- Invasive trees and shrubs are non-native plants that can reduce property values, damage the environment and harm human health.
- Native woody plants also can be aggressive when they spread into areas where they are not wanted.
- Common woody invasive species in Minnesota:
Common aggressive woody plants
Some commonly seen invasive woody plants in Minnesota include:
- Amur maple
- Norway maple
- Non-native bush honeysuckles
- Multi-flora rose
- Black locust
- Japanese barberry
- Russian olive
- Siberian elm
- Siberian pea shrub
Native woody plants can also be aggressive growers and spread into areas they aren’t wanted. An example of this is encroachment of box elder and cottonwoods into lands planted as grasslands.
Native plants that grow rapidly include poison ivy, blackberry, raspberry, sumac, hazel, prickly ash, dogwood, wild grape, Virginia creeper and poplar species like aspen and cottonwoods.
Controlling woody plants
Non-chemical treatment options may vary with species and age of the woody plant.
Mechanical control methods
- Pulling. Removing the root crown by pulling is effective. Success depends on the species. Hand pulling tools are available.
- Frequent mowing or burning. Repeated mowing may kill woody broadleaf plants. Burning can be effective on some woody plants.
- Burning every 3 years in a grass CRP or native grass/forb planting is recommended. Larger stems will not be controlled with fire.
- Cut and cover stumps. Covering stumps with plastic or material that excludes light for two years can reduce sprouting.
- This can be effective on species that stump sprout. Not effective on species that sucker or spread from lateral roots.
- Grazing. Grazing livestock, particularly goats, in a concentrated area of plants will reduce foliage and stems in the area. Herbicide treatments may be necessary.
- Note: Livestock will also eat desirable trees and shrubs.
Equipment for controlling undesirable woody plants varies from inexpensive hand tools to large power equipment.
Select tools according to your budget, size of plants, number of plants, size of the site being managed and who will be doing the work.
While mowing or cutting can be used as a management strategy, most deciduous trees and shrubs will re-sprout after the trunk is cut. Some woody plants like aspen can resprout from underground lateral roots several feet from the main plant. These species must be controlled chemically for complete control.
Chemical control methods
- Cut stump treatment. Cut the plant near the ground and treat the cut surface (cambium or bark ring) immediately with a labeled herbicide.
- Remove any berries or reproductive cut stems by chipping, burning, or hauling to a brush dump.
- Note: Transporting cut stems may spread seeds or reproductive parts. Non-reproductive stems can be left in the woodland to help prevent erosion.
- It is illegal to transport certain invasive species. Check the Minnesota Department of Agriculture for specific information on getting rid of them.
- Low volume basal spray. Wet the bark area from ground level up to 12 to 15 inches. The bark should be wet but not dripping.
- Leaf application. May be used on seedlings, small plants and resprouting plants. Spray leaves to wet around the entire tree. Avoid spraying non-target plants.
Always read and follow label directions, wear recommended protective clothing and avoid contact with non-target plants. The label directions will list plants controlled, areas where the herbicide can be used and application methods.
Two common active ingredients found in brush killer herbicides are glyphosate and triclopyr.
- Glyphosate is a non-selective herbicide which can injure any green plant.
- Triclopyr is a selective herbicide active on broadleaf plants. Triclopyr has two formulations: amine (water base) and ester (oil base).
Before you purchase a brush herbicide, read the label to verify that the product is labeled for your site and will control the plants you want to eliminate.
Even after treatment with an herbicide, re-sprouting and seedling emergence may continue for years. Monitor sites for re-growth annually and retreat accordingly.
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
Many woody plants have multiple effective options for control. The Invasive Plant Control Database is a great resource for identifying control methods that fit your location, season, and even your level of expertise.
If you do not want to remove these woody plants yourself, you can hire contractors to treat and remove invasive plants. Find out more about how to hire a tree care professional.
The Minnesota DNR has more information on what to do about invasive species.
Re-establishing native vegetation
Many native species can re-establish from existing seed banks and roots if undesirable plants are controlled. Desirable plants can also be seeded or transplanted after controlling invasive species.
Planting grasses can reduce buckthorn seedlings while allowing desirable native species to establish. To prevent erosion, plant a grass mix of creeping red fescue, oats or Virginia wild rye after removing buckthorn.
Consider planting native shrubs such as high-bush cranberry, nannyberry, chokecherry, pagoda dogwood, gray dogwood, elderberry, American hazelnut and black chokeberry.
Cost share programs
There may be local, watershed, state or federal cost share programs available for landowners to control invasive species on their property and re-plant the treated area.
Contact your local Farm Service Agency (FSA), Natural Resources Conservation Service (NRCS) or Soil and Water Conservation District (SWCD) office for more details. Local conservation organizations may also support invasive species control projects.
Reviewed in 2020