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.

Yes, still usable. If you can spread it out on black plastic, so the heat of the sun can get to it; should work out fine. The nasty odor will rapidly go away with exposure.

David - this is written in a conversational tone, even though I disagree with you on a couple of points. First, the reason I don't reuse my potting soil, and I start with a soil that has as its primary fraction, large particles of pine bark, which takes 4-5 times longer than peat to break down, is that I have found it VERY advantageous to keep my focus on aeration. There are actually ways to quantify a good soil and compare it to a lesser soil by examining it's total porosity and air porosity at container capacity. Container capacity is the soils state of water retention after it has been completely saturated and has just stopped draining. You cannot achieve a level of either total porosity OR air porosity at container capacity using broken down particles of peat/compost/coir as the primary fraction of your soil, even with a considerable volume of perlite added. If you are left with nothing but perlite, which doesn't seem like something that would occur as a common scenario in normal cases of soil aging, then we really aren't talking about reusing an old soil; rather, we'd be talking about reusing the old perlite fraction, which is something quite different. So, if you are reusing the old soil as a significant fraction of the current soil, its very likely you're putting yourself at a distinct disadvantage because of the inherent reduction in aeration and probable excess water retention. I'm not pointing out these facts to disparage how you grow, only so we can understand that SAYING a soil drains well (or is well-aerated) doesn't mean it actually does (or is). We KNOW that fine particles hold more water than coarse particles (of the same material) and vine organic particles tend to compact, further reducing aeration and increasing water retention. IF you were to use inexpensive pine bark as the primary fraction of your soil, and add enough of your used soil to arrive at a favorable state of water retention, you would end up with a soil that DOES have favorable total porosity and air porosity at container capacity. If the soil is entirely broken down as you suggest it is, you STILL need to buy something to replace the lost volume, unless you're using compost ..... and then you end up right back where you started - so why not buy inexpensive pine bark instead of another finer ingredient? Something I wrote on another thread about rooting in water: Though roots form readily and often seemingly more quickly on many plants propagated in water, the roots produced are quite different from those produced in a soil-like or highly aerated medium (perlite - screened Turface - calcined DE - seed starting mix, e.g.). Physiologically, you will find these roots to be much more brittle than normal roots due to a much higher percentage of aerenchyma (a tissue with a greater percentage of intercellular air spaces than normal parenchyma). Aerenchyma tissue is filled with airy compartments. It usually forms in already rooted plants as a result of highly selective cell death and dissolution in the root cortex in response to hypoxic conditions in the rhizosphere (root zone). There are 2 types of aerenchymous tissue. One type is formed by cell differentiation and subsequent collapse, and the other type is formed by cell separation without collapse ( as in water-rooted plants). In both cases, the long continuous air spaces allow diffusion of oxygen (and probably ethylene) from shoots to roots that would normally be unavailable to plants with roots growing in hypoxic media. In fresh cuttings placed in water, aerenchymous tissue forms due to the same hypoxic conditions w/o cell death & dissolution. Note too, that under hypoxic (airless - low O2 levels) conditions, ethylene is necessary for aerenchyma to form. This parallels the fact that low oxygen concentrations, as found in water rooting, generally stimulate trees (I'm a tree guy) and other plants to produce ethylene. For a long while it was believed that high levels of ethylene stimulate adventitious root formation, but lots of recent research proves the reverse to be true. Under hypoxic conditions, like submergence in water, ethylene actually slows down adventitious root formation and elongation. If you wish to eventually plant your rooted cuttings in soil, it is probably best not to root them in water because of the frequent difficulty in transplanting them to soil. The brittle "water-formed" roots often break during transplant & those that don't break are very poor at water absorption and often die. The effect is equivalent to beginning the cutting process over again with a cutting in which vitality has likely been reduced. If you do a side by side comparison of cuttings rooted in water & cuttings rooted in soil, the cuttings in soil will always (for an extremely high percentage of plants) have a leg up in development on those moved from water to a soil medium for the reasons outlined above. Al

That is another JOY of wintersowing- I just reuse the dirt. I don't feel the need to sterilize the soil before using it again as damp off and black flies are simply not a problem when wintersowing. I have done this for a few years now- and the only drawback I see to reusing the dirt is sometimes I get something to sprout the second time around that didn't do it the first time and I have to do some research to figure out just what that strange thing is! When I sowed indoors under lights I used to bake my dirt in the oven - to sterilize it- and would stink up the whole house! I have heard of microwaving it- but this is the first time I have heard of double boiling it. I hope you can use one of those out door turkey frying setups so your house doesn't smell of cooked dirt like mine used to! I would attempt to reach a certain sustained temp for a while to sterilize it- I am sorry - I forget now what that temp was- maybe 250 degrees but I tried to maintain it for 30-60 min. I wonder if heating the gel might cause it to change it's chemical make up and release toxins- many plastic and petroleum based products will do that- It might make sense to look into that before attempting to heat it up too much- Hopefully I have offered useful tips- even though I could not offer the answer you asked for- Julie