Harvest Your Bin
When your bin is full of rich, dark compost, it's time to harvest your worm castings.
Worm castings (vermicompost) are one of the most nutrient-rich fertilizers you can give your plants. Harvesting is simple and takes about 30 minutes. Here's how to do it.
When Is It Ready?
Your bin is ready to harvest when most of the bedding and food scraps have been converted into dark, earthy-smelling compost. This usually takes 3–6 months depending on your worm population and feeding habits. You'll notice the bin looks more uniform and the original bedding is no longer visible.
Two Easy Harvest Methods
The Migration Method (Easiest)
Stop adding food to one side of the bin for 2–3 weeks, then start adding food only to the other side. The worms will migrate toward the fresh food. After a few weeks, scoop out the finished compost from the empty side — most worms will have moved away from it. This is the gentlest method and requires the least sorting.
The Dump and Sort Method
Spread a tarp or plastic sheet in a bright area. Dump the entire bin contents onto it in small cone-shaped piles. Worms hate light and will burrow to the center of each pile. Scrape off the outer layer of finished compost, wait a few minutes, and repeat. After 3–4 rounds, you'll have mostly worms left in the center. Return them to the bin with fresh bedding.
After Harvesting
Refresh the bin
Add fresh moist bedding (shredded newspaper) to the bin before returning your worms. This gives them a clean start.
Return the worms
Place your worms back in the refreshed bin. They'll quickly settle in and get back to work.
Cure the castings (optional)
Let the harvested compost sit in an open container for a week before using. This allows any remaining worm eggs to hatch and any ammonia to off-gas.
Use your compost
Mix worm castings into potting soil, sprinkle around garden plants, or brew into worm tea. A little goes a long way — even a 10–20% mix dramatically improves plant growth.
How to Use Your Castings
- Mix into potting soil at 10–20% by volume
- Top-dress garden beds and work in lightly
- Add to seed-starting mix for stronger seedlings
- Brew into worm tea for a liquid fertilizer
- Use as a lawn top-dressing in spring