can I 're-use' potting soil?

Tracey3345(Hamptons, NY)May 13, 2005

Last summer I purchased a cottage that came with many potted plants on the deck. In preparing for winter, I ripped out most of the plants as the previous owner had instructed and stored the pot & soil in a small shed. For others, I left the plants in place (mostly trailing ivy that I'd hoped would survive) and covered it with a tarp for the winter (the ivy didn't make it). The result is that I have many pots filled only with "old" soil. Is this soil usable, or must I buy new bags of potting soil? Thanks in advance!

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PVick

You'll probably get differing views in response to your question, but personally, I do re-use potting soil (unless the pot previously held a diseased plant of some kind, then I chuck it). I remove maybe the top inch or two of soil, and rake through the remaining, removing any big clumps of old roots, etc. Then I mix in some fresh potting mix, toss it all together, plant and finish off with fresh soil.

Has worked fine, so far .........

PV

    Bookmark   May 13, 2005 at 8:25PM
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tapla (mid-MI z5b-6a)

Bulbs & pansies.

Though I don't reuse mine, except as I'll explain, I won't quibble with those who do.

Even though I use pine bark as the primary component of my soils, I don't use it in subsequent years except to the extent that I'll retain several containers and plant bulbs in the old soil in the fall. I leave the containers in an unheated garage where they are very dry and bulbs are able to stratify. I also save a few containers with old soil to plant pansies come spring. After the bulbs fade & the heat starts to stress the pansies, I empty the containers & start fresh.

My reasoning: I make aeration my #1 priority in all my soils. Even with pine bark, the decomposition is greatly accelerated in the second year of soil usage. With peat soils, the soil breakdown is even faster. I won't risk a mediocre container display because of structureless soil. I want everything to look good with a minimum of effort, so I don't want to stand & scratch my head wondering if I should water or wait another day. I can water my soils freely without worry of soggy soil, & that's just what I happen to prefer to grow in. Your choice may be different, or the number of containers you grow in may allow you more time per container. ;o)

I buy soil components in big quantities, so it's very inexpensive to replace the soil, even in up to 30 garden containers each year, plus the potted flowers & trees.

Good luck & good growing, whatever you decide.

Al

    Bookmark   May 13, 2005 at 10:02PM
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gitanjali(z6 ID)

Hi,

I had quite a number of plants die due to powdery mildew last year. I think I need to change the potting soil (if there is no other way of salvaging the potting soil). Please would you share your source of inexpensive potting soil? Because the only place I have bought from so far is Home Depot. I usually get the Miracle Grow Potting Mix and it can get quite expensive replacing soil in most of the pots. I could use a recommendation on a brand of potting mix too. Please help! I am new to gardening. Just joined this forum and have already learned a lot.

Thanks!

Gitanjali.

    Bookmark   May 17, 2005 at 2:24AM
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tapla (mid-MI z5b-6a)

From a recent thread I atarted:

My Soil

I'll give two recipes. I usually make big batches.

3 parts pine bark fines
1 part sphagnum peat (not reed or sedge peat)
1-2 parts perlite
garden lime
controlled release fertilizer
micro-nutrient powder (substitute: small amount of good, composted manure

Big batch:

3 cu ft pine bark fines (1 big bag)
5 gallons peat
5 gallons perlite
1 cup lime (you can add more to small portion if needed)
2 cups CRF
1/2 cup micro-nutrient powder or 1 gal composted manure

Small batch:

3 gallons pine bark
1/2 gallon peat
1/2 gallon perlite
handful lime (careful)
1/4 cup CRF
1 tsp micro-nutrient powder or a dash of manure ;o)

I have seen advice that some highly organic soils are productive for up to 5 years. I disagree. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will far outlast any peat based soil) you should only expect a maximum of three years life before a repot is in order. Usually perennials, including trees (they're perennials too, you know ;o)) should be repotted more frequently to insure vigor closer to genetic potential. If a soil is desired that will retain structure for long periods, we need to look to inorganic amendments. Some examples are crushed granite, pea stone, coarse sand (no smaller than BB size in containers, please), Haydite, lava rock, Turface or Schultz soil conditioner.

    Bookmark   May 17, 2005 at 7:14AM
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gitanjali(z6 ID)

Thanks! I will try out a small batch first ( though eventually I will need to change the soil in almost all my containers). Thanks a ton!

Gitanjali.

    Bookmark   May 17, 2005 at 7:05PM
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breezyb(z6/7VA)

Unless I've had a plant die from some hideous disease, I definitely re-use my container potting soil.

That said, I do dump it out & remix it with some fresh compost before replanting.

    Bookmark   May 17, 2005 at 8:09PM
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ImaHockeyMom(SW Mich--Zone 5)

In my area, I can get a 40# bag of potting soil at Wal-Mart for $1.50. I don't know about its "quality" or anything compared to the name brands, as this is my first year to do any real gardening, but it was better than the stuff I got at Frank's last year (which had a bunch of CLAY in it -- who puts hunks of clay in potting soil? No wonder Frank's went out of business!)

The Soil Snobs are probably rolling their eyes at me, but that's their problem. It was "cheap and easy" or "nothing at all" for me this year, so Wally World got my money.

    Bookmark   May 25, 2005 at 1:03PM
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mea2214(z5 Chicago)

I'm new here and just read that long thread on container drainage and now have some ideas for improvement. I always recycle soil. There is no way I could possibly mix new soil for my entire container garden each spring and expand it. This year I have already bought over 130 40 lb. bags of dirt for the installation of new planters! And that was a lot of work. My big wildflower containers which are 8'x2'x12" deep hadn't been changed in 4 years. In the fall I amend the old soil with compost, get rid of the old plants and rootballs, loosen it up, and plant the seed. For containers that don't have perennials, in the spring I empty them into my dirt mixer (which is one of those large Rubbermaid storage things I found in the alley a bunch of years ago), add some compost and new soil and perlite, mix it up and it's ready to go into a new planter.

So far I found Menards to have pretty decent dirt and I've tried dirt from all the places around here. I mix one bag of their cheap topsoil (which is pretty good with very few clayballs) with one bag of potting mix with 1/2 bag of mushroom compost and a coffee can of perlite. It may not be the best soil but it works. I grow wildflowers, veggies, herbs, and only a couple of annuals.

Last fall I had a big ficus tree and a 2 year old rosemary that I grew from a seedling die on me after bringing it inside last fall. I now think my soil mixture and lack of drainage had something to do with that. These discussions here have been very helpful and I'm going to experiment using wicks and maybe there are other things I can add to amend the soil to make it better.

    Bookmark   June 1, 2005 at 2:49AM
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dawgie(z7NC)

I sometimes reuse potting soil after I've removed the roots and other debris, particularly for easy-to-grow plants such as impatiens. I also make a habit of reusing the soil in pots to start new planting beds or add to existing ones. Eg, I have tried to grow plants around our storage shed for a while but the soil was heavy clay and most plants didn't grow well there. Early this spring, I dumped a bunch of old pots in that bed, raising the soil level about 4-6 inches. Then I planted some new hostas in the bed and they are thriving.

    Bookmark   June 6, 2005 at 11:52AM
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LaurelLily(9a Houston, TX)

I dump my used potting soil into the compost tumbler, which gets nice and hot, so that anything bad in the soil is killed before it's mixed in with more soil for planting.

    Bookmark   June 8, 2005 at 2:51PM
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mrzek(z5 IA)

I definitely re-use my soil, but as others said, I buy some new and mix it with the old stuff. Be careful buying cheap "potting soil." I did it this year and found some interesting and illegal plants sprouting that I had not planted.

    Bookmark   June 10, 2005 at 9:20PM
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Eliza_ann_ca(zone 6 ont ca)

I usually dump all the soil from last years containers into a wheelbarrow and mix in equal parts of new potting soil.Been doing this for years,and so far have not had a problem.

Eliza Ann

    Bookmark   June 14, 2005 at 8:28PM
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bassketcher

You can sterlize used potting soil by heating it. I use boiling water or some times nuke it. i am working on getting a microwave just for gardening.
The problem I have with the original poster question is she does not know what may or may not have happened because the potting soil was some one elses first.
My brother bought a house with a nice green house in it. All of the soil in the green house was full of cut worms. I would recomend sterilizing used soil of unknow origin and reamending it with good compost.

    Bookmark   June 15, 2005 at 9:02PM
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ljrmiller(z7 NV)

I pitch my old potting soil unless the containers are too large to make it manageable. Then I just top-dress with more potting soil as needed. But actually I don't throw the potting soil away--where I "pitch" it is into my compost heap. Every Fall, before the leaves start really coming down, I harvest the compost from the bottom of my bins and throw it all over the garden.

I have a LOT of pots to fill every year--next year I'm going to just order in a full pallet of my preferred potting mix and be done with it.

    Bookmark   June 18, 2005 at 4:54PM
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loomis(Z6a Western MA)

I, too, recycle my potting soil. I add lots of good compost, a little bone meal and some dried blood. I also add additional water absorbing crystals if needed. Then I add the plants & top it off when fresh potting soil.

So far I've had no problems.

    Bookmark   June 23, 2005 at 11:56PM
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