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

I often wonder if those things are really a good idea. How available is that moisture to the plant? Constantly wet soil isn't good for many plants - the roots will start to rot. I've read where some people have stated that the soil in the pot has stayed moist for weeks with water retentave agents put in. I haven't read anything to establish or refute this concern, so I may be worrying about nothing. I guess it would depend on how often you need to water with these crystals added. There are other concerns though - what are the crystals you're using made of? Starch based ones are safe, and while polyacrylamide hydrogels (PAMs) are safe enough to use, they degrade into acrylamide, which is a neurotoxin and a potent carcinogen. Ultraviolet will cause PAMs to degrade. Acrylamide isn't taken up by the plant roots, and it breaks down itself very quickly, so it's not a long term or serious danger, but it's a good thing to know of any risks associated with any product. The other big concern is that PAM hydrogels have been shown to cause decreased uptake of several nutrients (magnesium, iron, and calcim), so even though you're fertilizing, the plants might not be getting all the minerals it needs. I think if you're going to go the route of using something like this, I'd skip the expensive crystals, and just stick a diaper at the bottom of the container (diapers do contain exactally the same substance - PAM hydrogels). That way the exposure to UV will be almost non-existent, and you can use all the money you saved to buy another plant :-) You also might want to fertilize with a more dilute fertilizer a bit more often. BP

Hi Jayinjay, "Watering from the bottom isn't really an option... I have about 150 plants that just barely fit under the lights. Moving them twice a week to water from the bottom would be too time consuming and I haven't been able to find a plastic bin or tray suitable for holding them, that wouldn't take up too much space where they would still fit under the lights." I think the advantages of watering from the bottom would justify the effort of finding some trays. I have used my PermaNest trays for many years. I have also used some cookie sheets that I got from Walmart as trays. The cookie sheets can act as shallow trays. The cookie sheets add maybe a quarter of an inch of elevation, while the PermaNest trays add maybe a half an inch. It is vastly easier to flood a tray and simultaneously water all the pots in it than to try to water the pots individually. And if your shelf is reasonably level, you can add the water to the tray from the front without moving anything. Good growing mediums will "wick up" the water all the way from the bottom to the top. I use Premier ProMix BX. ZM (not associated with any product or vendor mentioned)

Soil-less mediums work best for containers because they maintain viable structure and porosity. Soils and soil based mediums work in the ground because they become part of a much larger system. Once you take real soil out of that system....it no longer functions. Soil-less mediums (potting soils) provide anchorage, plenty of good air spaces (a requirement for germination, rooting, and normal plant development), and available water. Sand, silt, and clay are all of the soil components that work great FOR us in the garden, but AGAINST us in containers. Poking holes with a solid object compacts the soil around the holes. True aeration would remove columns of soil (like a core aerator for lawns). Best to incorporate something that provides nice pore spaces throughout the entire volume within the container. Seeds, also, need oxygen in order to progress properly, as well as moisture. That's why a soil-less medium IS ideal, if you are germinating seeds in containers. Most (so called) germination mixes are made of very finely milled peat moss, along with vermiculite and perlite. Those ingredients work to provide a steady supply of available moisture and oxygen. When I'm germinating seeds, I fill most of the seed flats with a very coarse textured potting medium, followed by a layer of the germination mix. After sowing the seed, I'll cover the seeds (if required) with more of the germination mix and use my misting nozzle to saturate the entire medium. The germinating mix insures that the seeds will have contact with the moisture providing peat. By the time the seedlings have begin to grow a little, their roots enter the highly porous medium.....then LOOK OUT! ;-) My potting mix is made of composted bark fines, peat moss, perlite, coarse granite grit (like for poultry), and Turface.