Soft Landings Benefits Insects and Gardeners

New housing and shopping areas are often desirable improvements to any human community. However, what benefits one species can be detrimental or devastating to others.

Displaced wildlife populations, including insects and pollinators, need new homes. As they flee from developed woods and fields, these tiny citizens retreat to our manicured lawns to raise young in trees that usually have clipped grass or mulched beds at their bases. These landscaping methods, unfortunately, result in an inhospitable wasteland for many forms of life.

One way to help wildlife is to share a small portion of our yards using a method called "soft landings." Conceived by Leslie Pilgrim, a conservation gardener and executive director of Neighborhood Greening, a nonprofit in Minneapolis, and biologist, pollinator conservationist, and award-winning author Heather Holm, a soft landing is a gentle gardening technique that replaces the traditional lawn under a tree with native shade-loving plants, leaf litter, and tree branches. Many species of moths and caterpillars need to complete their life cycles hidden under duff, a protective layer of leaf litter and decaying plant material. Sheltered from the blades of the mower and weed trimmer and hidden from the eyes of predators, insects that the tree once hosted in its canopy easily find shelter under the tree to develop into adults. Beneficial insects such as beetles, lacewings, bumble bees, and fireflies also enjoy this homegrown nursery. Some surviving larvae and adults become food for other species, such as birds. Adult birds can survive on seeds, nuts, pollen, or nectar, but hatchlings require a nearby supply of caterpillars and moths.

The perimeter of this safe zone is easy to trim around. It reduces harmful soil compaction from mowers and accidental trunk damage by a weed trimmer. Birders often make exciting discoveries, as the growing soft landings habitat attracts birds and wildlife.

While deciduous trees and conifers benefit from a soft landings approach, keystone trees such as oaks (Quercus spp.), willows (Salix spp.), cherry (Prunus spp.), pines (Pinus spp.), or poplar (Populus spp.) are a strategic, preferred choice. Keystone trees host a larger variety of insect species compared with non-keystone trees. As such, keystone trees offer superb ecological value when planting space is limited. For instance, according to the National Wildlife Federation, oak trees can host over 952 caterpillar species.

Under a shingle oak (Quercus imbricaria), Penn State Master Gardeners of Butler County established a soft landings demonstration garden on the Native Plant Butterfly Trail, which is located just off the North Country Trail at Moraine State Park near McDanels Boat Launch.

To create your own soft landings, select an existing healthy native tree or consider planting a new keystone tree. Identify and save any existing native plants beneath the tree while gently removing invasive plants. If turfgrass is present, cover it with a layer of cardboard, leaf debris, and branches. Using a small hand spade, install plugs or cell packs of low-growing, partial-shade, or shade-tolerant native perennials. Add plants up to the edge of the overhanging tree branches (dripline). Avoid digging within three feet of the tree trunk, where sensitive roots and root flares are located. Adding extra soil or compost is not recommended, as this can suffocate the root system of the tree, which needs to breathe. In the fall, rake in leaves and twigs to build up the duff layer.

Install native plants that make soft landings attractive to pollinators in spring through fall. Red columbine (Aquilegia canadensis), a woodland beauty with drooping bell-like red, pink, or yellow flowers, blooms from February through August, peaking in May. Columbine is a host plant for the columbine duskywing butterfly (Erynnis lucillus). It is also a popular nectar source for butterflies, hummingbirds, and long-tongued bees, including leaf-cutting bees (Megachilidae), miner bees (Anthophoridae), and bumble bees (Bombus spp.). The showy pink, purple, or white flowers of spotted geranium (Geranium maculatum) appear from March through June. This plant spreads by rhizomes but is not aggressive and attracts many pollinators with pollen and nectar; its seeds are valuable to wildlife. Common blue wood aster (Symphyotrichum cordifolium) has pale blue to violet flowers, which bloom from August through October in part shade to full sun. Attractive to bees and butterflies, the common blue wood aster is the host plant for the pearl crescent butterfly (Phyciodes tharos).

Penn State Extension offers additional information about keystone plants and soft landings. In addition, Penn State Extension Master Gardener Lisa Schneider hosts two informative videos featuring soft landings in the "Year-Round Gardening" series produced by WPSU. Biologist and author Heather Holm's website provides a list of flowers, grasses, sedges, and ferns for soft landings that are regionally appropriate and thrive in partial shade.