Allegheny River Headwaters Watershed Conservation Plan

Allegheny River Headwaters Conservation Plan
Chapter 4. Biological Resources
germinates from seed in the fall, then grows into a seedling over winter, and primarily flowers in the
spring. Seeds remain viable for two to five years in the seed bank.
Cheatgrass typically invades pasture lands and other open areas, as it has done in McKean County. It
crowds native species as it competes for resources, such as space, sunlight, and nutrients.
Manual, chemical, and biological control methods are effective in reducing populations of
cheatgrass. Control methods, such as fire, mowing, grazing, tillage, interseeding, and competitive native
species, are examples of manual techniques that have been used to effectively reduce populations of
cheatgrass. The use of herbicide, in addition to other control methods, increases the efficiency (USDA
Forest Service, 2005a).
Crownvetch
Introduced into the U.S. in 1950 for erosion control purposes, the Europe, Asia, and African native is
an herbaceous legume with creeping stems that can grow two to six feet long. It is used as a ground cover
in areas susceptible to erosion, such as road banks and right-of-ways, because of its rapid growth. It
spreads via seed dispersal and creeping root system. It has been known to invade woodland edges,
agricultural fields, pastures, hayfields, streambanks, and gravel bars. Populations of crown vetch have
been established in Potter County.
Manual and chemical control options are available. Prescribed burning that is conducted in late
spring and needs repeated annually for several years to effectively exhaust the seed bank. Mowing
conducted in late spring or multiple mowing sessions in June and late August—to correspond with
successive leaf-out periods—will reduce populations. Chemical control with herbicides can be applied in
early spring following instructions on the selected herbicide.
Garlic mustard
Native to Europe, garlic mustard was introduced to the U.S. in 1868, when it was cultivated for food
and medical use. It has been identified within Potter County, while no infestations within McKean County
have been detected.
This cool season biennial herb has stalked, triangular to heart-shaped, coarsely toothed leaves that,
when crushed, give off an odor of garlic. Garlic mustard can reach two to three and a half feet in height,
and produces button-like clusters of small white flowers, each with four petals in the shape of a cross. A
single plant can produce 1,000 seeds. The seeds are produced in erect, slender pods that, when mature,
become shiny black, beginning in May. By late June, the plants die, holding their seeds throughout the
summer. The seeds remain viable for five or more years. Identification is critical, because it resembles
several native species that grow alongside it, such as toothwarts, sweetcicely, and early saxifrage.
Garlic mustard crowds out native species by aggressively utilizing needed resources, such as light,
moisture, nutrients, soil, and space. This, in turn, affects wildlife, depriving them of the essential food
source the displaced native species provided.
For example, one rare insect species West Virginia white butterfly is suppressed by garlic mustard’s
dominating presence and destruction of toothwarts, native plants that serve as the primary food source and
habitat for West Virginia white caterpillars. Due to the lack of toothwarts, the West Virginia white lays its
eggs on the garlic mustard, which produces a chemical toxin that affects the eggs’ ability to hatch.
To effectively manage garlic mustard involves a long-term commitment. Management options
involve a combined effort of mechanical and chemical treatments, and vary depending on size of the
infestation. In small infestations and where desirable native species occur, manual removal is possible;
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