The Enemy - Houndstongue (Cynoglossum officinale) is a biennial plant that grows from 1 to 4 feet tall and reproducing by seed. Leaves are rough, long (resembles a hounds tongue), and somewhat hairy. The flowers of this enemy is reddish-purple and form to 4 prickly nutlets each about 1/3 inch long with barbs that allow it to cling onto clothing, fur, shoelaces, and anything that brushes against it. It was added to the Idaho weed list in January 2007. Houndstongue is toxic to animals as it causes liver damage. One of the ways that animals eat it is by indirect ingestion through weedy bailed hay and alfalfa.
The Strategy - It is mainly spread by wildlife and livestock, but we can find it anywhere humans have visited. The seed can catch a ride on an animals fur and carried for many, many miles. This plant is extremely mobile and once established out competes native habitat. It particularly gets dense in riparian (near water) areas as there is an abundance of moisture as well as it gets rubbed off animals by the branches. Because the seed is cased in the hard shell with barbs the seed can last 7 to 10 years in the soil.
The Defense - As this is an biennial plant, mechanical control can be quite effective. If you decide to ‘dig it’ out with a shovel just make sure that you get at least three inches of the root. We are having a difficult time trying to find an insect that is allowed in the country as this plant is in the borage family, and we have a few native borages that the insect like. Many herbicides are available that work well.
Opensight at 2.5 ounce/acre to rosettes. As plant bolts, increase the rate to 3.0 to 3.3 ounce/acre up to early bud stage. Add 1 quart of 2,4-D/acre after the bud stage. Click to view label.
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Telar® XP and Escort® XP are two that work extremely well. One positive about this treatment is that they will not be very harmful to range species such as Sagebrush and Buckbrush and you can spray in the spring summer or fall.
PLEASE NOTE -The proper use and application of herbicides can be an effective way to control and eradicate noxious and invasive plants. Before using herbicides, always carefully follow the label and safety instructions on the label. While we recommend the use of herbicides as one of the effective tools for integrated pest management, the Idaho Weed Awareness Campaign assumes no liability for herbicide applications.
For more information, click on the link below to download the Idaho's Noxious Weeds Control Guidelines publication produced by the University of Idaho Extension.
U of I Idaho's Noxious Weeds Control Guidelines (183 KB PDF download)