Houndstongue

What is houndstongue?

Houndstongue is a Eurasian biennial in the borage family, named for its long, soft leaves. Sound houndstongue identification relies on three features: velvety, tongue-shaped rosette leaves in year one, clusters of dull maroon flowers in year two, and hooked burs that grab anything brushing past. Those burs carry its seed far on livestock, pets and people.

Its biggest problem is poison. Its alkaloids cause liver damage in cattle and horses, and risk is highest when dried plants end up in hay. The burs also lower the value of wool, and on range and in forest openings the plant moves into disturbed, open ground at the expense of better forage.

Houndstongue identification: what to look for

Look for two forms. First-year plants are flat rosettes of large, soft leaves; second-year plants send up a hairy, branching stalk with small purplish flowers and then burs. Run a leaf between your fingers: it should feel softly hairy. Each spent flower leaves up to four flat, hooked nutlets.

• Rosette leaves: 4 to 12 inches long, 1 to 2 inches wide, smooth-edged, softly hairy, on stalks.
• Stems: A stout, coarse-haired stalk 1 to 4 feet tall in year two, branching near the top; leaves shrink and lose their stalks up the stem.
• Flowers: About 1/4 inch wide with five lobes, dull reddish-purple to burgundy, in clusters that unroll like a scorpion's tail.
• Burs: Four flat nutlets per flower, about 1/3 inch long, covered in barbed hooks.
• Taproot: Thick, black, woody and branching, often longer than 3 feet.

Where it grows in the United States

Houndstongue occurs throughout the lower 48 states except Florida, Louisiana, Mississippi, Oklahoma, South Carolina and Texas, and it is not reported in Alaska or Hawaii. It is a recognized problem in natural areas and parks in Michigan, Indiana, Missouri, Colorado and Oregon.

It grows on roadsides, logging roads, waste ground, heavily grazed pasture, disturbed woods, forest clearings and lake shores, and in the West in sagebrush, pinyon-juniper, aspen and ponderosa pine communities. It is most abundant where more than about a tenth of the ground is bare. It handles partial shade along forest edges as well as open meadows and moister grasslands, and grazing, logging and fire that expose soil give it a foothold.

Houndstongue look-alikes

A few plants get mixed up with it:

• Blueweed (Echium vulgare): Another borage-family biennial with hairy, narrow rosette leaves and nutlets in fours, but its hairs are stiff and bristly, its flowers open bright blue from reddish-purple buds, and its nutlets are small, angular and wrinkled.
• Common mullein (Verbascum thapsus): Also starts as a big first-year rosette, but its leaves are densely woolly and can reach about 20 inches, and the second-year stalk is usually a single, stout spike that can top 7 feet, with tightly packed flowers rather than branched clusters.
• Common burdock (Arctium minus): Another large-leaved rosette plant that ends up loaded with clinging burs, but burdock's leaves are heart-shaped and sit on hollow stalks, and each of its burs is a whole seed head forming a round, bristly ball. Houndstongue's leaves are tongue-shaped, and each flower leaves behind four separate, flat nutlets covered in barbed hooks.

How to get rid of houndstongue

Pulling, digging and mowing: Because the plant lives about two years and its seed is short-lived, manual control works well if you stop seeding. Dig or pull plants, taking as much taproot as possible, or cut rosettes 1 to 2 inches below the soil surface in fall or early spring; wear gloves. In northeastern Oregon, hand pulling cut a population by 85 percent. If plants are flowering, cut them at the base and bag stems that carry burs. Clipping second-year plants in late June kept about 60 percent from regrowing and dropped seed output from about 364 to 25 per plant. Shallow cultivation of young rosettes in fall or early spring also works.

Cultural control matters most, because the right conditions keep it from coming back.

• Reseed thin or bare areas with competitive grasses or native perennials, and adjust grazing timing and intensity so desirable plants stay dense.
• Do not use livestock to graze it down; the plant is toxic.
• No biological control agents are approved, so rely on prevention, digging and herbicides.
• After fire, logging or grading, check about a month later and again the next spring for rosettes, and reseed with certified weed-free seed.

Herbicides: Herbicides work best on rosettes and young, actively growing plants, and Washington's weed board strongly recommends a surfactant. Active ingredients reported to kill houndstongue include picloram, dicamba, chlorsulfuron, metsulfuron and 2,4-D amine; the best choice depends on growth stage, stand density and weather, and repeat treatments over several years may be needed to catch new seedlings. Choose a product labeled for your site (pasture, rangeland, forest, roadside or yard), follow grazing and haying restrictions, and remember the label is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Burs are the main way it travels, so pick them off pets, horses, gear and clothing before leaving infested ground, and clean equipment. Keep it out of hay fields so it never ends up in bales.

Watch trails, roadsides, logging roads and freshly disturbed or burned ground for rosettes, and remove plants before they flower. Because seed rarely lasts beyond two or three years, a few seasons of stopping seed can nearly clear a site.

Questions we get about houndstongue

Similar weeds

Common MulleinVerbascum thapsusCommon BurdockArctium minusBuffaloburSolanum rostratum