University of Vermont Extension System
Department of Plant and Soil Science

Invasive Perennials OH 65

Leonard P. Perry, Extension Professor

One disadvantage of some perennials is that they are invasive-- they spread where you don't want them and are difficult to control and keep in bounds. They may spread by roots as in the case of mints, or by seeds as in the case of Purple Loosestrife. Those spreading by roots can be useful if in a confined situation, or used in rough areas such as slopes to control erosion. In perennial beds, the root-spreaders can kill out less vigorous species and take over most the bed. Those spreading by seeds may be useful as with many field wildflowers, yet some such as the Purple Loosestrife colonize wet areas eventually destroying them and the wetland wildlife habitats. It's for this reason this plant and ones behaving similarly are banned from sale in many states.

The invasive nature of perennials is relative. Many on the following list may not even be hardy (cold or heat) in certain areas, and therefore not perennials nor problems in these areas. Or they may be hardy, but not vigorous or a problem, in many areas. Others, especially the root-spreaders, may be less or not invasive depending on factors such as culture and soil types. Those invading by seed may not be a problem in northern areas if the short growing season keeps them from going to seed (such as some silver grasses). The term "invasive" is itself relative. To some, this means any plant spreading at all. To me an invasive perennial is one which not only spreads but is quite vigorous and difficult to control. Those that spread, but can be controlled by yearly cultivating or dividing, I term either "spreading" or "aggressive" depending on how fast they spread.

Other than cultivating and dividing and weeding out seedlings, root-spreading perennials may be controlled by planting them in containers either in or on the ground. If in the ground, make sure roots do not exit the drain holes or go over the top. If desired to keep these perennials from year to year, they may need to be divided and repotted annually to keep them from dying out. Herbicides may also be used to control these, such as those that are systemic when sprayed on the plant. Even these may need several applications to provide control. Herbicides that act by merely burning back the foliage, such as some of the "organic" ones, are not very effective with vigorous perennials which merely resprout from the roots. If using any herbicide, read and follow all label directions.

The following list is only a beginning of some of the more common perennials listed as invasive by some, in some areas of the world. This list was based on suggestions by members of the perennial email list on the internet, with others based on trials in Vermont and articles or books. (For this list address, and more information on perennials, consult Perry's Perennial Pages at http://www.uvm.edu/~pass/perry/). Others, especially those that "self sow" once they go to seed, may be in this group as well. Some species or cultivars of a perennial may be invasive, and others not, so just because a genus is listed below don't assume all its members are invasive. Merely use this list as a "red flag" to check closer into a particular plant or genus of perennials keeping the above discussion in mind.

Return to Perry's Perennial Consumer Page

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. Lawrence Forcier, Director, UVM Extension System, Burlington, Vermont. University of Vermont Extension System and U.S. Department of Agriculture cooperating, offer education and employment to everyone, without regard to race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status.

Last reviewed 6/18/97