Controlling Invasive Trees on Roadsides
Thorough guidelines for controlling each of the following species can be found in Cherri Smith's manual distributed by N.C. Department of Transportation.
Please follow this link to get this FREE manual:
http://www.ncdot.org/doh/preconstruct/pe/neu/NEUProcedures/NCDOT_Invasive_Exotic_Plants.pdf
Ailanthus altissima (Tree of Heaven)
Photo credit: Jan Samanek, State Phytosanitary Administration, Bugwood.org
The ability of the tree of heaven to tolerate poor soils makes it a common invasive along roadsides in North Carolina (and all over the country). It is common in urban areas, the mountains, and in the coastal plain.
The tree is small to medium sized with smooth gray bark. It has alternate compound leaves, with 10-40 leaflets along the leaf stem. Each leaflet is lance-shaped.
It flowers in mid to late summer. Flowers are greenish-yellow and grow in clusters. The seeds are light and spread easily through the wind; they are enclosed in a twisted papery pod.
The tree is small to medium sized with smooth gray bark. It has alternate compound leaves, with 10-40 leaflets along the leaf stem. Each leaflet is lance-shaped.
It flowers in mid to late summer. Flowers are greenish-yellow and grow in clusters. The seeds are light and spread easily through the wind; they are enclosed in a twisted papery pod.
Albizia julibrissin (Mimosa)
Photo credits (left to right): USDA Forest Service - Region 8 - Southern Archive, USDA Forest Service, Bugwood.org; James R. Allison, Georgia Department of Natural Resources, Bugwood.org
Mimosa was introduced in the 1700s and is still a popular ornamental tree but it has jumped out of the garden and moved into natural habitats throughout the United States. The tree produces shoots from root sprouts allowing it to form dense thickets which prevents native plants from growing. Seeds are dispersed by animals and through water. It grows best under full sun - so areas along roads and streams are common places for them to grow. The also grow in suburban and urban areas.
The tree (up to 50' tall) is easy to identify in the spring and summer because it produces fragrant, feathery, pink flowers, which resemble pom-poms. In later summer/early fall, it produces oblong, hanging seed pods (6" long).
The fern-like bi-pinnately compound leaves (5 - 8" long) are also distinguishing.
The tree (up to 50' tall) is easy to identify in the spring and summer because it produces fragrant, feathery, pink flowers, which resemble pom-poms. In later summer/early fall, it produces oblong, hanging seed pods (6" long).
The fern-like bi-pinnately compound leaves (5 - 8" long) are also distinguishing.
Elaeagnus pungens (Thorny Olive)
Photo credits (left to right): (olive photo) Ted Bodner, Southern Weed Science Society, Bugwood.org; (leaves and shrub photos) James H. Miller, USDA Forest Service, Bugwood.org
Thorny olive trees were introduced an an ornamental in the 1830s and now they have spread all over the southeast. The seeds are dispersed by animals. It can grow under shade and in sun.
The tree grows densely with many short stems (almost like thorns). it can reach heights of 26' but usually grows much shorter - looking like a shrub. The foliage (2 - 4" long) is evergreen, dark green, oval-shaped, thick, wavy, and silvery-colored on the underside. The leaves grow alternately on the stem. Small white bell-shaped flowers grow in the fall. Fruits sometimes appear; if they do it will happen in the spring. They are red with brown scales and have a silvery appearance.
The tree grows densely with many short stems (almost like thorns). it can reach heights of 26' but usually grows much shorter - looking like a shrub. The foliage (2 - 4" long) is evergreen, dark green, oval-shaped, thick, wavy, and silvery-colored on the underside. The leaves grow alternately on the stem. Small white bell-shaped flowers grow in the fall. Fruits sometimes appear; if they do it will happen in the spring. They are red with brown scales and have a silvery appearance.
Melia azedarach (Chinaberry)
Photo credit: flowers: Chuck Bargeron, University of Georgia, Bugwood.org, leaf: John M. Randall, The Nature Conservancy, Bugwood.org, berries: Cheryl McCormick, University of Florida, Bugwood.org
Chinaberry was introduced in the 1800s and is still a popular hedgerow tree but it has jumped out of the garden and moved into natural habitats throughout North Carolina. It is not as common in North Carolina as it is in other southern states but it is a species to keep an eye on. It is usually seen in roadside ditches and along woodland edges. It can tolerate wet soil and has been seen in marshes. The seeds disperse through birds and it reproduces from shoots and forms dense thickets.
This deciduous tree grows up to 50' tall. Its leaves are large compound leaves (1 - 2' long), meaning they are made up of leaflets which are attached to a central stem. The leaflets themselves are also compound. So, the leaves are described as 'double-compound' leaves; sometimes they are even triple compound. Leaflets are lance-shaped and have toothed margins. They turn golden-yellow in fall. The spring blossoms are clusters of fragrant lavender, 5-petaled flowers. The berries are hard, yellow, marble-sized, and poisonous.
This deciduous tree grows up to 50' tall. Its leaves are large compound leaves (1 - 2' long), meaning they are made up of leaflets which are attached to a central stem. The leaflets themselves are also compound. So, the leaves are described as 'double-compound' leaves; sometimes they are even triple compound. Leaflets are lance-shaped and have toothed margins. They turn golden-yellow in fall. The spring blossoms are clusters of fragrant lavender, 5-petaled flowers. The berries are hard, yellow, marble-sized, and poisonous.
Paulownia tomentosa (Princess Tree)
Photo credits (left to right): Leslie J. Mehrhoff, University of Connecticut, Bugwood.org;Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org
This fast-growing tree (it can grow 15' a year) competes aggressively with native species in disturbed areas in the mountains and foothills of North Carolina and other southeastern states.
It can be identified by its large heart-shaped leaves (arranged oppositely along the branches) and its pretty lavender flowers (on mature trees). The flowers grow in upright clusters during the spring. It produces sticky, green oval-shaped fruits and small, winged seeds. The tree can grow up to 50' and has smooth gray bark (with slight cracks).
Triadica sebifera (Chinese Tallow Tree)
Photo credit: James H. Miller, USDA Forest Service, Bugwood.org
This tree has invaded natural areas in other southern states but so far has remained pretty controllable in North Carolina. However, it can invade undisturbed forests so if it does get out of control it may be a serious threat to native plant communities in forests. So, please keep your eye out for the Chinese tallow tree. It grows usually to a height of 30’ but can be as tall as 60’. The leaves (2 – 3” long) are heart-shaped. Twigs are green to light brown and have small brown dots on them (lenticels). Bark is reddish-brown. In the spring, the tree produces droopy spikes of flowers. Roundish fruits with lobes appear in the summer and open in the fall to reveal popcorn-like seeds.
