Thursday, February 21, 2013
Anyone who spends time outdoors in Routt County probably has encountered the seeds of the houndstongue as hitchhikers on clothing, equipment, pets, horses, wildlife or livestock. Its facility for spread is what makes the Colorado List B noxious weed such a concern. A native of Europe and western Asia, houndstongue first was introduced to the U.S. as a contaminant in grain seed brought into Oregon in the 1890s and now has spread throughout many other states. It is distributed widely in Routt County and should be a concern to every landowner.
Cynoglossum officinale L. is a member of the Boraginaceae family and, therefore, is related to native bluebells. This biennial forb grows 1 to 3 feet tall, producing multiple racemes on multibranched stems. The 1/4-inch-long reddish-purple flowers produce four barbed nutlets per flower and as many as 2,000 per plant. The seeds germinate in spring and early summer and produce a rosette of leaves and a taproot as long as 3 feet. This stout taproot withdraws moisture from a depth that many of our native grasses cannot reach in a drought year like we experienced in 2012. Carbohydrates stored in the taproot during the first season of growth provide sufficient energy to produce flowers and seeds in the plant’s second year, even if the rosette leaves are removed late in the first season or the following spring. Any mechanical control must include cutting or pulling the weed at least 4 inches deep to remove the root crown and prevent the formation of the flowering shoot in the second year.
The name houndstongue comes from the resemblance of the leaves to a dog’s tongue. European folklore states that a leaf of houndstongue placed in a shoe will deter dog bites. There is a long history for the uses of houndstongue in European folk medicine for a variety of conditions. But the alkaloids that have contributed to its reputation as a medicinal plant also are responsible for the toxins known to cause irreversible liver damage in horses and cattle. The alkaloids produce a bitter flavor, which makes it unlikely that the plant will be grazed, but it might be eaten in a confinement situation if no other feed is available. The weed’s presence in hay (usually dryland) also presents a poisoning risk.
For small infestations — such as those that might occur along a trail or in a corral — digging, deep hoeing or pulling can provide effective control. Large and dispersed populations will require the use of herbicides — including 2,4-D (amine and ester), metsulfuron (Escort) and chlorsulfuron (Telar) — which are very effective when applied to fall (first year) and spring (second year) rosettes. Any of the herbicides need to be used with a nonionic surfactant to ensure good penetration of the pubescent leaves. All control measures need to include monitoring and follow-up treatments for a minimum of three years and should remain in place until the seed reserve in the soil is exhausted.
The Routt County Weed Program will present a houndstongue workshop March 26.
Gregory A. Brown is supervisor of the Routt County Weed Program. He can be reached at 970-870-5246 or email@example.com.