Invasive Species - Amur Honeysuckle
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Honeysuckle can form a dense understory thicket which can restrict native plant growth and tree seedling establishment.
Honeysuckle Flowers

Native Origin: Native to eastern Asia; introduced into North America in 1896 for use as ornamentals, for wildlife cover and for soil erosion control.

Description: An erect multi-stemmed erect deciduous shrub with arching branches that grows up to 30 feet tall. The leaves are opposite, simple, ovate, 2 to 3 inches long, green above, paler and slightly fuzzy below. Fragrant flowers are tubular with very thin petals and appear in late spring. They are white changing to yellow and 3/4 to 1 inch in length. Abundant red berries, 1/4 inch in diameter, appear in late summer and often persist throughout winter. The stems are hollow with stringy tan bark. It reproduces both vegetatively and by seeds.

Habitat: Amur Honeysuckle can grow in a wide range of soil types. It tolerates wet soils for brief periods of time, such as at the edge of streams and creek banks that occasionally overflow. It can grow in full sun or full shade and can be found in fencerows, thickets, woodlands, roadsides, pastures, old fields, neglected areas and lawns. It is tolerate of all types of pollution, and thrives on neglect, tolerating severe summer droughts and cold winter temperatures with minimal dieback. It readily grows in zones 3 to 8.

Ecological Impacts: In forests the plant can adversely affect populations of native members of the community. It can spread rapidly due to the seeds being dispersed by birds and mammals. It can form a dense understory thicket which can restrict native plant growth and tree seedling establishment.

Toxicity: Berries may be mildly poisonous if eaten.

Control and Management:
Manual- Hand removal of seedlings or small plants may be useful for light infestations. Repeated clipping yearly to prevent dense stands from forming.

• Chemical- Use a systemic herbicide. Thoroughly wet all leaves with glyphosate (e.g., Roundup) as a 2- percent solution in water with a surfactant from August to October. Cut large stems and immediately treat stumps with imazapyr as a 10 percent solution or a glyphosate herbicide as a 20-percent solution. Check label directions for details. Contact your state coop extension for local recommendations.

• Prescribed burning- Initiate prescribed burning prior to the seed dispersal period (late summer to early autumn) to minimize reinvasion of treated habitats.

Amur Honeysuckle is a big problem at DuPage County, Illinois Forest Preserves.
Photo: © Red Planet Inc.

Trends and rising threats from invasive species
Humans intentionally and unintentionally spread invasive species. The foundations of agriculture and animal husbandry are based on ancient habits of selectively favoring some plant and animal species and their habitats over others for food, fiber, and medicine (Flannery 1973). According to Pimentel and others (1999), about 50,000 non-native species have been introduced in the United States. Many nonnative species have been deliberately introduced for erosion control (kudzu), food animals and fish (brown trout), agricultural crops (Johnson grass), and ornamental trees and landscape plants (purple loosestrife). Some insects and diseases have been introduced in ignorance, as was the Gypsy Moth, or as the unintentional result of a global economy, as with the West Nile virus and Zebra mussels (Pimental and others 1999). Many invasive plants in the United States were originally introduced for food, fiber or erosion control, or as ornamentals. For example, purple loosestrife was introduced as an ornamental in the early 19th century. Loosestrife is present in riparian areas throughout the continental United States and control costs are an estimated $45 million per year. Riparian areas are extremely valuable to native plants and animals, and the wholesale invasion by Loosestrife poses a serious threat of eventual extinction to numerous riparian-dependent species (Pimentel and others 1999).

Other plant species, such as European Cheatgrass, have almost entirely displaced sagebrush-grassland plants and associated animals. Cheatgrass has also seriously altered the fire regime from an average return interval of 60-110 years to 0-3 years. Cheatgrass is an example of the adverse impacts an introduced species can have on the environment. Some scientists estimate that Cheatgrass is present on 100 million acres of grassland-steppe in the western United States. Cheatgrass forms a dense, uniform carpet that out-competes native grasses and shrubs. It greens quickly, dries quickly and produces a very flammable cover that often burns completely, without allowing native plants to reestablish. In pinyon-juniper woodlands, the combination of Cheatgrass and fire may effectively prevent the re-establishment of the original woodlands (Mitchell 2000).

Invasive Species on National Forests / Invasive Plants
The United States has about 2,000 non-native invasive plant species, which are concentrated in California, Florida, and Hawaii (Mitchell 2000). On non-croplands in the midwestern states, one Forest Service researcher estimates that 14 percent of the plant species are non-native invasive plants. Trend data from the 19th century to the present indicates a significant escalation in the percentages of non-native invasive plants in the last half of the 20th century (Mitchell 2000). An estimated 3.5 million acres of National Forest System lands are infested with invasive weeds, according to the 2000 RPA assessment, which summarized local estimates from individual national forests (USDA Forest Service 2001). However, local estimates vary widely, and the agency lacks a comprehensive inventory for either terrestrial (land) or aquatic areas infested with invasive species. The Framework for Invasive Species calls for expanding inventory and monitoring activities to identify more invasive insects, pathogens and plants (Forest Service 2003).
Some species of particular concern to Forest Service managers are leafy spurge, knapweeds and star thistles, saltcedar, non-indigenous thistles, purple loosestrife, and cheatgrass in the West and garlic mustard, kudzu, Japanese knotweed, Tree-of-heaven, and purple loosestrife and hydrilla in the East (Mitchell 2000).

Insect Damage and Disease
Insect damage and plant disease are natural disturbances that are part of a healthy, functioning ecosystem, along with fire and wind damage. However, both native and non-native insects and diseases have caused above normal mortality rates on forested lands in the United States. Some 58 million acres or 8 percent of forested land are at risk for mortality rates that exceed the norm by 25 percent or more (USDA Forest Service 2001). High mortality rates can accelerate the development of high fuel-loading in fire-dependent forests, effectively remove important ecosystem elements, and reduce private property values. The highest profile exotic insects and diseases include Asian Longhorn Beetle, Emerald ash borer, Dutch elm disease, chestnut blight, white pine blister rust, Port-Orford cedar root disease, European gypsy moth, hemlock wooly adelgid, and beech bark disease. Aside from the potential economic loss from timber volume, many wildlife and fish species are dependent on the ecosystems affected by these invasive insects and diseases (USDA Forest Service, 2001).

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Family Ulmaceae - Zelkovas, Hackberries and Elms
There are about 200 species of trees and shrubs in Ulmaceae. 14 trees and 2 shrubs are native to North America. The Morton Arboretum is one of the largest living Ulmus collections in the world.(more than 30 species, in addition to numerous infraspecific taxa, hybrids, and cultivars).
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