After you have fed your worms for three to six months, you’ll see some worm compost in the bottom of your bin. You can harvest what’s there, or wait until your bin is nearly overflowing. No matter which method you use, some worms will remain in the compost. Worms put in the garden with the compost will not live long, but your main goal is to reserve enough worms to re-start your bin. You can’t save every worm! Here are a few methods for harvesting the compost, with Methods #3 and #4 the most effective in separating the worms from the compost you're taking out of the bin.
Method #1:
Most of the uneaten food, bedding and worms will probably be in the top third of your bin. Remove this material, worms and all, and put it aside to start a new bin. Remove the remaining material from the bin for use as worm compost. Put the uneaten food, bedding and worms back in the bin, and resume feeding and maintaining your bin.
Method #2:
This method works only in bins over three feet long. Move the contents of your worm bin to one side, place fresh bedding in the empty space and bury your food wastes there for a few months. Harvest the other side after most of the worms have moved into the new food and bedding.
Method #3:
Spread a sheet of plastic out under a bright light or in the sun. Dump the contents of the worm bin and build a few cone shaped piles on the sheet. Gently remove the top layer of each pile until you see worms. To escape the light, the worms will dive deeper into the piles. After repeating the process every 20 minutes or so for a few hours, you will be left with a wiggling pile of worms. Save your compost and return the worms to their bin and fresh bedding immediately. Here's a drawing of this method of Worm Separation.
Method #4:
If you are using a manufactured worm bin with stacking trays, try this easy way to Harvest Tray Castings.
Using Your Worm Compost
Using your finished product will help your plants thrive by adding plant growth hormones, beneficial microorganisms, humus and nutrients to the soil. Pure worm castings - black with a smooth pudding-like consistency - are the "black gold" vermicomposters strive for. Mix a handful in a 5-gallon bucket of waters and stir vigorously to make wom tea, which can be used to water all your garden and house plants. Castings will maintain their nutritive qualities for several months stored in the dark with access to air but kept moist. If they dry out, castings will become hard nuggets that are no longer useful. Due to effect of drying, it is not advised to apply worm compost on the durface of the soil, but you can blend worm compost up to 20% into potting mix or garden soil.