha ha..which is about as tough and heavy as 10 tons of steel!
edited for typo's
This message was edited Jul 14, 2006 4:06 PM
Dear Al,
Thank you and thanks to the other participants in this thread for your time, thoughts and generosity in sharing so much information in answer to my question. In addition to following this thread, I've just read your other thread regarding the "water movement" article. It is great. I have to admit that part of my concern is economic at the moment. So perhaps I will keep this soil for two years, amend it next year and buy new for the third year using your recipe. I fully agree with the poster that noted that there is such a thing as false economy, especially if plants you have taken months to raise will fail as a result of poor soil. I was wondering if you have any thoughts on the crystals that are sold to retain water. So far the pots that I have put them in do seem to be retaining water more than those that don't. I'm using a water meter to check the pots each day before watering. Is it possible that those crystals interfere with soil aeration? Take care and thanks again. Deborah.
Great containers everyone! I to have alot of containers with annuals and tropicals. When I pot everything up, I take out about 1/2 the soil mix from last year and mix in the new soil mix. I have no problems doing it this way. Here are some of my containers.
:) Donna
Another group one.
One more group one.
The sun was shining when I took this picture.
This one didn't turn out to bad.
