ROARK: Roadside forests

By Steve Roark

It’s a given that in our mountainous terrain you’re going to see trees while driving down the road. Most of them are growing in natural forests with good soil that supports a wide variety of species.  But some trees you see especially close to the roadside are not growing in natural conditions, but on road cuts. These are places where soil and rock were removed to make way for the highway and are plentiful in hilly terrain. Conditions at these sites are harsh for growing things, and yet certain tree species and plants are able to make a go of it.

Around 50 years ago road cuts were made vertically, creating highwalls of solid rock. These were simple to construct and took up a minimal amount of land but created a problem of rocks breaking off from weathering and becoming a hazard to vehicles and over time filling up ditches with debris.  On more recent road construction projects, the cuts were made further into the hillside and angled to create a slope rather than a vertical wall, often with flat benches cut out to catch any rolling rock. These slopes require a lot more land disturbance and have a surface of highly compacted rock and soil, lousy places to grow a tree.  And yet nature finds a way by providing some species with root systems that can eke out enough water and nutrients to survive in really bad conditions, and these are the ones you will observe. The trees got there in the usual way, seeds brought in by birds pooping seed or carried on the wind. Some of these trees are showy and catch your attention, and here is a sampling of trees you will most likely see on roadcuts.

The evergreen ones:  Red-cedar and Virginia pine are some of our toughest trees and are very common on roadcuts. They can literally grow out of cracks in solid rock. From a distance cedar have rounded, dense canopies, while the pines are lacy with spaces between the limbs.

The showy ones: Some roadcut trees put on quite a show of flowers during the spring and this is when they’ll get your attention. Purple flowering Redbud is a native tree that everyone is familiar with and bloom heavily in April.  Paulownia is a non-native tree that has large purple flowers that bloom in May. In fall and winter, it can be identified by seedpods that look like clusters of large grapes. Bradford Pear has escaped into the wild from the thousands that are planted in home landscapes and have showy white flowers that bloom in late March-early April. Paulownia and Bradford Pear are classified as invasive and despite their pleasing look are not welcome in the wild. Autumn Olive is a shrub with olive colored foliage during the summer and showy red berries in October.  This is another invasive that is rapidly spreading by birds dropping seeds.

The Other Ones:  There are several trees growing on roadcuts that are not aesthetic standouts, but common at these sites, including sycamore, boxelder, black locust, and sweetgum. Non-tree plants often seen on roadcuts include fescue grass, broom-sedge grass, and some clovers.  Mullein is a herbaceous plant with a tall stalk of yellow flowers that bloom during the summer.

A benefit of trees growing on the roadcuts is that their roots provide additional soil stabilization, and like their natural counterparts growing in mountain forests, help hold the world together. My thanks to Luke Boyd for road engineering insights.

Steve Roark is a volunteer interpreter for the Cumberland Gap National Historical Park.