Early March is time to start planning for the spring planting season, the perfect time to rethink your landscape. I recently read a blog about a great concept. The blog author, Jim Anderson, credits native plant speaker, Gerould Wilhelm, with a simple synopsis—plants live in communities in the wild and should also in urban and suburban plantings. This is not the first time I’ve heard this recommendation. Years ago, Paula Shrewsbury from the University of Maryland did some research on why azaleas get bad lacebug infestations if they are in sunny locations. Since azaleas prefer a partially shaded site, she supposed azaleas in a sunny location might be stressed and send out an attraction signal to lacebugs making the azaleas more susceptible to attack. Her research did not support that hypothesis, but it showed something else. Azaleas growing in the shade are part of a complex community that supports more insects, some of which are lacebug predators. So, it is the complexity of the landscape in the shade that provides biological control of lacebugs resulting in less damage to the azaleas.
In a complex community, like a forest or a multi-level landscape bed (ground layer, shrub layer, understory tree and canopy tree layers), some roots die every year. Those dead roots provide organic matter to improve soil structure and provide channels in the soil for needed air and water to flow to plant roots. If you were a tree, would you rather live as a part of a community with other plants where you get watered and feed by the plants around you or would you rather live in a ring of wood mulch and a shallow-rooted lawn that often forms a barrier to rain and air exchange. Easy choice, right?
In Gerould’s talk he goes on to describe a project at a school in which a first-grade class plants a native tree in a large circle (3-4-foot diameter). The grass is removed, and native plants associated with that tree are planted. If the kids planted a bur oak (Quercus macrocarpa) they could surround it with associated native plants like wild geranium (Geranium maculatum), Jacob’s ladder (Polemonium reptans) and Pennsylvania sedge (Carex pensylvanica). Each year, the class (now second graders) can expand the circle and plant more native plants. Eventually, by about fourth grade, the circle would be big enough to accommodate shrubs or small trees. Imagine a school yard in which each class of first graders progressing through the school was working on its own “tree circle.” By eighth grade, the students would understand the concept of community.
I saw the concept of community in a vivid example last summer when I was biking with a friend in Newark. There is a street where narrow backyards back up to the road. Each homeowner treats their backyard differently, but because they are all lined up, they are easy to compare. To some people, the perfect aesthetic is a clean, neat mowed lawn from the back of their house to the street. Others though, opt for a complex community growing in their backyard. Everyone has the right to their preference and to treat their backyard as they wish. But, when more people chose the community concept, our suburban landscape does a better job of providing the ecosystem services we need to survive. It also results in “happier”, healthier plants.