Return to the Frugal Gardening Forum | Post a Follow-Up

 o
Reusing potting soil

Posted by Growin_Crazy z9/10 FL (My Page) on
Sun, May 25, 03 at 19:14

Does anyone here reuse potting soil? I do, and here's how I do it. I take the old potting soil, put it in a 3 gallon pot, and pour a kettle of boiling water through to kill it, then I mix it half and half with new potting soil. Things grow very well in this, and I've never had any root rot problems from the old soil


Follow-Up Postings:

 o
RE: Reusing potting soil

I do the same thing and also have good results. I've heard of spraying the soil with fungicide, but don't know how well this works. I would think it might not kill every bad thing lurking in the soil.
Barb


 o
RE: Reusing potting soil

yeah, i think the boiling water treatment is enough. this obsession about everything having to be new, shiny, fresh, sterile is nuts! like the sterilize the pot business- jeez, you're putting DIRT in it!


 o
RE: Reusing potting soil

I tried re-using mine this year, I took a large Rubbermaid-type storage container and emptied out all my old pots into that. I mixed in some torn up wet old leaves off the ground and mixed in some bone meal. (I swear by bone meal). I mixed in about 1/2 bag of new potting soil that I already had. I stir it up and let the sun get to it, but put the lid on when it's raining, or at night, etc (doesn't have any drainage. I've used this for all my deck gardening so far........ wish me luck?


 o
RE: Reusing potting soil

Good luck Holly.... I've kind of done similarly most years too. I empty the soil & roots from spent potted plants into a large Rubbermaid tote bin, mix with some compost +/- some new potting soil, and use this for the bulk of some new bigger pots (I seem to add to my collection each year), or before this past year when I made (& am still making) a broad-scale renovation of the soil in all the beds, I would use this for specific areas where I put in a new plant (previously a big, difficult job in the root-ridden, hard clay soil). Some of the bigger pots I just amend part of the soil when I plant them. I haven't been doing the boiling water process in the past, but this year am doing that for the potting soil I got for all my seed starts, whether starting indoors or winter sowing - hadn't thought of doing it for other pots and doubt I will. Am being fussy with washing all my containers really well though... just want to be sure I minimized chances of fungal or whatever diseases for my seedlings. And many of my pots are scrounged from other places, so I'm not sure of whether they previously had diseased plants, or in what environment they were stored.

If I don't want to reuse some soil for planting for some reason, I'll toss it in the compost, a bed or on the lawn. I do have some (previously not used) potting soil that was supposed to be "sterile" from the package, but it has somehow become contaminated. I had put it in a Rubbermaid bin so I could take from that more easily than the bag inside the house.... but didn't get to it for awhile (over the winter) and it got fungus all over & in it. Maybe the container wasn't very clean, or the bag had a hole & conditions somehow were good for the fungus to thrive. I usually try to keep whatever I'm scooping the soil out with clean, to avoid contamination. Haven't gotten around to dealing with this batch of soil.... seems a shame to relegate it to the compost; maybe I'll see what boiling water can do with such a heavy infiltration.


 o
RE: Reusing potting soil

Fungi aren't a sign of contamination, just of ongoing life. They're involved in composting along with bacteria and are present in any soil product you buy that hasn't been sterilized. When compost is dried, they go dormant. When you seal material in a dark, tight container, warming and cooling cycles make water condense inside the lid and drip onto the soil. The fungi at the top will reactivate. Most fungus problems in gardening occur because the conditions they need for growth are present (cool,moist,dark and something to eat). Otherwise, they're present, just not growing. I've read that you shouldn't grow container tomatoes in the same soil from year to year because of viruses they are susceptible to, but for the most part, if you didn't have a "disease" problem the first time you grew plants in some soil, you shouldn't have them when you reuse it.


 o
RE: Reusing potting soil

I just dump the soil from the old pots into the bucket of potting soil, crumble it all together and reuse it. No muss, no fuss, and definitely no sterilizing or fortifying.


 o
RE: Reusing potting soil

When I use old pots that sat around for a while, I wash them in Clorox water.
My Mom used to reuse potting soil by putting it in a deep baking pan and put it in the oven. I don't remember the temp or for how long and she's passed away now, but I remember she used to get it pretty hot. She said that would sanitize it and kill any thing living in it, (bugs,seed growth, etc.) especially if the soil was outside.


 o
RE: Reusing potting soil

Gail, You reminded me of a story that a friend tells about sterilizing potting soil in the oven. She had a big batch of it in a nice flat pan and baked it according to instructions that she had. She was amazed at just how BAD it made the house smell. Hubby came home and they agreed that it was bad enough that they couldn't stand to be in the house for supper so went out to eat leaving the pan of soil on a bench inside the house. When they returned they found that the cat had found and used the virgin earth. Miss Kitty marveled at her wonderful humans thoughtfulness in providing her with a nice unused pan of REAL soil for her convenience.
spiderwoman


 o
RE: Reusing potting soil

I bring my numerous deck pots into the garage for the winter. In spring, many of my "annuals" have wintered over - I dig out the top 2-4" of soil, replace it with new, mix in dehydrated cow manure and voila!


 o
RE: Reusing potting soil

spiderwoman....I used to "cook" mine, but you're right. It smells AWFUL! I don't think it does any better than the boiling water anyway.


 o
RE: Reusing potting soil

i guess i'm just lazy or naive or just plain lucky cause i don't sanitize anything, it's dirt, it's natural....i haven't had a "diseased" plant (or at least i don't think so!!LOL)
i reuse pots, soil sometimes...no problem, i've only RINSED a pot if the outside looked icky....
=)i prefer to let nature do her thang ;)


 o
RE: Reusing potting soil

This is the first year I've decided to reuse soil from my pots.I just put it all in a large old washtub,mixed it about half and half with container mix,added a little miracle grow and bone meal,and used it for all my container plants.So far everything is comming along great,even though we've had a rather cool,rainy May month.Everything seems to be thriving.Hopefully all will be well and I won't have any problems later on.I usually spend quite a bit of money on new soil every year,and this year it was really stretching my budget.Will let you know how everything looks later in the season.


 o
RE: Reusing potting soil

I put the old soil in my veggie garden bed so that it gets tilled in. I swipe all the neighbors discarded hanging baskets and such at the end of the year and do the same. I figure it helps break up a bit the heavy clay soil here and it doesn't go to waste.


 o
RE: Reusing potting soil

The plastic oven roasting bag is a great invention for oven sterilizing potting soil- I only do it for seed starting in small quantities now.
My garden is all containers and i root prune every year, so I developed a recycling program to cut costs- all the soil and root prunings go into a 55 gal plastic drum and I add a few handfuls of worms and set it in a cool shady place and water every few weeks to keep moist. Next season when I root prune I will reuse it with blood and bone meal mixed in. Before use,I spread a few inch layer on some sunny concrete and cover with a black plastic tarp for a few days.


 o
RE: Reusing potting soil

You mean you replace all the soil in your pots every year?? Isn't this the frugal gardening forum? I certainly couldn't afford that, and anyway would rather spend the money on plants! I just remove old root balls (which get composted), fluff up the soil, add composted manure and plant away. I've never had any problems. And my planted pots always look lush and wonderful. For the last 2 years I have also been adding a scoop of slow release fertilizer to each pot and the plants love it.


 o
RE: Reusing potting soil

Same here! I've never replaced soil in my containers, just amended with more compost (same treatment as my beds). Never had any problems.


 o
RE: Reusing potting soil

So now that summer is just about gone, how did everyone's potting and plants do this year?


 o
RE: Reusing potting soil

Good results to report here. I'm one of those who re-uses the pots often without doing anything. I take the old root balls out in the spring (with the dirt they have on them,) 'stir' it up a bit, refill with plants, and replace as much soil as necessary. If the soil really doesn't look good, I will dump it into the new soil mix, incorporate it, and keep going from there. Everything is doing well this year, with some overwatering exceptions due to all the rain we've had (11 inches in Aug.!)


 o
RE: Reusing potting soil

I do exactly what memyselfandi does. Just add more the next year as necessary.
Gayle


 o
RE: Reusing potting soil

Hello,
I'm new at this board, now that the season has come to a end, I'm searching around for info for next spring. Love the site, looks like alot of good information. My question is, what can I do with bags of indoor potting soil? They have been left outside for the summer months. Can I use them next season in my garden? Should I just store them in the shed for the winter. Please help, I dont want to get rid of good bag of soil.

Thanks


 o
RE: Reusing potting soil

  • Posted by mikee2 5 Scotia, NY (My Page) on
    Tue, Nov 18, 03 at 22:14

Hi Springchild - this is the frugal forum - we don't throw out haha! If you have room in your shed, I would store them there. If they are already opened, a few weed seeds may have blown in but no big deal. I never heard of potting soil having a shelf life - you can plant with it next year! If you haven't been over to the Winter Sowing board - jump on over. You may find some use for it this winter :).


 o
RE: Reusing potting soil

Thanks Mikee2, I will store them in my shed. Should I add anything to the soil, before using it. I know that it is indoor soil, which is different than outdoor soil. Should I add peat moss to it or compost?
Thanks


 o
RE: Reusing potting soil

You can add either fertilizer or compost. Fertilizer tends to build up salts in the soil, so compost is a better choice.

Vicki


 o
RE: Reusing potting soil

If you're one of those people who like to "cook" your soil, you can put it in an aluminum roasting pan and cook it on your grill outside. Saves the odor in the house.

(That might be a good way to get a night out! What's for dinner? Stinky potting soil.)

Barbara


 o
RE: Reusing potting soil

I have had luck with leaving used soil outside for the winter, covered. The freezing temperatures takes care of any disease. I reuse everything!!
TrowelGal


 o
RE: Reusing potting soil

  • Posted by mikee2 5 Upstate, NY (My Page) on
    Tue, Mar 9, 04 at 19:45

You can also toss boiling water on the potting soil to kill most weed seeds. It doesn't stink like cooking it does.


 o
RE: Reusing potting soil

I just buy a new 20 kilo bag of potting mix for $3.25
it's cheap enough,and I mix the old mix into new garden beds that I make, or add it on top of existing beds,to condition the soil.
The worms mix it in for me.


 o
RE: Reusing potting soil

Get a big foil roasting pan and sterilize the soil in the bbq grill outside.

Kathy in illinois


 o
RE: Reusing potting soil

If my older soil is clear of roots and weeds I just dry it out and mix it with some new compost and a bit of soil and a touch of coffee grounds. I don't know why... I've always figured 'dirt is dirt'. As long as I take care of my plantings there shouldn't be any problem. Any of my 'crappy' used soil recycles into the flower beds. Jim


 o
RE: Reusing potting soil

"it is indoor soil, which is different than outdoor soil." Love it!! I have a bad case of invasive indoor soil, it multiplies rapidly. You should see my vacuum cleaner bag. I think it likes pets and children.


 o
Just noticed...

Whoa, if you post at midnight, it reads as 0:00.


 o
RE: Reusing potting soil

I've been following this thread for some time with a great deal of interest.
I'd like to used compost for starting seeds, but want it to be sterilized. Also, I want to sift it pretty fine because a lot of the seeds I want to plant are very small.
I was thinking of sifting the amount I needed, then using the microwave to sterilize it.
Has anyone tried this? It seems to me it ought to work and be less hassle than the boiling water or baking in the oven.


 o
RE: Reusing potting soil

I like to combine old (worn out?) dirt from potted plants with compost, stick it in large, black leaf bags (which I re-use and re-use until they fall apart) and stick them out where they will sit and 'bake' in the sun for a couple of weeks...

So far *knock on wood* this has managed to 'bake' all the weed seeds to death and combined with the potted plant dirt, which usually has sand/vermiculite/peat makes a really nice additive to my garden soil....


 o
RE: Reusing potting soil

I microwave used potting soil..... I sift it first through an old deep fry strainer, dampen it slightly, fill a large Corningware or Pyrex container, cover with saran and then microwave for about 5 minutes. I let the soil cool with the saran cover still intact. Lotsa steam to sterilize the soil and no odors....
AdaO


 o
RE: Reusing potting soil

Ada--that's what I did this year. Put some in a paper bag and zapped it for 10 minutes. No fuss, no muss, and no nasty smell.


 o
RE: Reusing potting soil

Really interesting reading here. If, you do it in the oven do you wet the soil? What tempature for the oven. Also for a product like miracle potting soil is it sterilized? Normally I mix and reuse soil with new, but have a batch of gnats and looking for moisquito dunks now. I am rethinking what to do about my soil in future. Thanks


 o
RE: Reusing potting soil

I always re-use my potting soil, have a huge pot bigger than a washtub I put any excess potting soil in & add dried leaves to it when I have them.
It has a lot of earh worms in it, always try to add a few to a new pot to work the soil for me, all my plants are thriving. I wouldn't want to use boiling water or cook the soil & hurt my earth worms!


 o
RE: Reusing potting soil

In the thread several speak about treating the soil, removing the rootball, etc

Do you do this in the fall or the following spring?


 o
RE: Reusing potting soil

if the potting soil has pathogens throw it out. otherwise sterilization is eliminating all the beneficial edaphon.

Healthy soil is alive ~ don't kill it!


 o
And starter mix? Can you reuse that?

My first attempt at seed starting was a total bust, and now I'm left with a tray of starter mix. There are seeds in there (though obviously they're not going to sprout), and I noticed a couple of gnats, but is there ANYTHING useful I can do with it? Thanks.


 o
RE: Reusing potting soil

I'm also wondering about timing - when my tomatoes and peppers are done next month, should I amend the soil then? Should I store it in my shed? Or just leave the plants in there til they give up the ghost and work on the soil next spring? AHH? Sorry to be so dense, but this is new to me. Thanks in advance for your tips. :-)


 o
Reusing potting soil

I've been reading everyones comments on to reuse soil, but do I keep it in the pots in the garage over the winter?
Then in the spring mix it up with new soil and plant as usual? Can I put it all in a big container in the garage and put a lid on/off? I have a liitle green (not much) growth on top of two containers. Do I leave it or take off the top layer? I'm also moving south next year. so I was maybe thinking on taking the soil with me. Or is that a bad Idea? I've got approx. 30 large containers and I'd hate to think of what that would cost to fill them all up again.
Chere


 o
RE: Reusing potting soil

I dump the pot contents into the compost bin at the end of the season to "renew" it. Then in the Spring I go to a couple large chain stores just before they close and buy broken bags of expensive potting mix for $1 a bag. I am still re-using my old potting mix in a way because it all comes out of the compost bin eventually and into some gardening project.


 o
RE: Reusing potting soil

First I dump potting soil from starts that don't make it back into the mix I use for potting soil (shredded peat and the cheapest soil I can find ($1 for top soil HD ... just want something sandy .. I save compost for veggies ... never enough).
If you want to cook soil you can place soil in a flat container, cover with glass or a heavy plastic and place in full sun. This is known as solarization (or solarizing soil)and I do this on a larger scale to kill nematodes when breaking new ground. In short order you will "cook" anything living in the soil. And its FREE!!
Mike


 o
RE: Reusing potting soil

I have a lg deep freeze. It seem that by Feb it's almost ementy. I put the used potting soil from last summer in a lg old soup pot & put it in the freezer for a week. I figure at 30 deg will kill most anything. When I go to plant seeds in it I use Ozmacote fertalizer. I've never had any problems!


 o
RE: Reusing potting soil

I have always reused until this year Most of it was new. I lost a bunch of seedlings to damping off. didn't even think about it mixed the soil back, lost more so I spent the day boiling soil. And my Grandaughter is sick of bleaching pots!


 o
RE: Reusing potting soil

I can't imagine not reusing any kind of soil and I certainly can't imagine baking or broiling it or zapping it...dirt of any kind is precious in the Texas Hill country and I save every smidgeon die ewyaw...but without all the cooking...


 o
RE: Reusing potting soil

Hi there, Last Year I had problems with plants (tomato, pepper, a few peas) in pots on my apartment balcony. They started fine, and produced a little bit. But they were definately affected by some sort of disease. I'm planning to try again this year. I'll wash the pots and stuff with some sort of bleach wash. Can I reuse the soil if I nuke it in the microwave. Or would it be better to throw it out and try new stuff.

Thanks... Mike, Ottawa, Canada, Mar'07


 o
RE: Reusing potting soil

The problem with reusing potting soil isn't diseases, it's drainage. Diseases usually won't be a concern in a well drained, well aerated soil. Drainage can get to be an issue quickly when a potting soil starts to break down. Peat and compost based soils will break down quickly, usually in the first year.

Any frugal gardener should be mixing their own container soil. The commercial stuff is overpriced and of poor quality. Use pine bark as the base, with perlite added for drainage. A small amount of peat can be used to increase water retention. If you use really coarse bark and perlite the soil mix will hold up for more than one year for most applications.

Seed starting is a separate issue--always use a fresh, sterile seed starting mix. Losing seedlings to bad soil is certainly not frugal.

Check the container forum for much more information...

Jason

Here is a link that might be useful: Container Soils


 o
RE: Reusing potting soil

Yuppity. I mixed potting soil myself last year and made mounds and mounds and MOUNDS of it for far less than what it would have cost to buy.

After it's broken down enough that I'm concerned about its drainage in containers, it's still an excellent amendment for my garden beds.

Kristin


 o
RE: Reusing potting soil

Can someone explain the boiling water technique a little more clearly? Is it that you don't use much water and let the soil absorb it or do you need to drain it?


 o
RE: Reusing potting soil

Hopefully we are more enlightened in this decade.


 o
RE: Reusing potting soil

Boiling soil: I have a couple of 5-gallon buckets with lids (ask anywhere that serves pickles regularly to save buckets & lids; it's not uncommon to offer some cash, but not always necessary, especially if you can establish a repoire with the manager) that I use for "boiling soil."

It's as simple as putting the offending soil into the bucket, no drain holes, no prewetting necessary, although if it's really wet maybe let it dry out in the sun for a bit before boiling. I put my full kettle on to boil, and after it whistles, pour the entire contents over the soil. Cover, and leave overnight; the steam will probably do as much of the work as the boiling water itself. If you add too much water, you run the risk of overwetting the soil and causing the components to separate--all the sand ends up on the bottom, and the pretty perlite flakes all on top with the twigs and bark pieces from any compost in the mix. BAD!! Now, you have to 1) let the stuff dry out a bit (in which case new yuckies can get back in, depending on where you do this), and 2) mix the whole thing back up.

As far as using your deep freeze to "sterilize" soil, I've got some news for you: head on over to the wintersowing forum and you will realize in short order that MOST seeds can survive freezing temps, as can most diseases & fungal spores. Bugs won't stand a chance, though, so if you've got some buggy soil, this is a great way to kill them off and then leave them in there--they'll be great addition of protein to your soil.

I generally will do "mini boils" on my wintersowing containers if they're tough enough to take the heat. Otherwise, I have been known to do the boil in the microwave in a glass dish with a plate on top; again, you need to let it sit so the steam can heat through, especially the parts that didn't get directly touched by the boiling water. On that note, I use almost nothing but recylcled soil for my wintersowing, and I wintersow almost everything except for pepper and some bedding flower starts that I want to be bigger before planting out time. For those, I have great success with peat pots unless they don't like acidic soil (peat can also hold too much water and cause damping off, but the capsaicin in peppers prevents this from being a problem), in which case I will use some sterile potting mix--keeping watch for the bargains as have been mentioned above.

By the way, I had some old peat pellets that smelled musty, so I put them into a tub with some water, and nuked the whole thing--they expand very quickly when heated with their water! Beware not to let this concoction boil, however; the peat will break down and your resulting peat ball will have lost half of its contents. Ask me how I learned THAT one!!

Here's a question: anyone reuse peat pots that didn't take? I would think nuking them would make them reusable.


 o
RE: Reusing potting soil

I asked a greenhouse grower why potting soil wasn't generally reused and his answer was that the peat refuses to take up water. Potting soil comes with a "wetting agent" that can degrade or be washed out over time. Therefore it might help to add more of this wetting agent and water it in. Earth Juice sells a product called "Earth Juice Assist".

Another concern is the lime. Potting soil contains dolomite lime which keeps the acidic peat in check as it breaks down. It might be helpful to add some lime to the soil before reuse as well.

Another concern is regarding drainage as the previous poster pointed out. As the peat breaks down it will be more likely to "pack" which can drown roots in their search for air. Adding compost and leaves can exacerbate this problem.

One strange problem I have been running into when reusing potting soil is causing some plants to lose vigor, turn pale yellow and droopy. I do not think it is due to compaction or poor drainage. My best guess is that it is due to nutrient or salt buildup? I am using liquid organic fertilizers but they are very cheap so for all I know they may actually be chemical ferts.

I am growing vegetables so I have been watering with R/O water. Because of this, a flush becomes an expensive and bothersome proposition. Maybe I'll have to flush with "24 hour" tap water and see if that helps the situation.


 o
RE: Reusing potting soil

Just curious. If old peat is such a problem, why is it used in sq ft gardening. Once you have mixed the first batch of "soil' all you need to add going forward is more compost. If you are planting in this old peat year after year, why isn't it causing a problem like you described?


 o
RE: Reusing potting soil

reuse of soil is a good way to garden on a budget. in most casual garden situations you can use the same soil without doing anything more than a fresh water rinse through the soil. do not use boiling water, bleach, or other chemicals that will sterilize the soil and make it dead. even dry soil is actually very much alive with micro-organisms like microrizal fungii and beneficial bacteria. without these things your plants will not grow, the soil you buy contains thousands of these put there by the companies making it (which is why people have to bring their soil back to life by adding purchased soil to it after killing it with boiling water =0 ).

My tips for possible soil reuse problems (container plant methods):

one of the most common problems you will face with reused soil is nutrient salt buildup. this is easily avoided by having proper drainage, as well as flushing your plants with plain water about once a year or season depending on type. (preferably with as little chlorine in the water as possible, it will kill beneficial organisms in the soil)

The other common problem is soil pH balance. I recommend you buy a soil pH test kit about once a year or season and test your soil when you are preparing to reuse it to verify that it is within range for the plant/s you want to grow with it. If the soil is not within it's proper pH range, you can add dry supplements or chemical adjusters to modify the pH to be within acceptable levels.

Another issue you may face is disease. If a plant is lost to root rot or similar soil based disease, you can use the boiling water technique to sterilize the soil. then either add some fresh soil, or you can purchase a packet of microrizal fungii and bacteria from the garden shop to add into the sterilized soil. You should also combine the fungii packet with some dry animal and plant nutrients to provide a sufficient food source to re-colonize your soil with micro organisms.
(note: a healthy compost pile can contain the right bacteria, fungii, and nutrients to re vitalize sterile soil. however there are a lot of common food items that should not be put into a compost pile that is intended to be used in a garden. alos, the compost should not be too "hot" when added. look up composting for more info)

hope this helped, and have fun playing in the dirt =)


 o
RE: Reusing potting soil

I know it's been nearly a year since this thread was last posted on, but I want to thank everyone for the good information contained therein. And particular thanks to DrJonez for pointing out some very good reasons for NOT heat sterilizing or pouring boiling water over soil (namely soil is a living ecosystem, you end up killing as many good things as bad with heat).

I liked the advice about flushing the soil with regular temp water. But I live on the 2nd floor, I don't have easy access to a hose, and I wouldn't want to send tons of water to my downstairs neighbor's (actually, landlord's) patio. I wonder, if you've had a wet spring, will the containers be sufficiently flushed? or almost sufficiently flushed?


 o
RE: Reusing potting soil

Anybody microwave soil for reuse?


 o
RE: Reusing potting soil

we used to dump all the containers out and stir up the soil, add a little new stuff and plant them back up again. but for the past few years we dont even dump out the containers anymore (the big ones) we just stir up all the soil, plant and fertilize. havent had any problems at all, and its so much easier than dumping it all out and mixing up then repotting!

i do like the idea of testing the ph, ive never done that. i will have to do a search on plants salts and their build-up. we get tons of snow and rain so i think the pots get a good soaking and draining anyway. oh - and only rainwater to water them.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Frugal Gardening Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here