tea leaves are excellent for plants. Simply empty the contents into your garden for use as compost. Rather than rushing out into the garden with every used bag, it’s a good idea to empty the tea bags as you use them into a container so you can build up a batch of tea leaves. But don’t leave it too long before emptying.Fertilize roses: Spread used tea leaves around rosebushes, then add mulch and water. The tannic acid and other nutrients will benefit the plants.