Create stronger canopy with urban forest diversity with native trees | Jody Walthall

Tallahassee is fortunate to currently have a considerable urban forest, though it is constantly being whittled away through development, storms, and fear of storm-related damage to homes. The average tree canopy is rated at 55% of land.

This average puts Tallahassee close to number one in the nation for urban forest coverage. One problem with our forest is the lack of diversity in the species make-up.

According to the City’s Urban Forest Master Plan three native trees (Carolina laurel cherry, water oak, and laurel oak) and one highly invasive non-native tree (Chinese camphor) are short lived, weak wood species that make up a full 38% of the forest. The long-lived sturdy live oak makes up 7% of the forest.

The diversity of tree species has an impact on the overall health of the forest, its wind resistance, and the food value for wildlife, from invertebrates to mammals. In terms of wind resistance, the four species making up this 38% are all considered to have very low wind resistance.

If you are concerned about tree damage during a storm, choose smaller trees such as holly, greybeard, flatwoods plum, redbud, and red buckeye. The most wind resistant large trees are Southern magnolia, live oak, sweetgum, cabbage palm, pecan, and red maple.

For wildlife food, always turn first to American native species. Don’t put your entire focus on berries for birds. Berries are important seasonal sustenance for birds, especially during migration, but insects are the key to healthier food chains.

As an example, birds will eat the berries of Chinese camphor and spread seeds all around town, growing the percentage of Chinese camphor in our urban forest.

Meanwhile, there are few insects that can find sustenance on this foreign tree. In contrast, native oak trees in our area can host 395 species of butterflies and moths in their larval form as caterpillars.

A native red maple may host 171 species. These caterpillars are functionally soft bags of proteins for birds, lizards, frogs, and other wildlife.

Caterpillars are not the only insects in our native tree canopy. Thousands of species are on the leaves and branches, though we seldom see them. Many insects try to hide or use deception and stillness to survive the winter.

Our resident and migrating birds search the treetops like a fine-tooth comb looking for this source of food, yet the insects are usually no threat to the tree or humans. Don’t fear the bugs!

Search the National Wildlife Federation’s Native Plant Finder and enter your zip code; the site will show how many species of caterpillars use particular native plants in your area. This tool can help you select a tree for your yard.

A diverse native tree canopy is a major component of a healthy ecosystem that we need for human survival. What happens to us if we do not have trees supplying nectar, pollen, and leaf food to native pollinators?

The flowers of trees such as red maple, black gum, black cherry, magnolia, tulip poplar, dogwood, redbud, Chickasaw plum, Southern crabapple, native hawthorns, and sassafras all supply nectar and pollen for bees along with hosting insects for many types of wildlife to eat.

If you have native trees in your yard, be sure to leave the leaves on the ground where they fall. Experts suggest leaving the leaves out to the dripline of the tree’s branches. Hundreds of species of insects live in the leaf litter. Some moth caterpillars eat no green leaves, consuming dead leaves on the ground exclusively.

Many moths or butterfly caterpillars drop to the ground and hide in leaf litter to spend the winter in a cocoon or chrysalis. If lawn grass is beneath the tree, they usually die. Other insects merely hide through the winter, often becoming food for birds and other wildlife.

Dead leaves are a critical part of a healthy ecosystem. I give you permission to be lazy – leave the leaves! If you prefer to have some open lawn in your yard, as I do, just rake the leaves into existing beds.

As our city population grows, we clear cut and bulldoze hundreds of acres of stately trees for apartments, houses, parking lots, and roads. If you have open space for trees in your yard, you can help make up for this loss. There are too many beautiful and useful species of trees to mention.

Some large trees to consider are winged elm, Southern red oak, white oak, Shumard oak, swamp chestnut oak, basswood, mockernut hickory, and bald cypress. Rather than the smaller non-native Drake elm or crape myrtle, choose blue beech, hophornbeam, silverbell, hoptree, Hercules club, American olive, or redbud. Choose a tree based on your soil and sunlight conditions.

Trees, especially live oak and pine, give Tallahassee a sense of place. They are so valuable for multiple reasons: preserving our mental health; cooling our streets, parking lots and homes; creating beauty; sequestering carbon; controlling erosion; naturally feeding wildlife.

Every yard matters and every tree counts. What you plant in your own yard makes a difference to the local food web. If you have room for more trees in your yard, winter is the best time to plant.

Jody Walthall is retired co-founder of Native Nurseries and a volunteer writer for UF/IFAS Extension Leon County, an Equal Opportunity Institution. For gardening questions, email the extension office at AskAMasterGardener@ifas.ufl.edu.

This article originally appeared on Tallahassee Democrat: Create urban forest diversity with variety of native trees