I have a large perennial bed that needs to have the soil rejuvenated – it has been several years since the bed was installed. I dread having to dig up all the perennial plants, work the soil and then replant everything. Can I achieve the same benefits by placing a thick, 4 to 6 inch layer of organic matter over the bed this spring? Will that smother and kill the perennials, or will they gradually work their way up through the added layer? Would it be possible or better to do this in the fall after the plants are done blooming?
Adding a large layer of organic matter at one time will cause the crown or base of most of the perennial plants to rot and die. A small layer of organic matter 1 inch thick can be worked into the soil each spring and fall without causing the plants to rot. A commercial fertilizer may also be applied to provide nutrients for the perennials. A fertilizer such as 9-21-14 is recommended.