Invasive Species

An invasive species is any kind of living organism not native to a specific location. Invasives cause harm by outcompeting native species and eventually disrupting ecosystems.

According the the Minnesota Department of Natural Resources, a number of invasive species (such as zebra mussels, Eurasian watermilfoil, common buckthorn, and emerald ash borer) threaten the state's ecosystem. Managing invasive species and establishing native vegetation are goals of the City's Natural Resources Management Plan.

Managing Invasive Species


Buckthorn is a non-native shrub brought from Europe in the mid-1800s for use as a hedge or windbreak plant. It forms dense thickets and will out-compete native shrubs, tree seedlings, and perennials such as wildflowers for sunlight, water, and soil nutrients. Buckthorn became a restricted noxious weed in 2001 and can’t be purchased in Minnesota.

Common buckthorn and glossy buckthorn are the two species of interest. They can be easily identified because they leaf out earlier in the spring than most native plants and retain green leaves well into November. Berries have a laxative effect on birds and seeds are distributed widely each year. Seed can remain alive in the soil for more than six years.


Buckthorn can be removed by mechanical and chemical methods. Control will take several years and usually cannot be done in a single season. The most effective time for buckthorn removal and control is late summer through fall. Proper identification is important so that native shrubs, such as American plum, chokecherry, or grey dogwood, are not removed by mistake.

First remove the berry-producing plants. This can be done by cutting plants close to the base and covering stumps with cans or thick black bags to keep sunlight out. Stumps can also be treated with an herbicide (glyphosate or triclopyr) immediately after removal. Use rodeo brush herbicide or equivalent when working near water or wetlands. Always use chemicals in accordance with the law and the product label.

Buckthorn can also be pulled out of the ground with a weed wrench or by hand. Residents can borrow a wrench for up to seven days from the Physical Development Department.

Follow-up control, either by pulling or spraying with herbicide, in areas where you have previously removed buckthorn is necessary to keep the species from returning. Buckthorn seeds can remain viable in the soil for more than six years.

Weed Wrench Program

The City of Golden Valley has weed wrenches available for use by residents. They can be checked out for up to seven days and picked up in the Physical Development Department in the lower level of City Hall during office hours (Mon - Fri, 8 am - 4:30 pm). When borrowing a wrench, residents must leave their name, address, phone number, and a $100 security deposit, which will be returned when the wrench is checked in.

If you want to remove buckthorn on City property, check out this map showing where you can volunteer. Then fill out a volunteer form and email it to the assistant City forester.


Emerald Ash Borer

The Emerald Ash Borer (EAB) is an invasive beetle that attacks and kills ash trees. Its larvae kill ash trees by tunneling into the wood and feeding on the tree’s nutrients. Since its accidental introduction into North America, EAB has killed millions of ash trees in 35 states and the District of Columbia. With almost a billion ash trees in forests and urban areas, Minnesota is a prime target for EAB.

To prevent the spread of Emerald Ash Borer, a state quarantine is in place for Hennepin, Ramsey, and several other additional counties. This means any ash material (trees, logs, branches, chips, mulch, etc) and all hardwood (non-coniferous) firewood is not to be transported outside these quarantined counties. This material may enter the quarantined counties and travel within them; however, once inside the quarantine, it is not allowed to leave.

The metallic-green adult Emerald Ash Borer beetles are a half inch long and are active from May to September. Signs of EAB infestation include one-eighth-inch diameter D-shaped exit holes in ash tree bark and serpentine tunnels packed with sawdust under the bark.


Garlic Mustard

Garlic mustard is an aggressive biennial herbaceous (or herb) plant, which means it does not flower until its second year and then it dies. It grows in a way that crowds out native wildflowers, tree seedlings, and woodland plants and can totally dominate a woodland within five to seven years. This invasive plant species can be found throughout Golden Valley.


Garlic mustard can be managed by pulling up the second year plants before they flower and produce seeds, typically in early spring. Even though it is a prolific seed producer, garlic mustard can be managed by preventing seed production of plants over several years. Managing this species takes a strong commitment once it becomes established.

Garlic mustard in the Bassett Creek Nature Area

Because flowering garlic mustard can spread seeds even after it's been pulled up by the roots, the Minnesota Department of Agriculture (MDA) asks that you bag the plants in paper bags as you weed them. Bagged plants should dry thoroughly before disposal by burning, burying deeply in an area that will not be disturbed, or landfilling, according to the MDA.

If you want to remove garlic mustard on City property, fill out a volunteer form and email it to the assistant City forester.

Fun Fact: You can also use garlic mustard to make a tasty dish.


Gypsy Moth

Gypsy moths, from the butterfly and moth family, are considered by many experts to be the single most destructive pest of trees and shrubs. They were discovered in Golden Valley, St Louis Park, and Minneapolis in fall 2001. No more were found in the Twin Cities area since the Minnesota Department of Agriculture treated 1,850 acres in May 2002 until fall 2016, when an infestation site was found in Richfield and two other areas in east central and southeast Minnesota. those three sites were treated in June 2017 to eradicate and slow the spread of gypsy moths. At the same time, gypsy moths were found in the Lowry Hill area of Minneapolis. In 2019, areas in Lakeville, Stillwater, and Chisolm were treated to slow the spread of gypsy moths.

By 2014, Minnesota was mostly in the pre-infestation area. The Arrowhead region and a few counties in extreme southeastern Minnesota had areas where low-level moth populations were present. Lake and Cook Counties were designated a state and federal quarantine area in 2014 and remain quarantine areas. Populations had increased to a level where previous treatments were ineffective and other management strategies became necessary to contain the infestation. In other areas, targeted treatments are used to slow the spread of this pest. In northeastern states, the caterpillars have defoliated and destroyed whole forests, lowered property values, and required huge investments by governments for control.

Containing these invaders is not easy. Immobile but fertile female moths deposit eggs everywhere, including vehicles, camping equipment, etc. These tan egg masses spend most of the year waiting for a ride from unknowing creatures, including humans. When the eggs become larva (caterpillars) in May, they do major damage feeding day and night for about six weeks. Watch for their bright yellow heads and brown bodies lined with pairs of five blue and six red spots along the back. The adult male moth is medium-sized with brown wings and, unlike many moths, flies during the day. The female is generally white and does not move. If you see a white, flying moth, it is not gypsy moth.

If you see gypsy moths in any life stage or even suspect a gypsy moth infestation, report it immediately to 651-201-MOTH or 1-888-545-MOTH.

For more gypsy moth information, visit the Minnesota Department of Agriculture: Gypsy Moth