Hound's-Tongue in British Columbia

Hound's-Tongue in British Columbia

hound's-tongue image

Hound's-tongue in flower
Photo: R. Needham

Hound's-tongue (Cynoglossum officinale) is a burred noxious weed found in forest rangelands and roadsides in the southern interior of B.C. This weed causes a loss of pasture and range for grazing animals, increases cattle marketing costs, and reduces fitness in livestock. In addition to being a general nuisance to recreationists, hound's-tongue also has the potential to poison domestic animals and wildlife that might graze on this plant.

Seeding of disturbed soils, use of integrated management techniques and public awareness will reduce spread and the negative impacts of this weed.

The Plant

Hound's-tongue is a biennial to short-lived perennial plant in the Borage family which flowers from May through July. This soft, hairy plant forms a low growing rosette of leaves in its first year and then bolts in the second year to form a plant 0.3 to 1 metre tall (1 to 3 feet). The common name for this weed results from the size and shape of the rosette leaves which resemble a dog's tongue. The dull reddish-purple flowers (1 cm wide) originating on the upper part of the stem produce four nutlets (seeds) each. These brown to greyish-brown seeds, rounded triangular in shape, are covered with short, hooked prickles. These burred seeds, which easily attach to passing animals, have contributed to the quick and widespread distribution of this weed in B.C.

rosette image

First year plant (rosette)
(Note: Leaf shape resembles a dog's tongue)

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Hound's-tongue seed
(Note: Hooked prickles on burred seed easily attach to passing animals)

Habitat and Distribution

Found on pastures, roadsides, meadows and forested areas in B.C., hound's-tongue easily colonizes and forms dense monocultures on disturbed habitats. This weed prefers forest sites and thrives especially well on openings in the forest cleared by logging operations and road construction. Hound's-tongue is quite shade tolerant and is not well adapted to drier grassland sites with under 30 cm annual precipitation. It does survive well in wetter grasslands and moist draws in the drier sites. Most infestations occur on coarse, gravelly to sandy soils.

Native to Eurasia, hounds-tongue is thought to have been introduced to North America in cereal seed. The earliest record of hound's-tongue in B.C. is from Keremeos, 1922 (Royal Provincial Museum). The weed is now widely distributed throughout the southern interior from the Empire Valley-Dog Creek area south through the Thompson-Nicola, Okanagan-Boundary and East Kootenay regions. It is estimated that in excess of 2,000 hectares (5,000 acres) are infested in British Columbia.

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Dense infestation in logged area

The Problem

Hound's-tongue produces more than 600 burred seeds per plant. When livestock are exposed to the plants, these seeds attach themselves to the animal, including the facial area which causes eye irritations. This problem, as well as the general cleaning of infested livestock prior to marketing, results in stress and possible weight loss.

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Burr infested cows

Not as significant a problem, but still a severe nuisance to recreationists, is the necessity to remove seeds that cling to clothing when hiking in infested areas.

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Hikers help spread the weed

Hound's-tongue contains large quantities of toxic pyrrolizidine alkaloids. Cattle and horse deaths have occurred in the U.S. and Russia from eating hound's-tongue contaminated hay. Few livestock have been observed eating green hound's-tongue in B.C., possibly discouraged by the distinctive odour of the plants. The leaves becomes more palatable when mature however, resulting in a potential poisoning hazard late in the season. Symptoms of poisoning would include weight loss, photosensitization, jaundice, diarrhea, nervousness, convulsions and coma.

Due to the troublesome nature of this weed it has been designated a Noxious Weed (B.C. Weed Control Act) in the North Okanagan, Thompson-Nicola, Columbia-Shuswap, Cariboo, Kootenay-Boundary and Okanagan-Similkameen Regional Districts.

Management

1. Prevention:

Don't let hound's-tongue go to seed. Hand pull isolated plants and small patches and remove as much of the root as possible. Cutting second year plants, by conventional mowing if practical or with mechanical "weed-eaters," greatly reduces seed production and spread potential. If cut close to the ground many plants will not regrow.
Seed disturbed or bare soil to a competitive perennial forage cover immediately after disturbance.
Clean burrs from animals and from clothing and shoes before leaving infested areas.

2. Chemical Control

Hound's-tongue can be controlled in the short term with selective herbicides such as Tordon 22K, Banvel and 2,4-D Amine. Tordon 22K applied in spring, summer or fall provides excellent control. Tordon cannot be used in forested areas or in logged areas prescribed for replanting. Tordon use is generally limited to roadsides, landings and to small patches on grassland pastures. Banvel and 2,4-D herbicides provide good short term control.
USE CAUTION WHEN APPLYING HERBICIDES AND READ THE LABEL BEFORE USE

3. Biological Control

British Columbia is committed to the use of natural agents to control noxious weeds. Use of natural agents which weaken hound's-tongue by feeding on various parts of the plant could provide long term, economical control when combined with other methods. Although no agents have yet been approved for release against hound's-tongue in North America, research is underway in Europe to find candidate agents which feed only on the target weed. To date, three promising insect agents have been found. The Province of B.C. and the B.C. Cattlemen's Association are sponsoring this research.

Co-published by:
The B.C. Ministry of Agriculture and Food
B.C. Cattlemen's Association

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