Green Horizons Newsletter - AgEBB

Green Horizons

Volume 9, Number 2
Spring 2005

Exotic Invasives: Missouri’s Unwanted Plants
Adapted from MDC Botanist Tim Smith’s article “Plants That Won’t Stay Put,” April 2001 Missouri Conservationist

Once in the forest canopy, the dense tangle of kudzu vines shades out ALL vegetation beneath it.
Think of any one of Missouri’s unique ecosystems as a precision watch. The numerous levers, springs and cogs in the watch fit together as a harmonious, functioning whole. Introducing exotic species can be compared to opening the back of the watch and throwing in some additional parts. They may stay out of the way and have no effect. They might cause it to run fast or slow. Or, the extra part may fall into just the right spot to stop the watch completely. An example of a “stoppedwatch” ecosystem might be a formerly diverse southern Missouri hardwood forest that has become completely covered by kudzu – an exotic vine – to the extent that only kudzu grows there.

For thousands of years, Missouri’s native plants have competed for available space, light, soil, water, and nutrients. Along with their natural enemies (insects and diseases) they have produced a precise natural world that is (or at least was) in balance. In the last few hundred years, a host of exotic plants have arrived here from all over the world and tilted the balance of the struggle.

Some exotic plants, also known as non-natives, were brought here intentionally and have not aggressively spread. Tulips, originally from Asia, are an example. They stay where we plant them and require special watering, fertilizing, and protection from the heat or cold to keep them healthy.

Other non-native plants, whether brought to the state by design or by accident, have spread so rapidly into native ecosystems due to the absence of their natural enemies that kept them in check back home that they out-compete and replace our native species. A few readily identifiable problem species are described below.

Autumn olive was widely planted in the past for food and cover for wildlife, windbreaks and erosion control. It can reach heights of 20 feet.
Autumn Olive (Elaeagnus umbellata). Native to China, Japan and Korea, autumn olive was widely planted in the past for food and cover for wildlife, windbreaks and erosion control. It can be found away from planting sites in old fields and pastures, along roadsides and in open forests. Capable of reaching heights up to 20’, it can easily choke out native forbs, grasses, shrubs and small trees.

Shrub or Bush Honeysuckles (Lonicera maackii and L. morrowii). In contrast to our native twining vine honeysuckles, these Asian species are shrubs. They have been planted as ornamentals and wildlife food plants, but now often replace native shrubs and eliminate woodland wildflowers from the forest floor. This completely changes the character of the forest understory to the detriment of native plants and animals.

Japanese Honeysuckle (Lonicera japonica). This climbing vine was brought from Japan in 1806 for use as ground cover. Now common over much of the eastern U.S., this exotic aggressively colonizes open or forested areas. It can completely cover shrubs and low-growing plants, producing dense shade that prohibits growth beneath it.

Kudzu (Pueraria lobata). Six inches a day is the documented growth rate of this vine. Kudzu was brought from Japan in the late 1800s and promoted as livestock forage and erosion control. More aggressive than Japanese honeysuckle, it spreads over the ground and climbs on anything. Once in the forest canopy, the dense tangle of vines shades out ALL vegetation beneath it. Its seeds can be dispersed over long distances further increasing its spread. Cold winters can limit kudzu, but cold-hardy plants have now been found along the northern tier of counties in the state.

Sericea Lespedeza can choke out native plant vegetation. Photo: Jim Rathert, Missouri Dept. of Conservation
Sericea lespedeza (Lespedeza cuneata). This perennial legume was brought from eastern Asia and has grown in Missouri sincethe 1930s for erosion control along roads and pond levees. Although not as palatable as native lespedezas, it is still promoted in the southeastern U.S. as livestock forage. In Missouri, this plant chokes out native vegetation found on prairies, glades, savannahs and gravel bars.

Purple Loosestrife is one of Missouri’s most noxious weeds and thrives in full sun.
Purple Loosestrife (Lythrum salicaria). This perennial plant was brought from Europe and Asia in the 1800s for use as an ornamentaland as a nectar source for honeybees. This species is so invasive that is has joined the likes of johnsongrass on Missouri’s noxious weed list. It has the ability to dominate freshwater marshes, wet prairies and other wetland habitats, completely eliminating wetland flora. It thrives in full sun, where a single plant can produce 300,000 tiny seeds in one season.

The following websites contain the latest information on invasive exotic plants in Missouri:. This site maintained by the Missouri Botanical Garden categorizes plants by their invasiveness and includes photos and links to the Missouri Vegetation Management Manual and other references. This Missouri This Missouri Department of Conservation site also links to the Manual and Missouri Conservationist articles on exotic species topics. The Nature Conservancy’s invasive weeds site contains photos and downloadable documents with control information for many U.S. weeds This site contains profiles and images of invasive species.

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