When it is time to harvest worm castings, which you can use in the garden, below are some of the most popular methods. Top Harvesting: The easiest method, requires waiting for a thick layer of vermicast to form at the top of the soil. Sweep the casting and use your hand to scoop them out of the bin. Be gentle to avoid accidentally crushing the worms. Dry and Sift: This method requires drying the bin by as much as 40%. When moisture is at a minimum, sift to harvest. Migration: This method of harvesting relies on the ability of African nightcrawlers to follow food. You can add food to where you want the worms to go, add a screen or any platform where worms crawl, and wait for them to move out of the bin. Once they are out, all that will be left in the bin would be the worm castings that you need.