Summit Outside: Pretty, but invasive | SummitDaily.com
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Summit Outside: Pretty, but invasive

Dr. Joanne Stolen
Special to the Daily
Special to the Daily/Joanne Stolen
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What a funny name toadflax is? The name toadflax is thought to result from a mistake. It seems that the common toadflax may have been used to treat ‘buboes’ (boils) and was known as bubinio, meaning ‘toad,’ and from then on the plant became associated with toads.

The genus name linaria refers to the general similarity of the leaves of species to those of flax. They are also known brideweed, bridewort, butter and eggs, butter haycocks, bread and butter, bunny haycocks, bunny mouths, calf’s snout, continental weed, dead men’s bones, devil’s flax, devil’s flower, doggies, dragon bushes, eggs and bacon, eggs and butter, false flax, flaxweed, fluellen, gallweed, gallwort, impudent lawyer, Jacob’s ladder, mouth, monkey flower, North American ramsted, rabbit flower, rancid, ransted, snapdragon, wild flax, wild snapdragon, wild tobacco, yellow rod and yellow toadflax. Now that’s a lot of names! The term butter and eggs comes from the color of the flower: yellow resembles butter, and the orange resembles egg yolks.

Toadflax have been listed as a nuisance plant or “Weed of the Week” and included in the website invasive.org. Yellow toadflax is designated as a “List B” species in the Colorado Noxious Weed Act. It is required to be eradicated, contained or suppressed depending on the local infestations. As pretty as they are, they are not good for the environment.



We see them frequently in Summit County. In Colorado, these weed species are found at elevations from 5,000 feet to over 10,000 feet. Yellow toadflax in particular has spread into high mountain valleys and parks. Yellow toadflax infests 40,800 acres in Colorado

They are native to most of Europe and northern Asia. They were introduced into the U.S. in the 1800s. Yellow toadflax now occurs throughout the continental United States and in every Canadian province and territory.



Yellow toadflax leaves are narrow, linear and 1 to 2 inches long. The stems are woody at the base and smooth toward the top. The snapdragon-like flowers are bright yellow with a deep orange center and have a spur as long as the entire flower. It develops an extensive root system, making control difficult.

Toadflax is a perennial that reproduces from seeds and from underground root stalks. Spring emergence occurs around mid-April and depends primarily on temperature. A smaller fall flush of seedlings can occur in the fall.

The strong, upright floral stems that are characteristic of mature toadflax plants develop after a winter’s dormancy, and emerge about the same time as seedlings in mid-April. They produce thousands of seeds per plant which can be spread long distances by birds, animals and the wind. A single plant may produce over 500,000 seeds which are dispersed by wind, rain, wildlife, and movement of forage and livestock. The seed is disk-shaped with a 0.08-inch diameter, dark brown to black, often with irregular papery wings.

Seed dispersal begins a few weeks after flowering and continues into winter. A single plant can produce up to 30,000 seeds which can live in the soil for up to 10 years but, most grow by the next year.

They have an extensive root system which allows them to take water and nutrients from native plants. This extensive root system allows them to live indefinitely. The roots of a single plant can extend 10 feet and give rise to daughter plants every few inches.

Yellow toadflax displaces desirable plant communities reducing ecological diversity and rangeland value, and decreases forage for domestic livestock, some big game species and affects habitat for associated animal communities. The plant is known to be mildly poisonous to cattle. Goats and sheep have been known to graze the plants with little effect.

The seeds can be used by birds or rodents, but are not usually used by native species. Where toadflax infests, soil erosion, surface runoff and sediment increases.

Yellow toadflax can kill the existing plant life in an area where people want to grow crops. It also contains a poisonous glucoside that may be toxic to some animals.

Because the flower is largely closed by its underlip, pollination requires strong insects such as bees and bumblebees. The plant also provides food for a large number of insects, so there is some good with the bad. They are often grown in children’s gardens for the “snapping” flowers which can be made to “talk” by squeezing them at the base of the corolla.

Despite its reputation as a weed, like the dandelion, this plant has also been used in folk medicine for a variety of ailments. A tea made from the leaves was taken as a laxative, a strong diuretic, as well as for jaundice, dropsy and enteritis with drowsiness. For skin diseases and piles, either a leaf tea or an ointment made from the flowers was used. In addition, a tea made in milk instead of water has been used as an insecticide. It is confirmed to have diuretic and fever-reducing properties.

The key to controlling yellow toadflax is to limit vegetative spread of established colonies by cutting, pulling or spraying seed stalks prior to seed set, or by using insects to destroy flowers, seeds or damage plants. Once current seed production has been controlled, toadflax seedlings that emerge from the soil seed bank must be destroyed every year until the seed bank is diminished.

Don’t feel bad about cutting these flowers and using them in an arrangement. They need to be controlled!

Dr. Joanne Stolen is retired from teaching microbiology at Rutgers University.


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