Jane Tunks, a novice gardener, is using The Chronicle's rooftop garden as her classroom, with Fred Bové and Kevin Bayuk from the San Francisco Permaculture Guild as her teachers. Here is another of her lessons. Read other stories in the series at sfgate.com/columns/chroniclegarden/archive
Make your own worm bin
You can build a worm bin in less than an hour by following these steps. You'll need two 20-gallon plastic storage bins with lids, a permanent marker, a Sunday edition of The Chronicle, a drill with 1/4-inch and 1/8-inch bits, red wiggler worms (Eisenia fetida), kitchen scraps and two 1-gallon plastic pots. When your worm bin is complete, store it in a cool, shaded spot either indoors or outdoors.
1. With a permanent marker, draw 10-15 evenly spaced dots on the lid of one storage bin.
2. Drill through the dots using the 1/4-inch drill bit.
3. On the sides of the same bin, about 1 inch from the top, draw one row of dots 2 inches apart.
4. Drill through the dots using the 1/8-inch drill bit.
5. On the bottom of the same storage bin, draw 10-15 evenly spaced dots.
6. Drill through the dots using the 1/4-inch drill bit.
7. Tear newspaper lengthwise in 2-inch-wide strips and put in the storage bin until it's about two-thirds full.
8. With a garden hose, spray water on the shredded newspaper until it's just wet and turn until it's evenly coated with water. Once wet, the newspaper should fill the bin about halfway. Add more wet newspaper as needed.
9. Place red wigglers on top of the wet newspaper, along with kitchen scraps - we gave them overly ripe heirloom tomatoes from The Chronicle's test kitchen. (Do not give the worms any citrus, spicy food, or dairy or animal products.)
10. Tuck the worms into their new home by placing more wet newspaper on top of them and their food.
11. Place two empty 1-gallon plastic pots at the bottom of the second storage bin (they will act as risers), and put the bin with the worms and the airholes on top of it.
12. Put the lid of the second storage bin underneath both bins; it will act as a sort of coaster, to catch any excess moisture from the bin.
13. To feed worms, lift up top layer of newspaper and add more food, then nestle newspaper back in its place. Put food on one side of the bin at a time.
14. To harvest vermicompost, put new food on the other side of the bin. The worms will move toward the new food, leaving their castings behind. Pull up the top layer of the newspaper, remove the castings. Replace the top layer of the newspaper and use the castings in your garden as needed.