The problem with this well-intended advice?
- Fall leaves form a thick mat on the soil, which holds water tightly against perennials’ crowns and causes them to rot. If they don’t rot, then they have trouble getting through that mat of leaves in spring and will come up scraggly and thin.
- If you have a pretty layer of wood chip mulch to prevent weeds or if you are using landscape fabric, once the leaves break down and become compost, you will have a layer of really fantastic compost, i.e. Weed Seed Nurturing Soil Mix, sitting on top of the stuff that’s supposed to be keeping weeds from germinating. Whoops!
- And lastly, matted-down leaves on the lawn or on groundcovers can cause dramatic bare spots in a matter of weeks. In one garden I know of where the natural look is preferred, a drift of leaves killed all of the foliage on the Blue Star Creeper groundcover that was acting as a small-space lawn in just a couple of weeks. Then weeds put up a fight to take the space over while we coddled the Blue Star Creeper back to life!