As a side note: if you have kids, this is a good project that they will enjoy helping with.
I don't know about you, but every year I start quite a few seeds inside to get a jump on the season. I'm in Zone 5A so my plants need a little head start! I don't have a greenhouse (not yet!!). Instead of purchasing dozens of those little peat pots, why not use empty toilet paper tubes instead? They biodegrade, and will enhance your soil. Another bonus: you've already got them in your house, so no purchases need to be made. Free stuff is good!!!
Paper towel tubes are also excellent, as they are almost exactly the same diameter. Each paper towel tube will yield 3 pots. You can also be creative and use empty cardboard tubes from gift wrap. Some of the gift wrap tubes (especially from Christmas paper) can be quite wide and are helpful for planting more than one seed, such as squash, pumpkins, melons, etc.
Why am I talking about this now? It's November, and many of the people in this country aren't even planting any gardens now! What am I thinking?!? Well, if you start saving your empty paper tubes now, you'll have plenty saved up by spring to get your garden off to a great start! So start saving!
Here's how I make my little homemade paper pots:
For toilet paper and paper towel tubes: Make cuts (one inch long) into one end of the tube. Space these cuts about a half inch apart. Continue doing this until you've gone all the way around one end of the tube.
Next, simply fold these "tabs" inward to form the bottom for your paper pot.
For wider tubes: Make the cuts long enough so the tabs will span two thirds of the way across the open end of the tube when you fold them over. You should space your cuts a bit farther apart for these bigger tubes, too. Then fold the "tabs" in the same manner as for the smaller tubes.
Next, fill your new paper pots approximately 80 - 90% full with your favorite potting soil, and pack it slightly to eliminate any air pockets. Then plant your seeds. Oh, I should mention that if you live in a cold climate, and your potting soil is kept in the garage or outside, you will need to make sure your potting soil is at room temperature before planting to allow for good seed germination. Overnight usually allows enough time for the soil to warm up. Once your soil is in, and your seeds have been planted and watered, the pots tend to hold their shape well. You can write the plant ID right on the paper pots so you can keep track of what's what until planting time.
To keep it all together and waterproof, I use plastic seed starter trays (that I've had for years). The variety I use have black bases and clear plastic lids. I've seen many of the big box home centers carry these. The brand I use comes in 2 different sizes (1 1/4" and 1 3/4" peat pots). I use the larger one. Minus the peat pots of course.
The real beauty is that toilet paper and paper towel tubes are perfectly sized to fit into the little indentations in bottom of the 1 3/4" trays. I just love it when things work out this nicely! The jumbo-sized paper pots (e.g. Christmas wrapping paper type I mentioned) work better in the lid, but you'll need to take measures so they don't tip over because the lid doesn't have any perfect-sized indentations like the base has.
When removing your paper pots from the tray, you'll probably need to slightly twist them to safely lift from the tray. Sometimes little roots will grow out of the opening at the bottom and they may intertwine. There are no special steps are needed when transferring your plants to your garden.
PS. This idea works very nicely even if you do have a greenhouse.