Controlling Invasive Plants 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
Alliaria petiolata (Garlic Mustard)
Photo credit: Chris Evans, River to River CWMA, Bugwood.org
Garlic Mustard was introduced in the 1800s for medicinal purposes and for cooking. Now, it is widely dispersed throughout the country and can be found in all parts of the state. The wildflowers in the mountains are most threatened by Garlic Mustard as it is shade tolerant and can compete with the flowers for the same habitat in woodlands. It also produces allelopathic compounds which inhibit the germination of other species' seeds. Humans and wildlife are most responsible for long-distance seed dispersal.
During its first year, the plant forms rosettes of kidney-shaped leaves. In its second year, it grows heart-shaped leaves (2 - 3") with deeply serrated edges. It will also produce a tall stalk (1 - 4') with small white flowers in spring. Flowers have 4 petals and grow in clusters. Seed pods are long, slender, and green and have shiny black seeds. The plant is distinguished by a slender white taproot and a garlic odor when stems and leaves are crushed.
Cyperus entrerianus (Deep-rooted Sedge)
Photo credit: Richard Carter, Valdosta State University, Bugwood.org
Deep-rooted sedge invades wetlands and disturbed areas throughout the southeastern United States. It grows in clumps which can reach up to 40” tall. It forms a thick mat of rhizomes. The leaves are glossy and flat or V-shaped. The terminal inflorescence has 5-11 rays which end in densely clustered spikelets.
Glechoma hederacea (Ground Ivy)
Photo credits (left to right): Leslie J. Mehrhoff, University of Connecticut, Bugwood.org; Richard Old, XID Services, Inc., Bugwood.org
Ground ivy was introduced for its medicinal properties and since has spread into moist forests and along streams in the eastern and northern United States. It spreads mostly from its stems, but also through seeds.
Ground ivy creeps along the ground, covering it with round or kidney-shaped round-serrated leaves (1 – 3” diameter). They are arranged oppositely along the stem. It is from the Mint family so leaves release a mint odor when crushed. And, like other mints, the stems are square. Blue violet flowers whorl around the leaf axils; these bloom in early spring.
Heracleum mantegazzianum (Giant Hogweed)
Photo credits (left to right): Terry English, USDA APHIS PPQ, Bugwood.org; Thomas B. Denholm, New Jersey Department of Agriculture, Bugwood.org
Giant hogweed has only been reported in Caldwell County, North Carolina but it has caused problems in both the northeast and the Pacific Northwest and is listed as a federal noxious weed. The plant’s sap is poisonous and can cause severe burns and blindness. It also produces a dense canopy which shades out native species. One plant produces many seeds which are dispersed by wind and water. It commonly invades open areas with moist disturbed soils, such as those in fields, along stream banks, roadsides, and ditches. It is much easier to control an invasive species if we can manage infestations when they are still small. So, please watch out for giant hogweed and report any infestations to the N.C. Department of Agriculture and Consumer Services Weed Specialist at 1-800-206-9333.
Giant hogweed is a massive plant; it usually only lives for 2 years but it can grow to a height of 15’ and has enormous leaves and flower clusters. The large flat cluster, umbel, of small white flowers is reminiscent of Queen Anne’s Lace, but giant hogweed’s umbel is much larger, growing up to 2½’ in diameter. It blooms in midsummer. Its leaves are compound and arranged alternately along the stem. Each leaf is made up of 3 deeply incised leaflets which can grow as large as 5’ wide. The leaflets near the top of the stem are less incised and not as large. The stems are ridged, hollow and have purple spots on them. Fine white hairs grow at the nodes in the stem.
It is important to wear protective clothing and eyewear when removing this plant!
Giant hogweed is a massive plant; it usually only lives for 2 years but it can grow to a height of 15’ and has enormous leaves and flower clusters. The large flat cluster, umbel, of small white flowers is reminiscent of Queen Anne’s Lace, but giant hogweed’s umbel is much larger, growing up to 2½’ in diameter. It blooms in midsummer. Its leaves are compound and arranged alternately along the stem. Each leaf is made up of 3 deeply incised leaflets which can grow as large as 5’ wide. The leaflets near the top of the stem are less incised and not as large. The stems are ridged, hollow and have purple spots on them. Fine white hairs grow at the nodes in the stem.
It is important to wear protective clothing and eyewear when removing this plant!
Imperata cylindrica (Cogon Grass)
Photo credit: James H. Miller, USDA Forest Service, Bugwood.org
Cogon grass was accidentally introduced in the 1900s in packing materials; it has spread throughout the southeast. As of 2010, cogon grass infestations are not reported in North Carolina but it is in South Carolinian counties bordering the state and is very likely to find its way over the state line. The seeds of cogon grass are fluffy, reminiscent of dandelion seeds, and are easily dispersed through wind. It is much easier to control an invasive species if we can manage infestations when they are still small. Cogon grass is considered one of the world’s worst weeds. So, please watch out for cogon grass and report infestations to the N.C. Department of Agriculture and Consumer Services Weed Specialist at 1-800-206-9333.
Cogon grass grows in dense bunches which can form monotypic mats that can be as high as 6’ tall. Cogon grass is easy to identify in the spring, when its characteristic cottony, cylindrical seed head (2 – 8” long) blooms. It leaves are also fairly easy to identify because the midrib of the leaf is white and off-center. Leaves can be up to 6’ long and are about 1” wide, and taper to sharp points. The leaf margins are finely toothed. Leaves can turn reddish in the fall. Rhizomes form dense mats in the first foot of soil. The rhizomes have sharp tips.
Lespedeza cuneata (Chinese Lespedeza)
Photo credits (left to right): Dan Tenaglia, Missouriplants.com, Bugwood.org; James H. Miller, USDA Forest Service, Bugwood.org
Chinese lespedeza was introduced as forage but was found to be too tough and nasty-tasting for wildlife and livestock. Since then it has spread all over the eastern and midwestern United States. In North Carolina, it thrives in open habitats: meadows, open woodlands, fields, pond edges, roadsides, etc.
It grows to 2 - 5' in height on woody stems with numerous straight branches. It can be identified by its wedge-shaped leaf bases on its leaflets. Leaves grow in groups of 3, which are arranged alternatively along the stem. It blooms from July to October. Its flowers are white with violet throats.
It grows to 2 - 5' in height on woody stems with numerous straight branches. It can be identified by its wedge-shaped leaf bases on its leaflets. Leaves grow in groups of 3, which are arranged alternatively along the stem. It blooms from July to October. Its flowers are white with violet throats.
Lythrum salicaria (Purple Loosestrife)
Photo credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Purple loosestrife has aggressively invaded freshwater and tidal wetland habitats in the northeast and has been found in the northwestern mountains in North Carolina. It is much easier to control an invasive species if we can manage infestations when they are still small. So, please watch out for purple loosestrife and report any infestations outside of Forsyth or Watauga counties to the N.C. Department of Agriculture and Consumer Services Weed Specialist at 1-800-206-9333.
Purple loosestrife produces beautiful spikes of magenta flowers throughout the summer. The plant can grow as tall as 10’ but average height is 5’. The leaves are lance-shaped (less than ¼” long) and arranged either oppositely along the stem or in whorls of 3. Stems are covered in fine hairs and are square.
Microstegium vimineum (Japanese Stilt Grass)
Photo credits: Ted Bodner, Southern Weed Science Society, Bugwood.org;
seedhead photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Japanese stilt grass has spread throughout the southeast and is found all over North Carolina. It is shade-tolerant and can grow in full sunlight, so it is found in forests, lawns, along roads, especially in floodplains. Once introduced to an area (dispersal via animals, water, and people), it forms monotypic stands within a few years.
The grass grows 2 - 3' in height, with long, alternating lance-shaped leaves (1 - 3") with off-center midribs. The stalks are distinguished by nodes. Flowers are placed on spikes which grow from leaf axils and from the apex of the grass stem.
The grass grows 2 - 3' in height, with long, alternating lance-shaped leaves (1 - 3") with off-center midribs. The stalks are distinguished by nodes. Flowers are placed on spikes which grow from leaf axils and from the apex of the grass stem.
Miscanthus sinensis (Chinese Silvergrass)
Photo credit: James H. Miller, USDA Forest Service, Bugwood.org
Chinese silvergrass was introduced as an ornamental grass and escaped cultivation. It now has invaded habitats all over the United States and in western North Carolina. Besides being an aggressive competitor with native species, it is also a problem because it poses a fire risk.
This grass is highly distinctive. It grows in tall bunches (5 - 12') which produce a fan-shaped panicle which has a silvery pink inflorescence in late summer, early fall. The leaves are long (18") and have sharp points and silvery midribs.
Phragmites australis (Common Reed)
Photo credits (from left to right): Leslie J. Mehrhoff, University of Connecticut, Bugwood.org; Richard Old, XID Services, Inc., Bugwood.org
Common reed, the non-native variety, is ubiquitous throughout wetland habitats in North America. Once established it forms dense monotypic mats which preclude establishment and growth of native species. These mats of common reed not only decrease biodiversity but also decrease wetlands’ capacity to function effectively. It is dispersed by both seeds and rhizome fragments. The native variety looks very similar but it will not form the dense mats that the exotic does.
Common reed can grow as tall as 15’. Its leaves (6 - 24” long and 0.5 – 2” wide) are hairless and taper to a point; they are arranged alternately along the stem. Common reed stems are cane-like and green in the growing season and tan in the winter. It produces a plume of grayish purple inflorescence (5 – 16”) from mid-summer through fall.
Common reed can grow as tall as 15’. Its leaves (6 - 24” long and 0.5 – 2” wide) are hairless and taper to a point; they are arranged alternately along the stem. Common reed stems are cane-like and green in the growing season and tan in the winter. It produces a plume of grayish purple inflorescence (5 – 16”) from mid-summer through fall.
Phyllostachys aurea (Golden Bamboo)
Photo credit: James R. Allison, Georgia Department of Natural Resources, Bugwood.org
Golden bamboo has dispersed throughout the southeast, including in North Carolina. It is most common in moist, open forests. It spreads through rhizomes and forms dense thickets.
Golden bamboo is a woody grass that can grow as high as 30’. The stems are hollow (1 – 6” diameter) and green or yellow. Leaves grow in clusters (2 – 3” long), are lance-shaped and alternately arranged on the stem.
Solanum viarum (Tropical Soda Apple)
Photo credit: Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org
Tropical soda apple is an aggressive invader and in North Carolina its presence has been reported in fields used to hold cattle. It is much easier to control an invasive species if we can manage infestations when they are still small. So, please watch out for tropical soda apple and report infestations to the N.C. Department of Agriculture and Consumer Services Weed Specialist at 1-800-206-9333.
Tropical soda apple grows as a shrubby herbaceous plant that can grow as high as 6’. The plant’s stems and leaves are covered in prickles. It is distinguished by its small (1” diameter) watermelon-like fruits which appear in the summer. Young fruits are greenish and mottled; ripe fruits are bright yellow. During the summer, the plant also produces small white flowers with 5 petals. The leaves (4 – 8” long and 2.5 – 6” wide) are reminiscent of oak leaves – deeply lobed. They are arranged alternately along the stem.
Tropical soda apple grows as a shrubby herbaceous plant that can grow as high as 6’. The plant’s stems and leaves are covered in prickles. It is distinguished by its small (1” diameter) watermelon-like fruits which appear in the summer. Young fruits are greenish and mottled; ripe fruits are bright yellow. During the summer, the plant also produces small white flowers with 5 petals. The leaves (4 – 8” long and 2.5 – 6” wide) are reminiscent of oak leaves – deeply lobed. They are arranged alternately along the stem.
Sorghum halepense (Johnson Grass)
Photo credit: Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org
Johnson grass was introduced for forage and since has spread into open habitats throughout the United States. Its seeds can disperse through wind, water, animals, and contaminated grains and seeds. It can also regenerate from rhizome fragments. It spreads through its rhizomes so that it forms dense monotypic stands of grass.
Johnson grass grows to 8’. Stems are reddish near the base. Leaves are long (2’), smooth, and arranged alternately along the stem. The midrib of the leaf is white. The purple flower plumes bloom in the summer.
Tribulus terrestris (Puncturevine)
Photo credits: (plant) Richard Old, XID Services, Inc., Bugwood.org; (burrs) Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
Puncturevine is has invaded most of the United States but is only found in New Hanover and Durham counties in North Carolina. It is much easier to control an invasive species if we can manage infestations when they are still small. So, please watch out for puncturevine and report any infestations outside of Durham or New Hanover counties to the N.C. Department of Agriculture and Consumer Services Weed Specialist at 1-800-206-9333.
Puncturevine forms mats which can grow as wide as 4’ across. During the summer, the plant produces small yellow flowers with 5 petals. A week after flowering, the fruits appear. The fruits produce small woody burrs with sharp thorns, sometimes the burrs almost look like goat heads. The leaves are compound with tiny leaflets (less than ¼” long).
Puncturevine forms mats which can grow as wide as 4’ across. During the summer, the plant produces small yellow flowers with 5 petals. A week after flowering, the fruits appear. The fruits produce small woody burrs with sharp thorns, sometimes the burrs almost look like goat heads. The leaves are compound with tiny leaflets (less than ¼” long).
