The worm tower at my Varsity Community Garden plot is made from a lightweight but very durable 10”-diameter cylindrical cardboard tube used by builders for concrete post footers. I bought the cardboard tube from a home improvement store rather than a 4” diameter PVC pipe that may be toxic to worms and plants.
The tube is made of water-resistant high-strength fiber that is easier to cut and drill than PVC pipes. Some tubes come in 12” diameter but the 10” is the perfect size for my small raised bed. I have to do more research on this product in case the glue and other materials used to manufacture it may also the put the worms and the plants at risk.
I cut the tube to the 3-foot length for my worm tower, drilled a dozen or more 1-inch holes all around the bottom half or below-ground portion of the tube, and set it halfway into my raised bed. The holes allow the compost tea to be released into the soil and nourish the roots of the nearby plants. Moisture is assured because my garden plot is a raised wicking bed in which the soil above the water reservoir is the plants’ primary source of water.
A handful of red wigglers were added to the moist shredded newspaper and food waste inside the tube. I don’t expect these worms to use the holes to exit the tube to deposit their poop in the soil then return to eat the rotting food waste. Unlike the Canadian and African night crawlers that live in soil, red wigglers prefer the surface where they live beneath the organic debris on the forest floor or the farmer’s field. They are excellent for turning food waste into compost. The worms are from my home vermicompost bins.
In order to prevent sunlight and predators from entering the tube, I used a pot that fits snugly on the top opening. The drain hole allows rainwater to drip into the composting waste in small amounts, just enough to moisten the worm compost and facilitate compost tea movement to the surrounding soil at the plants’ root zone. Three cherry tomato seedlings were planted inside tomato cages around and 10” away from the worm tube to allow the plants enough room to grow.