Worm castings will help your plants grow. They are the richest natural fertilizer. They are rich in water-soluble plant nutrients and will help the soil retain moisture better. Packed with minerals that will encourage plant growth, they provide those minerals immediately to the plants. Unlike manure that has to be aged, worm castings will not burn the plants. Because of this, you can’t overuse them. No matter how much you use, there will be no harm to the plants. If you plant in containers, work in a layer approximately 1 or 2 inches into the soil. Mix into the first few inches of the soil, then plant as you normally would. They are great as a mulch around trees and shrubs as well.