Buckthorn

There are two non-native species of Buckthorn shrubs thriving and spreading in Edina’s woodlots and other non-mowed areas throughout the City on public and private property. Common Buckthorn (Rhamnus cathartica) and Glossy Buckthorn (Rhamnus frangula) grow abundantly in woodlots, open meadows, along trails and streets, under specimen trees and other favorable sites.

For many years, these species have been used as hedge plants, most often in residential lots. They are native to northern Eurasia. They have been sold by the nursery industry at least since the nineteenth century. Recently, because of their extreme invasiveness, all species of buckthorn have been banned from sales. They have also been placed on the Minnesota State Restricted Noxious Weed List. Although sales are prohibited, it is not mandatory to remove.

The City of Edina recognizes the harmful effects of this shrub within the environments it inhabits. It displaces other more desirable plants, reduces beneficial and healthy biodiversity of flora and fauna, adds stress to trees through over-competition for nutrients, light and water, and grows in such thorny thickets that passage is very difficult.

The City encourages residents to remove buckthorn from their property. The City is actively removing Buckthorn on specific properties and is currently formulating a comprehensive buckthorn management plan for the parklands. The parks are being assessed and prioritized to determine how best to direct resources.

As previously stated, buckthorn can grow on almost any site that is not continually mowed. Buckthorn is spread by birds after eating berries of the female plants.

Buckthorn should not be cut without a further method of killing the stumps. If the stumps are not killed, they will re-sprout vigorously and be even more difficult to eradicate. Stumps can be chemically or mechanically neutralized or removed. Buckthorn uproots quite easily. A mechanical tool called a weed wrench can pull out shrubs up to 2.5” in diameter, 10 to 15 feet tall. The city has a limited number of these tools available to residents to borrow at not charge. Contact the City Forester about these tools. Some local hardware stores are also including this tool in their rental supplies.

If stumps are to be chemically treated, the most common method is applying glyphosate at 25 percent concentration to fresh cut stumps -- same day is most effective – but only from late summer through fall, as long as temperatures are above 32 degrees. Glyphosate is an active ingredient in Roundup and other brand name chemicals. Glyphosate cannot be used near waterways. When treating stumps around water, Rodeo is recommended.

Stumps can also be ground out with a stump chipper. They will not re-sprout.

Residents with buckthorn hedges who wish to remove them, but also need or desire the screening they provide, may want to formulate a gradual removal/replacement plan. Columnar Buckthorn is one variety that was widely used. This is a Glossy Buckthorn species. The seeds of this plant are spread as abundantly as other buckthorn species. They revert back to the natural form of Glossy Buckthorn.

Residential property that contains natural, wooded areas of varying sizes, who wish to remove the buckthorn should be aware of related concerns prior to formulating a removal plan. Distinguishing between buckthorn and other species is important, especially when the goal is to preserve and protect all other plants during a buckthorn removal operation. Not only will this help preserve the natural composition of the woods, but also the beneficial shade should reduce the amount of regeneration of buckthorn plants. Even though buckthorn is shade tolerant, it grows and reproduces best where more sunlight is available.

Treat wooded lots as sensitive areas. The naturally functioning processes are complex and the plants and trees have adjusted their growth accordingly. Too many disturbances can cause stresses which can lead to future declines or even mortalities among the plants that define your wood lot. Avoiding or minimizing soil compaction in these areas is very important. Soil compaction can adversely affect roots, which in turn adversely affects the visible vegetation. Overuse or abuse of chemicals is another concern. Over-reliance of chemicals throughout management plans could adversely affect the desired vegetation. In most instances, removing the existing buckthorn shrubs is only the beginning. Buckthorn seeds stay viable for six to eight years. A sound management plan must be long term. But it should also be devised in such a way as to minimize disturbances.

A potential restoration option in buckthorn infested areas is to replant with native plant materials. It is reasoned that native plants are naturally hardy and replanting may reduce the amount of buckthorn regeneration. This advice is best suited for small areas where economic, labor and future management considerations are feasible. In the highly competitive environment of natural wood lots, unless future care is provided, it is likely that a great quantity will not survive. Also, any plan devised will most likely detract from a more natural, successive woodland composition. Plant selection and spacing in natural areas, when determined through natural selection, abiding by laws known and unknown, would more likely render a woodlot healthier and more aesthetically pleasing than would an artificially designed site.

Residents who wish to receive further information on this subject may contact the City Forester Tom Horwath at 952-826-0308.