I tried this last year with a folded bottom sort of method and it was only somewhat successful, but then I came across this lovely blog, Chicken in the Road, and wow!  This is sooooo easy.  I'm hoping these pots are more stable than my folded ones.

Here are samples of my own handiwork:

As you can see, they fit nicely into the "greenhouse" made from repurposed salad green containers!  I figure 18 will fit nicely.

Now I have a reason to look forward to replacing rolls of paper towels and toilet paper!

For more Tightwad Tuesday, see Mary's blog!