I think you should cook it to get rid of the nasties, and then add new peat moss, granulated slow release fertilizer, and anything else you put into your mix.  I only say to cook it, just to get rid of anything bad in there.

Suzi

Thanks Suzi.
 Before cooking it in June hot sun in a clear bag, I should store it outside in a bag  on  a table above ground during the winter to soak  it  in  -30C ottawa deep freeze that should take care of most living things with busted body cells I hope ( I am not a biologist though).

I re-use potting mix all the time, but then I am not a purist. Sometimes I'll just 'fluff it up' and other times I'll add things to it. peat, perlite.. whatever I think it needs. Sometimes even home-made compost. Right now as I am up-potting some of my younger figs, I mix about 1/3 well-aged horse manure (screened), 1/3 used potting mix, and 1/3 whatever, usually compost or decomposed chips. Sometimes a bit of bark. I'm not finicky - but it has to look and feel right to me.

If I get a batch that has a lot of weed seeds, I'll solarize it. I do that by putting the moist soil in a large metal pan, cover it with glass (tempered glass so it won't break), and put it in the sun. After a day or so, I'll stir it and let it go again. That will kill jsut about anything. There are probably other, easier ways to successfully solarize soil.

I do not use planting mix if a plant had some disease - but that isn't common.

Cook it in the oven at 400 degrees for about 15 minutes.  How could this be so mysterious?  If you suspect nasty stuff in there, the oven will kill it.  The rest is pure and can be combined, recycled with whatever you wish!

Suzi

Suzi,

Your method is close to what I recommend to others. 

The way it was taught to me in the University was life is based of water, boil the suckers alive. In that rewording to make more sense is set the oven to 220 F and bake for 30, stir and bake another 30. 

Then again you could do as my friend does and have a big bonfire and some roasted marsh mellows while the bugs burn to death. He places all the soil in a wide trench throws in all sorts of brown materials and some logs. Throw some bourbon on the kindle and set ablaze. Come back the next morning and uses this as soil amendments. Seems to work for him, but I prefer the oven for an hour. 

Thanks for posting this topic.  I was wondering same thing myself.   I've been throwing the used potting soil from cuttings that didn't take and other dead plants into the compost bin.   I have 2 bins, one for stuff that is on it's way to being compost, and another one that is mostly finished compost.  I;ve added it to the finished compost.  I don't think it is probably getting cooked enough in the finished compost because there might not be enough mass.  Then again, the day time temps still get to 100 degrees, so I'm sure it gets pretty hot inside, though not 400 degrees.  

I'm definitely not taking in the soil and putting it in my oven.  Now that is too crazy even for me.  I have a solar oven, but I'm not putting it in there either.   You can easily solarize it by simply putting it into a clear plastic bag in the sun.   I'm not doing either.  I'm just hoping the existing compost mixes with the used potting soil.   To start cuttings, I'm still going to use fresh purchased potting soil, but for repotting, I'm using the finished compost, plus perlite or other stuff depending on what I'm planting.  

I've reused mine too. Mix in perlite and compost to your leftover used potting soil and sometimes horse poop if I have some and VOILA! A new batch of potting soil. I've been doing that for years with no problems.

Since most plants develope some sort of symbiotic relationship with soil bacteria,
it might be better in some ways not to 'cook' it.
The soil may have symbiotic bacteria that is especially adapted to/for/from figs that help them grow.
Why start the process of establishing them all over again?
Unless a plant is obviously infested with something, I reuse mine.

Figfanatic has the right idea. Adding soil to a compst bin is an excellent way to also add soil microbes to get that compost going. If your compost bin is working correctly the soil will heat up and destroy the pathogens. If you cook soil in your kitchen the best way is long and low temps and then look for a good divorce attorney. Also I must admit, that if I am pressed and running low on soil, I will also reuse a portion of old soil and add some amendments appropriate to the mix at hand. No need to waste that good soil.  

I reused mine as well, its coco coir, manure and some times triple mix, I just chop it up and it into a new pot, if I need to add more stuff then I do, but often I don't.

If your plants are growing fine when it is time to repot there shouldn't be a need to cook the mix.  I would just add some compost (or good topsoil), greensand, pelletized lime, and balanced slow release fertilizer to get organic matter and micronutrients back in there and reuse.  If the results of this mix don't feel light enough add some perlite. 

I agree, no need to cook. If you have had problems with a plant and you getting rid of, don't add that one to compost pile, bag it and trash it. That way you know your not adding something that could give you problems down the road. If filling your oven with potting mix, makes you happy, then do it by all means. Whatever way you go you will be fine.


luke

I add composted animal manure, composted vegetable matter and worm castings to all my soil mixes, reused or new.  Just a small amount of each.  You never know what nutrients may be missing from any particular soil.  But too much and you ruin your good drainage.

If you have a bunch of nasties, dead root bits, plant matter etc etc. A good dose of enzymes will eat all bad, rotting stuff and turn that into plant nutrients. It will, in a sense clean the soil. There tons of enzymes for soil amendments, I use pond scum remover from home depot. Beneficial bacteria will also help clean the soil. I would use dolomite lime to raise the ph of used soil.

I add perlite, fully composted compost, and some weak fertilizer.  I recycle potting mix all the time with no problems and I don't even cook it!  LOL

Hey Noss,

Here is what Wikipedia has on greensand, "...The green colour of greensand is due to variable amounts of the mineral glauconite, an iron potassium silicate with very low weathering resistance; as a result, greensand tends to be weak and friable. It is a common ingredient as a source of potassium in organic gardening and farming fertilisers. Greensand glauconite is used as a water softener for its chemical-exchange properties. Greensand coated with manganese oxide (called manganese greensand) is used in well water treatment systems to remove dissolved (reduced) iron and manganese with the addition of an oxidant, usually potassium permanganate, under controlled pH conditions.[12] It is also used as a type of rock for stone walls in areas where greensand is common."

Noses,
Greensand is a natural fertilizer derived from ancient sea deposits. It is a good source of potassium as well as over twenty micro nutrients. It also helps loosen soil making it more friable. I use it a lot in my vegetable garden and orchard.

Thank you all for your input. It was a good discussion and encouraged me to continue recycling the used potting mix with some added amendments/refurbishing.