Drive down an urban or suburban road. Notice that most towns and cities will have street trees. A rich variety of maples, oaks, sweet gum, magnolias, sycamore offer us shade and beauty on our streets. Some of these trees are native to Michigan and others are not. Some may have been grown to withstand the harsher conditions of living roadside. Down the road from me, some oak trees have recently been planted. They are small now but could grow over time to 40 feet tall or higher.
Is this tree in the mow strip by the road an ecologically sound habitat? Probably not. There is grass that is constantly mowed in the summer months. Typical lawn grass only has roots that extend 3-6 inches into the soil, so insects have less access to soil they burrow into since the mowing compacts the ground. Additionally, many yards have the little warning signs that they have been sprayed with herbicides or insecticides. If an oak gall wasp larva or cicada larva is under the ground during the time this spraying happens, they will never emerge to lay their eggs. There is no leaf litter where organisms like fireflies and moths may have overwintered. Certainly, moths and butterflies can lay their eggs on the leaves, caterpillars can munch and birds can take their fill of this food for themselves and their hatchlings. But, there is a limit to the life cycles of a lot of the insects that benefit from these particular city oaks.
What can we do to create a more habitable place for a wider range of life to occupy these spaces? It can be a challenge in a city with ordinances limiting what can be done in the street tree space, so let’s instead imagine an oak or wild cherry tree in a backyard. Maybe this is a tree that has a child’s swing hanging down, or where a tree house has been built. The lower branches are high enough that the lawn can still be mowed, and so it has been, for years. But you now understand that there are a lot of living beings that rely on a tree and its surroundings to survive. What can you do?
The first thing is to ditch the lawn. Let the leaves fall in the autumn and just let them sit on the ground. You may want to take a more active approach that involves layering cardboard and mulch or cardboard and leaves to smother that lawn, but even just letting those fall leaves stay on the ground is a vast improvement over raking them so the lawn can be mowed the next spring. If you are ready to take another step, let’s go back to the concept of soft landings.
Leaves that are consistently left on the ground and allowed to decay year after year begin to prepare the soil underneath for another kind of existence. One more like you might see and experience on a nature walk or hike. What is going on under native trees in a natural setting? You will likely see some leaves, maybe some bare soil, sedges or grasses, herbaceous plants, and a shrub or two. With these additional amenities, it is easy to see that more organisms will benefit. Now instead of only tree-nesting birds, there may be some ground-nesting birds that will benefit. If there is a vernal pool nearby, salamanders may live under rotting leaves and logs. Several more moth and butterfly species may be seen around since there are different kinds of vegetation to support larval stages as well as nectar requirements. Fall birds may stop by the berries on a shrub under the tree. A box turtle may meander through the plants. Snakes may slither eating rodents and insects on the ground or up in the tree.
You can take this same idea to your own yard. The plants and decaying leaves under trees, out to the drip line, are the soft landings that I referred to above. It’s what enables larva to fall out of a tree, safely land, and have the needed soft soil and organic material to move to the next phase of its life. It’s some open soil where a mining bee may dig a nest to raise her brood. It’s the plant stems left from year to year to provide nesting spots for other native bees. It is leaf litter for firefly larvae to overwinter. Beetle grubs can grow and pupate to emerge without the threat of pesticides that will kill them. Parasitoids will be able to find their specific host insects so they can reproduce as well. Plants growing under the native trees provide shelter and food for other wildlife.
Wild Ginger Woodlands and other Michigan native nurseries offer plants that can be grown under trees to provide these soft landings. Most people will want some wildflowers, however please also consider grasses, sedges, and ferns. While people may enjoy a tidy looking garden, birds and other wildlife tend to enjoy a “wilder” look with plants of varying heights and widths and structure.
In the future, Wild Ginger Woodlands will be offering a few small garden designs and ideas that you can use to create your own soft landings! Stay tuned.