Weed of the Month: Flowers mask aggressive invader

During summer months, Sanders County residents may notice plants with attractive blue flowers along roads and disturbed sites. These flowers can fool people into overlooking an aggressive, invasive plant: Blueweed.

Blueweed's appealing flowers often lead people to consider it a desirable plant, and it is sometimes mistaken for lupine, chicory, or penstemon. Far from being desirable, this invasive species is toxic to livestock, is a skin irritant for people, and out-competes native plants that are important to wildlife. It is a priority weed to contain and eradicate in Montana and surrounding states.

Native to Asia and southern Europe, blueweed is a member of the Boraginaceae plant family (the same family as houndstongue). It is a taproot biennial that can reach heights of three feet or more and drop more than 2000 seeds, which are easily carried by water, wind, vehicles, humans, and animals. Blueweed is often seen along roads and trails, in pastures, hayfields, rangeland, and adjacent forest lands. Once established, it is difficult to control.

Plants first appear as rosettes in early summer. One or more erect flowering stems grow from the rosette, featuring funnel-shaped blue flowers with pink or red stamens. Stems and leaves are covered with hairs that can irritate skin, and stems will appear spotted.

The best time to control blueweed is when plants are in the rosette stage, before flowering stems appear. Hand pulling plants or digging them up with a shovel is effective at this stage. (Wear gloves and long sleeves to avoid skin irritation from the hairs on stems and leaves.) Herbicide treatment is also effective at the rosette stage. Control becomes more difficult once the plants begin to flower, and landowners are likely to find themselves with an increasing problem each year.

Are you wondering if that plant with the pretty blue flowers growing under your mailbox is blueweed? An online search with the terms "blueweed" and "Montana" will return helpful information from the Montana State University Extension Office, Montana Weed Control Association, Montana Department of Agriculture, Natural Resources Conservation Service (NRCS), and others. The Sanders County Weed District can help landowners confirm the weed's presence and offers herbicides and spray equipment at reduced rates to county residents. For information, contact the Weed District Office at (406) 826-3487 or email [email protected].