Yellow Toadflax
Linaria vulgaris
Class A Noxious Weed
This plant is new to the state and has been designated a Class A Noxious Weed by the New Mexico Department of Agriculture.
Agricultural Threat
This plant threatens our state's food security and economy by reducing agriculture yields and/or degrading soil resources.
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Livestock Hazard
This plant presents a threat to the health and/or quality of livestock.
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Commercially Available
Despite being classified as a noxious weed, this plant is still widely sold in stores! Keep an eye out, and remember that it is illegal to plant and transport noxious weeds in the state of New Mexico.
QUICK FACTS
- Yellow toadflax is an invasive perennial that aggressively spreads through its extensive creeping root system, often leading to significant ecological and agricultural impacts. It outcompetes desirable plants by sequestering water.
- It was introduced to North America in the 1600s as a decorative garden plant. Today, it is naturalized in almost every U.S. state and Canadian province, where it is considered a noxious weed in many regions.
- The plant significantly increases erosion risk, harms the agricultural economy, and displaces native plants and wildlife.
1. Overview
The wolf in wildflower’s clothing.
Whimsically nicknamed “butter-and-eggs,” yellow toadflax is a short-lived perennial plant known for its bright yellow and orange flowers resembling a sunny-side-up egg. Native to Eurasia and introduced to North America, it has become widespread along roadsides, fields, and disturbed areas. While its vivid appearance may add a cheerful aesthetic to flower gardens, yellow toadflax is a highly invasive species in many regions of the world, where its aggressive vegetative reproduction and spread can outcompete native vegetation and disrupt agricultural efforts.
History of Yellow toadflax
Yellow toadflax (also known as butter and eggs) was initially brought to North America as a high-society addition to gardens. It was also used for fabric dyes and traditional folk medicine. Traditionally used by the Mennonites to dye their own fabrics and clothing, they widely propagated the plant in the colonial United States, contributing to its escape. In the West, it propagated from the residents of mining towns who used it as an affordable, hardy addition to flower gardens. It is now naturalized in almost every U.S. state and Canadian province. It is considered a noxious weed in many states and is restricted in Alaska. [1,2,8]
Unlike most noxious weeds, the introduction of yellow toadflax to the United States was attributed to one man named Mr. Ranstead. Ranstead, originally from Wales, accompanied William Penn to Delaware in the late 1600s and was an upholsterer by trade. He ordered yellow toadflax from his native country as an addition to his flower garden and to share it with his neighbors as the plant was believed to repel insects. The unfortunate Mr. Ranstead was likely unaware of the weed’s ramifications and was subsequently blamed by notable authors and botanists of the 19th century for its invasion. Subsequently, the alternate name “Ranstead weed” has been carried down through the plant’s history. [3,4,5,8]
2. ID Guide
What does it look like?
Toadflaxes are perennial, creeping, woody plants with very similar attributes. In the United States, three toadflax species are listed as noxious: Dalmatian toadflax is divided into broadleaf (L. dalmatica) and narrowleaf (L. genistifolia) varieties. Yellow toadflax (Linaria vulgaris) is similar to the Dalmatian toadflaxes but can be distinguished by smaller, whiter flowers and globe-shaped fruit. Yellow toadflax is shorter (1.5-3 feet), while Dalmatian toadflax is usually taller (3+ feet). Dalmatian toadflax tends to have thick, heart-shaped, waxy leaves, while yellow toadflax leaves are linear and soft. Dalmatian toadflax can occasionally hybridize with yellow toadflax. Dalmatian toadflax mainly propagates via seed germination with success rates of about 75%, while yellow toadflax primarily spreads by creeping roots, with only about a 10% seed germination rate. [1,4,6]
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Key Features
- Plant: Grass-green, branching stems growing 1-3 feet tall are woody at the base, soften closer to the top, and are often hairy. The above-ground portion of the plant mostly dies back in winter (with the exception of prostrate stems) while the roots remain alive underground. [1,4]
- Roots: Yellow toadflax produces particularly hardy, extensive creeping roots that allow for primary reproduction through rhizomes. The vertical roots penetrate the soil about 3 feet. The lateral roots branch off from the vertical roots and can extend in a 10-foot or more radius, remaining close to the soil surface. Buds that develop on the lateral roots quickly produce new shoots. Roots may form mutualistic relationships with vesicular-arbuscular mycorrhizae. [1,4]
- Leaves: Narrow linear 3/4-4 inch leaves are like-colored to the stem and are usually alternate but may appear whirled or opposite on the stem. Leaves are symmetrical, blade-like, and smooth-edged, pointed at both the apex and base. They have smooth margins and begin to droop about halfway down the length. [1,4]
- Flowers: Flowers appear May-September and are snapdragon-like, with buttery white conjoined petals and a yellow-orange (egg) in the center. A long spur protrudes from the bottom of the flower, and stamens are in pairs of two (four stamens per flower). The tubular flowers crowd the top of the stem in branch clusters (racemes). [1,4]
- Seeds: Fruit pods contain light, papery seeds that allow for slight wind dispersal. Blackish seeds are flat, with a papery wing encircling them. Mature plants can produce up to 1,500-3,000 seeds, which remain viable in the soil for up to 10 years. Pods are 2-chambered, each containing 10-40 seeds. [1,4]
Dave Powell, USDA Forest Service (retired), Bugwood.org
Flowers appear May-September and are snapdragon-like, with buttery white conjoined petals and a yellow-orange (egg) in the center.
Sandy Wolkenberg, inaturalist.org
This perennial primarily reproduces through its prolific creeping root buds. Most shoots emerge between early April and June, with later emergence in colder climates.
Steve Dewey, Utah State University, Bugwood.org
Yellow toadflax produces particularly hardy, extensive creeping roots that allow for primary reproduction through rhizomes.
John Cardina, The Ohio State University, Bugwood.org
Narrow linear 3/4-4 inch leaves are like-colored to the stem and are usually alternate but may appear whorled or opposite on the stem.
L.L. Berry, Bugwood.org
Grass-green, branching stems growing 1-3 feet tall are woody at the base, soften closer to the top, and are often hairy.
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
Fruit pods contain light seeds that allow for slight wind dispersal. Blackish seeds are flat, with a papery wing encircling them.
3. Infestation Basics
“This is extensively naturalized and has become a vile nuisance in our pastures and upland meadows… Although the flowers are somewhat showy, it is a fetid, worthless and very objectionable weed, -the roots very tenacious of life- and requiring much preserving effort to extirpate them.”
-William Darlington, 1859
Where does it grow, and how does it spread?
Yellow toadflax spreads primarily through its creeping root system. The plant is weak in its early seedling stage, and taking action during the first weeks of its life is key to its eradication.
Yellow toadflax thrives across various environments, including roadsides, pastures, residential areas, cemeteries, gravel pits, well-drained riparian zones, and waste areas. While it prefers disturbed sites, it can also take hold in undisturbed habitats. This plant frequently colonizes naturally open spaces within sagebrush ecosystems, ponderosa pine forests, and other woodland or parkland areas. Tolerant of subarctic conditions, yellow toadflax is most common in sunny locations with well-drained, coarse-textured soils. It typically grows at elevations between 6,000 and 9,500 feet and is found in every state except Hawaii. [1,6,7]
This perennial primarily reproduces through its prolific creeping root buds. Most shoots emerge between early April and June, with later emergence in colder climates. Once seedlings lose their cotyledons (first leaves), they closely resemble vegetative shoots. However, unlike regenerative shoots, seedlings have low survival rates, particularly under drought conditions or competition from other plants. Although cheatgrass can effectively outcompete yellow toadflax, it is not a viable management solution, as cheatgrass is also a noxious species. Young yellow toadflax plants typically struggle to survive in areas with low precipitation or dense ground cover, an important factor to consider when planning control strategies. Once its root system is fully established, the plant becomes less dependent on water and significantly more challenging to manage. [1,4]
In its first year, yellow toadflax plants will produce 90-100 new vegetative shoots and 200-250 in its second year. Floral stems will produce flowers from May to September, but only if the plant has experienced a period of dormancy. Seeds will only appear if cross-pollination is possible. [4]
After about four weeks, the roots become more developed, and the plant can forcefully compete with its neighboring species. Vertical roots can reach depths of about 3 feet. Lateral roots can grow to reach a ten-foot radius around each plant. Most regenerative buds will be found on lateral roots 2-8 inches deep. [1,4]
Seeds develop first near the lower part of the stem while the upper portion remains in full bloom, resulting in seeds and flowers coexisting on the plant. Seed dispersal starts in August-September and continues through the winter. With a germination rate of only about 10%, seeds generally do not travel far unless transported by water or over crusted snow. Around 80-90% of the seeds fall within 18 inches of their source. Plants can not self-pollinate but are highly pollinated by insects. [1, 4]
Plants typically live about 4 years, but quickly establish subsequent generations so that a yellow toadflax stand could exist perpetually. [1]
Key takeaway: The most effective preventative measure is to identify and remove the plant within the first few weeks of its life. Established ground cover provides strong competition, significantly deterring yellow toadflax invasion.
Why is it so invasive?
Once established, yellow toadflax outcompetes native plants and crops by aggressively monopolizing available water. In large quantities, it can also pose a health risk to cattle.
Yellow toadflax contains quinazoline alkaloids, which may be toxic to livestock if consumed in significant quantities. However, few cases of livestock poisoning have been reported. Goats and sheep have been observed eating this plant with little to no adverse effects. [1,8]
The presence of yellow toadflax negatively impacts wildlife, including big game, by reducing the availability of diverse forage. Its displacement of native plants primarily diminishes the economic value of wildlife habitats and rangelands. While a major concern for wild areas, this weed poses its greatest threat to agricultural lands. [1]
Key takeaway: Yellow toadflax displaces native plants, reduces forage diversity for wildlife, and diminishes the economic value of rangelands and agricultural fields.
Common risk factors for invasion
- Overgrazing: When livestock are allowed to graze in a single area for too long, they will rip through the existing vegetation and expose the top layer of soil. This creates an opening for yellow toadflax, but this risk can be mitigated by practices that move cattle around more frequently.
- Areas of neglect: Yellow toadflax needs time to establish and thus can target abandoned areas where it will not likely be disturbed. Events of no-till farming can enable the plant to take hold, as frequent disturbance will often damage the root structure. Practices such as overgrazing, lack of crop rotation, and inadequate weed control increase vulnerability to invasion.
- Open spaces: Open sites with long days of full sunlight and little canopy, such as pastures, fields, open grazing allotments, south-facing slopes, etc., are at risk for particularly aggressive infestations.
Impacts
Economic
This weed will become a monoculture through aggressive seed production and vegetative growth. Aside from big game, it can reduce available forage for domestic livestock and, in rare cases, cause harm to cattle. Yellow toadflax primarily affects rangelands and agricultural lands, while Dalmatian toadflax tends to be a more significant threat to wild habitats. In Alberta, Canada, a 1987 study of 69,188 infested acres resulted in an estimated loss of $360,000 per year due to the plant’s presence. In addition to its other agricultural risks, the plant can carry and spread pathogens such as cucumber mosaic and broad bean wilt viruses. [1,4]
Ecosystem Health
Once established, yellow toadflax displaces native plants, resulting in a notable loss of floral and faunal biodiversity. This can significantly reduce forage availability for game, particularly during the winter months, and may even alter migratory patterns. While deer, sheep, certain birds, and rodents occasionally consume yellow toadflax, it is generally not considered a reliable forage source, as most animals tend to avoid it. Some wildlife may use the plant for shelter, but this typically occurs in areas where the toadflax itself has already replaced preferable shelter. [1,7]
Erosion
Yellow toadflax significantly increases the risk of soil erosion by outcompeting and displacing native bunchgrasses and ground cover. These native plants play a crucial role in stabilizing soil with their extensive root systems, which help bind the soil and reduce runoff. When yellow toadflax takes over, it replaces these stabilizing plants with its shallow, less effective root structure, leaving the soil more vulnerable to wind and water erosion. In areas where there is already little vegetation or in areas of primary succession such as mines, it is possible that toadflax species may help stabilize the soil until more favorable plant communities take over. [1]
4. Management Strategies
Yellow toadflax struggles to establish itself in areas with strong, well-established grass and forb communities. Encouraging the growth of native plants and maintaining healthy cover crops is the most effective first step in preventing the weed from taking root. Once yellow toadflax becomes a fully established monoculture, a combination of management strategies may be required to eradicate the plant thoroughly. [1]
An effective management strategy involves the successful re-vegetation of desirable plants, which can out-compete and crowd out potential invasions. Although grazing often increases the risk of infestation, targeted grazing by sheep and goats can be helpful in controlling small patches or areas that are difficult to access. However, mowing, grazing, and burning methods are generally ineffective, as they fail to address the weed’s extensive and resilient root system. Manual removal by tilling can be successful in small areas if repeated for 7-10 days during the growing season. [1,6]
DO’s
- Identify the plant when young; young shoots are weak and die quickly without ideal conditions.
- Encourage healthy cover crops and vegetation to promote native plant growth. These can outcompete yellow toadflax and help prevent its establishment.
- Consider manual removal by tilling in small areas, repeating the process regularly throughout the growing season to reduce the plant’s spread.
DON’Ts
- Overgraze or frequently till fields and pastures, as this can allow the weed to gain a foothold.
- Mow, burn, or graze as these methods leave behind root fragments, further spreading the infestation.
- Ignore early infestations—taking action in the first few weeks of yellow toadflax’s life is crucial for successful early eradication.
** The following information is provided courtesy of the UC Weed Research and Information Center. The Taos Soil and Water Conservation District does not endorse the use of any particular product, brand, or application thereof. **
Yellow Toadflax can be managed through repeated hand-pulling, mowing before flowering, and promoting competitive vegetation like native grasses to suppress its growth. Long-term control may be enhanced by introducing biological agents such as specialist insects.
Hand-pulling |
Hand pulling is only effective on seedlings before plants become established and the extensive creeping root system develops. |
Mowing |
Mowing can prevent the plant from going to seed, but mowing also stimulates vegetative reproduction from the lateral roots and rhizomes. |
Tilling |
Tilling on arable lands can be effective but tilling needs to be done every 7 to 10 days over the course of the season and repeated yearly for several years to eradicate resprouting root fragments. |
Grazing is not considered an effective control option. Overgrazing can reduce competition and increase site disturbance, creating an ideal environment for toadflax establishment. The plant is not preferred by grazing livestock and contains quinazoline alkaloids that are moderately toxic.
Fire is not effective because the underground root system is not damaged and will resprout.
Reseeding with competitive annual and perennial grasses reduces survival and helps prevent further spread.
Two insects active on yellow toadflax were accidentally introduced into the United States in the early 1900s. The toadflax flower feeding beetle (Brachypterolus pulicarius) and the toadflax capsule weevil (Gymnetron antirrhini) are well established in the Pacific Northwest. Both significantly reduce seed production, but do not have a significant impact on populations. However, the most promising biocontrol agent is the toadflax stem-mining weevil (Mecinus janthinus). It is too early to know how successful this insect will be.
The following specific use information is based on published papers and reports by researchers and land managers. Other trade names may be available, and other compounds also are labeled for this weed. Directions for use may vary between brands; see label before use. Herbicides are listed by mode of action and then alphabetically. The order of herbicide listing is not reflective of the order of efficacy or preference.
|
2,4-D Several names |
Rate: 2 to 4 pt product/acre (0.95 to 1.9 lb a.e./acre) Timing: Postemergence when plants are growing rapidly. Applications in spring provide best control. Remarks: 2,4-D is a selective herbicide for broadleaf species. In areas where desirable grasses are growing around toadflax, 2,4-D can be used without non-target damage. Good coverage is necessary. Efficacy is improved when tank-mixed with picloram, chlorsulfuron, or metsulfuron |
|
Aminocyclopyrachlor + chlorsulfuron Perspective |
Rate: 4 to 6 oz product/acre plus 0.25 to 0.5% v/v surfactant Timing: Postemergence when plants are growing rapidly in the bud to bloom stage. Remarks: Perspective provides broad-spectrum control of many broadleaf species. Although generally safe to grasses, it may suppress or injure certain annual and perennial grass species. Do not treat in the root zone of desirable trees and shrubs. Do not apply more than 11 oz product/acre per year. At this high rate, cool-season grasses will be damaged, including bluebunch wheatgrass. Not yet labeled for grazing lands. Add an adjuvant to the spray solution. This product is not approved for use in California and some counties of Colorado (San Luis Valley). |
|
Picloram Tordon 22K |
Rate: 2 qt product/acre (1 lb a.e./acre) plus 0.25 to 0.5% v/v surfactant Timing: Postemergence when plants are growing rapidly in spring before full bloom, or in late summer to early fall. Remarks: High levels of picloram can give long-term soil activity for broadleaves. Picloram at 2 pt product/acre plus 6 oz Overdrive/acre controlled yellow toadflax better (98% control) than picloram at 2 qt product/acre (70% control) 2 years after treatment. Tordon 22K is a federally restricted use pesticide. It is not registered for use in California |
|
Picloram + 2,4-D Tordon 101M
|
Rate: 2 qt product/acre plus 0.25 to 0.5% v/v surfactant Timing: Postemergence when plants are growing rapidly in spring before full bloom. Remarks: May require annual treatment for 2 to 3 years. High levels of picloram can give long-term soil activity for broadleaves. Tordon 101M is a federally restricted use pesticide. It is not registered for use in California. |
|
Picloram + chlorsulfuron Tordon 22K + Telar |
Rate: 1 qt product/acre Tordon 22K + 1.25 oz product/acre Telar plus 0.25 to 0.5% v/v surfactant Timing: Postemergence when plants are growing rapidly from bloom through fall. Fall treatments give best control. Remarks: High levels of picloram can give long-term soil activity for broadleaves. Retreatment may be necessary. Tordon 22K is a federally restricted use pesticide. It is not registered for use in California. |
|
Glyphosate Roundup, Accord XRT II, and others |
Rate: Broadcast treatment: 1 to 2 qt product (Roundup ProMax)/acre (1.1 to 2.25 lb a.e./acre). Spot treatment: 1.5 to 2% solution v/v Roundup (or other trade name) and water to thoroughly wet all leaves Timing: Postemergence when plants are growing rapidly. Applications in early spring provide best control. Remarks: Glyphosate is a nonselective systemic herbicide with no soil activity. Repeated applications may be necessary for complete control. |
|
Chlorsulfuron Telar |
Rate: 2 to 2.6 oz product/acre (1.5 to 1.95 oz a.i./acre) plus 0.25 to 0.5% v/v surfactant Timing: Postemergence when plants are growing rapidly in the bud to bloom stage. Remarks: Chlorsulfuron is a selective herbicide effective for controlling broadleaves and grasses. While it is often stated that Telar provides only suppression of yellow toadflax and is often tank mixed with picloram or 2,4-D, this depends on the timing of the application. Telar will control yellow toadflax, but timing is of critical importance. In a research report, 1.75 oz product/acre Telar gave 76 to 98% control 2 years after treatment. This treatment was applied when most of the shoots had already flowered so that adventitious root bud activity had begun. |
|
Imazapic Plateau |
Rate: 12 oz product/acre (3 oz a.e./acre) plus 1 qt/acre methylated seed oil in the spray mix Timing: Postemergence in fall when top 25% of the plant is necrotic, usually after a hard frost. Remarks: Imazapic is a selective postemergence herbicide effective for controlling broadleaf weeds and some grasses. It is not registered for use in California. |
|
Imazapyr Arsenal, Habitat, Stalker, Chopper, Polaris |
Rate: 3 pt product/acre (12 oz a.e./acre) plus 0.25 to 0.5% v/v surfactant Timing: Postemergence when plants are growing rapidly. Remarks: Imazapyr is a preemergent and postemergence herbicide effective for controlling broadleaf weeds and grasses. It has fairly long soil residual activity and at the high rates needed, it will often leave bare ground. Best used in spot treatments. |
|
Metsulfuron Escort
|
Rate: 1.5 to 2 oz product/acre (0.9 to 1.2 oz a.i./acre) plus 0.25 to 0.5% v/v surfactant; efficacy is improved with the addition of 2,4-D at a rate of 1 qt product/acre Timing: Early postemergence. Remarks: Metsulfuron is a selective herbicide for broadleaf species. It provides only suppression of yellow toadflax. In areas where desirable grasses are growing around toadflax, metsulfuron can be used without non-target damage. It is not registered for use in California. |
5. Citations
[1] Sheley, Roger L., and Janet K. Petroff. Biology and Management of Noxious Rangeland Weeds. Oregon State University Press, 1999.
[2] USDA. “USDA Plants Database.” Usda.gov, 2025, plants.usda.gov/plant-profile/LIVU2. Accessed 3 Jan. 2025.
[3] Darlington, William. American Weeds and Useful Plants. A.O. Moore, 1859.
[4] USFS. Field Guide to Noxious and Invasive Weeds Known to Occur or Are Potentially Occurring on the Apache-Sitgreaves National Forests. 2008.
[5] Watson, John Fanning. Annals of Philadelphia. New York, NY, E.L. Carey & A. Hart, 1830.
[6] USFS. Field Guide for Managing Dalmatian and Yellow Toadflaxes in the Southwest. 2014
[7] Anderson, Lars W., et al. Weed Control in Natural Areas in the Western United States. Davis, California, University Of California Weed Research And Information Center, 2013.
[8] Government of Saskatchewan. “Toadflax | Problem Weeds – a Cattlemen’s Guide | Government of Saskatchewan.” www.saskatchewan.ca, www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/livestock/pastures-grazing-hay-silage/problem-weeds—a-cattlemens-guide/toadflax. Accessed 3 Jan. 2025.
[9] Pratt, Anne. Wild Flowers. 1799. London, UK, The Committee of General Literature and Education, 1852.
[10] Gustafsson, Å. Linnaeus’ Peloria: The history of a monster. Theoret. Appl. Genetics 54, 241–248 (1979). https://doi.org/10.1007/BF00281206
L.L. Berry, Bugwood.org
Fun Facts
In the ancient world, toadflax was widely known and used to treat various ailments and afflictions. A dated medicinal belief called the “doctrine of signatures” promoted the idea that plants would cure the part of the body they resembled. Toadflax became a prime example of this with its “throat-like” appearance. Subsequently, people of the Middle Ages used toadflax to treat throat ailments, primarily scrofula, an enlargement of the lymph glands. [8]
Caleb Slemmons, National Ecological Observatory Network, Bugwood.org
“This showy flower is a very frequent one on the rural landscape… On corn lands, as well as on pastures where the soil is sandy, it is often very troublesome to the cultivator…”
-Anne Pratt, 1852
John Cardina, The Ohio State University, Bugwood.org
Fun Facts
Other medicinal uses included relieving ulcers, removing obstructions in the liver and spleen, curing eye discomfort, and relieving various skin ailments such as sores, pimples, “piles,” “scurf wheals,” “ugly sores,” and even leprosy. [8]
Priyantha Wijesinghe, inaturalist.org
Theo Ozga, inaturalist.org
Fun Facts
In terms of lore and ancient belief, it was believed that three toadflax seeds in conjunction with linen thread would prove to be a sufficient ward against all kinds of evil. One could also rid themselves of curses and evil spells by walking around a blooming toadflax plant three times. Other supposed functional uses of toadflax included insect-repelling lotion and, when used in combination with boiled milk, an early insecticide [8,9]
kokokopriva, inaturalist.org
Fun Facts
Toadflaxes, as well as snapdragons and foxgloves, are capable of peloria. This mutation causes a flower to switch from bilateral to radial symmetry, becoming “monstrous” and creating an entirely new flower. In 1744, Carl Linnaeus was fascinated by this concept and could selectively breed thousands of flowers, repeatedly isolating mutations until some plants produced only peloric flowers. [10]
raingerr, inaturalist.org
sorrento1837, inaturalist.org