For seed starting, I like to use 1/2 gallon orange juice paper cartons. The nice ladies at church save them for me. They like to help and recycle with things they usually throw away. (they also save shopping bags for me to bag my sales at the farmers market and greenhouse in!) Throw away the plastic lid, cut them in half lengthwise to make two long trays from each carton.
5 halved cartons will fit in a no holes flat, covered with a clear germination dome. So you can do 5 different kinds of seeds in there, and take them out as each one germinates.
I dip all the cartons and flats and domes in 1 T Physan 20 to one gallon of water. Then fill with a good seedstarter mix that's sterile-like my favorite- Promix PGX with biofungicide. If using promix with biofungicide, fill containers with soil and water in the kitchen sink with warm water until moist. Don't use Physan or it'll also kill the biofungicide built in.
If using other mix, fill with soil and water in using 1t Physan 20 to 1 gallon warm water. Then plant seeds. As a tip, don't put seeds in there too thickly or no matter how much light you put them in,they will be spindly when they are overcrowded. 50-75 tomato seeds, banana seeds, or other large plants is max. You can sometimes put up to a seed packet of small seeds like snapdragons that grow slowly as seedlings.
If you're doing tropicals that take a long time to germinate, presoak them for 15-20 minutes in 1 t Physan to 1 gal water to sterilize the outside of the seeds to give them a better chance not to mold before they come up.
Then cover with the sterilized cover and here's the cool part, if you have the right kind of furnace, a gas forced air one with heat vents in the floor, then you can put them on your FREE heat mat!
My FREE heat mat is my forced air central furnace with floor ducts. You take a empty web flat, the ones that look like mesh on the bottom, and have openings on the sides, turn it over and sit it on top of the heat vent. Then you sit your germination dome covered flat on top of it. The heat will heat your flat and also your room because it can go through the mesh flat. If you don't have one of those mesh flats, a cookie cooling rack will work, even a cookie sheet elevated on a couple of bricks will work. Just so that the heat can still get out into the room and also will heat up your container of seeds at the same time.
Check your seeds every day, and get them in bright light asap and uncovered asap if they are sprouting. I put them out into my greenhouse.
You can use bright fluorscent lights etc as an alternative.
When you're growing on your plants, you can carefully take a sharp knife and cut slits in the bottom of the cartons for drainage if you want to, or just water carefully.When your plants grow big enough, cut the side of the carton and carefully remove your plants, using the leaves to pick them up with, not the stems. A plant can grow another leaf that might get ripped off or crushed, but it's not going to grow another stem at this point! Pot them into a good potting mix like Promix to grow on until planting time.
Then when you're done, throw the cartons away. Save the flats and domes for next year after cleaning them up.

Please take a minute and leave feedback for this guide--whether it was helpful to you. Feel free to copy it or use it for your personal use, too.

Sandy Burrell, Northern Tropics Greenhouse, Muncie, IN northerntropics.com