Controlling Invasive Plants in Forests
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.
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.
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.
Hedera helix (English Ivy)
Photo credit: Forest & Kim Starr, Starr Environmental, Bugwood.org
English ivy is a popular groundcover but it has spread beyond the garden and has overtaken forests, displacing native plant species across the United States. It forms both mats which cross the forest floor and woody vines which climb trees (up to 100'). These mats and vines block out sunlight, preventing native plant germination and killing trees. The plant spreads through runners and wildlife disperses its seeds.
In the shade, English ivy leaves are lobed (2 to 3 leaves per leaf), dark green with white veins, and waxy. In the sun, or on mature vines, the leaves can also be oval. Leaves are arranged alternately along the stem. Both groundcover and vines will produce clusters of small, dark purple fruits. During the summer, mature vines exposed to sun will also produce yellow flowers.
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.
Lygodium microphyllum (Old World Climbing Fern)
Fronds: non-reproductive on the left, reproductive on the right. Photo credit: Peggy Greb, USDA Agricultural Research Service, Bugwood.org
Old world climbing fern has aggressively invaded the wetlands and hammocks (hardwood forests with deep soils) of Florida and is threatening habitats in the Gulf States. It is considered a problem weed in North Carolina. The fronds of the fern can climb up to 90’ by twining around trees, shrubs, and across the ground. They can covers trees, and are especially a problem in bottomland swamp forests. Groups of leaflets (referred to as ‘pinnae’) grow from the frond oppositely arranged and are about 2 – 5” long. The pinnae are further subdivided into several pairs of leaflets (i.e., pinnules). The pinnules are fringed with rolled-up leaf tissue which covers the sori.
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.
Oplismenus hirtellus ssp. undulatifolius
(Wavyleaf Basketgrass)
Photo credit: Kerrie L. Kyde, Maryland Department of Natural Resources, Bugwood.org
Wavyleaf basketgrass forms dense mats under a deciduous forest canopy. The mats are so dense that native vegetation, including tree sprouts, cannot grow. It has been noticed in Maryland. There is a strong concern that it will become a serious problem in the southeast if nothing is done. Please watch out for wavyleaf basketgrass.
Wavyleaf basketgrass is a grass which trails along the ground by branching out at stem nodes. The leaf blades (½” wide, 1½ - 4” long) lie flat on the ground and are wavy, hence the name, and taper into a sharp tip. The leaf sheaths and stems are hairy. Its flowers bloom in the fall and have pointy tips. The seeds disperse by sticking to passing wildlife and people.
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.
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.
