Growing unnoticed at first, invasive species spread and cover the landscape. They change the ecology of the area, affecting wildlife communities including birds, wildflowers, native insects and even the soil. Over time, invasive plant species form a monoculture in which the only plant growing is the invasive plant.
Invasive species seem to have "super powers" that alter the ecological balance of natural communities. They flourish because controls in their native lands do not exist here. The Nature Conservancy ranks invasive species as the second leading cause of species extinction worldwide.
Native wildlife depends on native plants for food and shelter, and our natural heritage is tied to intact natural communities. Thus, controlling invasive species is important not only to humans, but wildlife as well.
Negative Effects of Invasives
Changes in the hydrology - wetlands dry out; release of chemicals into the soil that inhibit the growth of other plants (known as Allelopathy); changes in the soil; interruption of native species' reproduction; native plants and animals displaced; can be toxic to livestock; can cause dermatitis; limits recreational use of land and water; stops forest regeneration; impacts aesthetics; and dimishes biodiversity.
Invasive species are controlled by several management techniques, including early detection, monitoring, mechanical removal, herbicides, biological controls (agents that are natural enemies of the invasive species i.e. insects, bacteria, etc.), livestock grazing and prescribed burns. The management method used depends on the species being controlled.
Oakland County Offenders
Black Swallow-wort (Cynanchum louiseae) and Pale Swallow-wort (Cynanchum rossicum)
ID: Both plants have similar characteristics. Swallow-wort is related to milkweed. Details
Garlic Mustard -
ID: Herbaceous biennial plant with simple, toothed, triangular shaped leaves. Leaves form a basal rosette in the first year. In the second year, small white flowers appear on 3 ft. stems from basal rosette. Individual plants can produce 350 - 7,900 seeds. All parts of the plant when crushed have a garlic odor. Details
Phragmites, a.k.a Common Reed - Phragmites australis subspecies australis
ID: Tall perennial grass 6-15 ft. high that grows in wetlands. Plants form dense colonies with plume-like seed heads. Plants can produce as many as 2,000 seeds annually. Spreads from underground rhizomes (horizontal roots). Native species Phragmites subspecies americanus has shiny, reddish lower stems. Americanus has scattered stems and does not form dense colonies.
Country of Origin: Native to Europe and Asia, this invasive subspecies was introduced from packing material in ship ballasts and discarded in coastal marshes in the 1900s.
Ecological Threat: The invasive subspecies is widespread along coastal shorelines and wetlands. Degrading wetlands by displacing native plants and animals, this plant also reduces property value by blocking shoreline views. This dry plant material is a fire hazard. Permits from the Michigan Department of Environmental Quality are required for removal; visit the MDEQ's Aquatic Nuisance Control website for details.
Seasonal Solution: Management and control of phragmites involves herbicides, water control and mechanical removal. In most cases, permits from the Michigan Department of Environmental Quality are required. Visit the MDEQ's Aquatic Nusiance Control website: www.michigan.gov/deginlandlakes for more information. Large dense stands may require treatment by commerical applicators. Selecting the proper herbicide minimizes the adverse impact on water and native wildlife. Treatment in late summer or fall is most effective. Some control can be achieved by flooding cut stems during the growing season. Digging the plant only stimulates its spread. Ongoing monitoring is required.
Autumn Olive -
ID: A deciduous shrub 20 ft high and 30 ft wide with thorny branches. Simple gray-green oblong leaves have silvery scale under each leaf. Small light yellow fragrant flowers bloom April through June. Flowers produce red speckled round fruit (drupe) in September.
Country of Origin: Native to China, Korea, and Japan, this shrub was introduced into North America in 1830. Autumn Olive was once planted for wildlife food and cover.
Ecological Threat: This shrub grows rapidly and bears fruit in 3 to 5 years. Each shrub can produce 2-8 pounds of seed annually. The number of seeds per pound ranges from 20,000 - 54, 000! Seeds are widely dispersed by birds and have a high germination rate. It is highly adaptable and grows in drought conditions. Due to its nitrogen fixing capabilities, this shrub changes the nitrogen cycle in the soil affecting unique native plant communities.
Seasonal Solutions: Monitoring is necessary close to natural areas. Herbicide application is done to avoid damage to native species. Basal stem injections known as "drill and fill" are effective when the plant is dormant. Cutting stems without the use of herbicide only stimulates resprouting.
Common Buckthorn - Rhamnus cathartica and Glossy Buckthorn - Frangula alnus
These invasive species belong to the same family and cause similar problems.
ID: Small deciduous trees growing 6 m (20 ft.) tall. Simple leaves are oval. Common Buckthorn leaves have small teeth along the leaf edge while Glossy Buckthorn leaves have smooth edges. Common Buckthorn twigs have thorn tips. Barks are dotted in light-colored spots called lenticels. Exposed bark reveals orange sapwood and pink/orange heartwood. Small greenish flowers produce berries that turn dark purple when ripe in August/September.
Country of Origin: Native to Eurasia. Introduced into North America for fencerows and wildlife habitat.
Ecological Threat: Forms dense thickets that crowd and shade out native species impacts forest regeneration by preventing seedlings from growing. In fire adapted communities, buckthorn prohibits fire. Buckthorn changes nutrient cycling and also serves as alternate host for oat rust.
Seasonal Solution: Mechanical and chemical measures help control buckthorn; proper timing of herbicides to avoid killing desirable plants is paramount. Hand pulling is effective with small plants before seeds appear. Cutting without using herbicides only causes resprouting. Prescribed fire can control young seedlings if enough fuel is present in fire adapted communities.
- Two members of the Michigan Native Plant Producers Association are located in Oakland County. These local producers can provide additional information about the importance of using native plants.
- American Roots
- Wildflowers and native plants, many of Oakland County genotype.
- Phone: 248 627-8525 or 248 882-7768
- Oakland Wildflower Farm
- Michigan native forbs and grasses-specializing in Southeast Michigan genotypes.
- Phone: 248 969-6904