I did a little research on the best way to plant and grow seedlings and plants (starting with tomatoes and peppers) in my home state (Alaska). I started my seeds in doors in one of those plastic green house things. The problem with these things is that the little bit of dirt dries out fast. If a seedling dries out during germination, it is dead. I was thinking of a way to keep the dirt moist to reduce the chances of me forgetting to water them. We use the type of kitty litter that is made from old news paper and made into little pellets. I soaked a few cups in a pan of water for about 1/2 hour until it turned to mush. I mixed that in another bucket with my potting soil. This is what I used to start my seedlings in.
Offered by Clipper.
For hydroponic and indoor gardening they suggest vermiculite and perlite (available at most garden centers). They both suck up and save moisture. I have a big rubbermaid tub for potatoes right now, and a drain near the bottom. If I water more than once a week, the water just drains right out the bottom, because the vermiculite and perlite really hold the water in. I'm sure kitty litter does the same.
Offered by John.
A better substitute for kitty liter is a product that absorbs a 100 times its weight in water called soil moist (it is like silica jell) a dehydrator but better. Reusable thousands of times It is also found in Depends and other diapers as a dry crystalline jell. I am growing radishes in it and potting soil. It only takes a couple of table spoons for a 3 gallon pot.
Offered by Robert.