Anne you won't find a bigger fan of DE in seed starting than me but it has real drawbacks when it is used when trying to harden off seedlings. I have used it successfully but I have also run into problems with it when it was too hot and it dried out too much. I swear it looks almost like it can actually suck the life out of the plant if it dries out completely where as the plants seem to recover fine when the medium is potting soil. I find using larger containers of DE much more difficult to manage than when I am using it for seed starting because they don't bottom water as well as small containers of DE and it is hard to tell if the DE is too dry once the surface gets a little algae stain on it. I killed a bunch of onion seedlings last year when I let the 8" clay pot they were in dry out too much.
I am potting my grafts up into moist Optisorb as I graft them and then put them in the healing chamber and it has really helped prevent damping off in the healing chamber. When they are ready to go outside to harden off I am re-potting them again into cups with potting soil. I have left a few in the DE but I have to keep a close eye on them as they are tending to dry out far too fast when exposed to the sun and wind. We haven't even had a hot day yet so I may pot the rest up into pots with potting soil because even though it was only in the low 70s today the DE cups were very dry after being well watered just 24 hours earlier. When the plants are that small they don't remove the moisture that fast so it is obviously evaporating much faster out of the cups with Optisorb than the ones with potting soil. I like letting my tomatoes dry out for added root vigor but I don't like some of the effects of letting them dry out when they are in DE. I imagine with your low humidity in California that the problem would be even worse.
My grafted and ungrafted seedlings have been getting a weekly dose of Urban Farms Apples and Oranges which is very similar to the Vegetable fertilizer which I used last year with good results. I give mine about a 1/3 to 1/2 strength feeding about once a week but they get watered 2 or 3 times between feedings and I have had no problems. When they get out in the garden and get to the early bloom stage I will start giving them a weekly dose of TTF. I usually start off around half strength when the plants are small and increase the strength as they get larger and also the overall amount. Whenever they get really dark green I will reduce the dose or just give them plain water until they look like they are ready for more.
Bill
|