Top dress in spring and fall with approximately 1/4 in of Mushroom Compost. Flower and vegetable gardens, spread mushroom compost two to three inches deep over garden and till to a depth of six inches prior to planting. Shrubs, trees and evergreens, mix one part mushroom compost and one part existing soil. Increase to two parts of mushroom compost to one part all American top soil if existing soil is poor.