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Federal Noxious Weed TDA Noxious Weed TPWD Prohibited Exotic Species 
Invasive Plant Atlas of the USNOTE:
means species is on that list.
Linaria vulgaris
Yellow toadflax
Synonym(s): Linaria linaria (L.) Karst., nom. inval.
Family: Plantaginaceae (formerly Scrophulariaceae)
Duration and Habit: Perennial Herb
Photographer: Arnstein Rønning
Source: Wikimedia Commons
Description
Unless otherwise noted, the following is from Zouhar (2003).
Yellow toadflax is an erect, herbaceous, short-lived perennial from less than 1 ft to nearly 3 ft tall. It has long, thin leaves, 1 to 2 in (2.5 to 5 cm) long, that are pointed with a narrow, tapering base; pale green with a silvery tinge. They are arranged alternately, but may grow so closely along the stem that they appear to be whorled or opposite (Chayka 2014). The leaf margins are entire, and the leaves are not hairy (Chayka 2014). Older leaves have a single vein visible on the underside.
Stems: Yellow toadflax stems range from less than 1 ft (31 cm) to nearly 3 ft (0.9 m) tall, and are generally unbranched, or at most, sparsely branched. A single yellow toadflax plant can produce several woody stems. The woody stems usually have a reddish color at the base, becoming more slender, succulent, and greener toward the growing tip. Stems are hairless (Chayka 2014).
Flowers: Yellow toadflax flowers are pale yellow, two-lipped, spurred, snapdragon-like blossoms that are 0.8 to 1.6 in (2 to 4 cm) long. The upper lip is double-lobed and the lower lip has three lobes (Chayka 2014). The long spur contains nectar (Chayka 2014). Unlike Dalmatian toadflax flowers, the bearded throat of yellow toadflax flowers is bright orange (hence the common name “butter-and-eggsâ€). Flowers are clustered at the top of the stem in groups of six to 30.
Seeds: Seeds are produced in an upright, oval, two-celled seed capsule. Each stem can produce up to 30 capsules, with each capsule yielding up to 250 seeds. The seeds are small, lightweight, winged discs, 0.06 in (0.02 mm) in diameter.
Native Lookalikes: Currently no information available here yet, or there are no native Texas species that could be confused with Yellow toadflax.
Ecological Threat: The following is from Zouhar (2003).
Its ability to produce large numbers of seeds and to spread horizontally by root sprouts means is can easily invade and persist. Once established, it can crowd out other plants, and its deep tap root and spreading horizontal roots means it competes well for water and nutrients. On the other hand, it is a source of nectar for pollinators, can provide cover for small animals, and the seeds may be eaten by some species of birds and rodents, but not heavily.
It will especially do well in disturbed sites, as well as in cultivated fields, pastures and rangeland. Severely damaged plants, such as those killed by wildfire, can quickly regenerate from the stout, soil-protected roots. This enables yellow toadflax to become a dominant member of post-fire plant communities. In cropland, severed root fragments can spread across a field during cultivation, giving rise to new toadflax patches.
The effects of toadflax on fire frequency and intensity may be varied.
Biology & Spread: The following is from Zouhar (2003).
Reproduces by producing copious amounts of seeds, as well as vegetatively via lateral roots.
A large, mature yellow toadflax plant can produce over 7,500 seeds per stem and between 15,000 and 20,000 seeds per plant.
Viability of yellow toadflax seeds is low, and spring germination rates of less than 10 percent are typical. Some viable seeds can remain dormant in the soil for several years. Seedlings are weak competitors, and mortality rates can be high during drought conditions.
Established seedlings produce a taproot within two to three weeks after germination, and soon after begin to produce creeping, horizontal roots. Yellow toadflax is deep- rooted; thus, it competes well for water and nutrients. Its taproot can penetrate 3.3 ft (1.2 m) into the soil, and lateral roots can extend greater than 3 ft (0.9 m) from the plant. These spreading roots can produce up to 100 shoots during the first summer, creating crowded patches of yellow toadflax. Yellow toadflax roots have a lifespan of about four years.
Young shoots grow rapidly, and flower from late June until late autumn. Yellow toadflax flowers are cross-pollinated by bumble bees and other large bees; in areas where bees are sparse, limited pollination may result in low seed production. Yellow toadflax seeds are released from the dry seed capsules beginning in August and continuing through winter. Seed capsules maturing late in the season (November) contain more viable seeds than those maturing earlier in the season (September).
Aboveground parts of yellow toadflax plants are winter-killed, but protected buds at the soil surface and buds on creeping roots produce actively growing shoots the following spring. While most new infestations are probably started by seeds, spread of established infestations is mostly vegetative from shoots sprouting from the large network of creeping roots.
History: Introduced to North America as early as the late 1600s for horticultural and medicinal purposes (Zouhar 2003). It can be bought at nurseries and online, although several states prohibit its sale.
U.S. Habitat: It will especially do well in disturbed sites, as well as in cultivated fields, pastures and rangeland.
Distribution
U.S. Nativity: Non-native
Native Origin: Eurasia (Southeastern Europe and southwestern Asia)
U.S. Present: All U.S. states except Hawai’i.
Distribution in Texas: For distribution by counties in U.S., see http://www.swcoloradowildflowers.com/Yellow%20Enlarged%20Photo%20Pages/linaria.htm. Scroll to bottom of page. [Accessed Dec. 5, 2014]
Mapping
Invaders of Texas Map: Linaria vulgaris
EDDMapS: Linaria vulgaris
USDA Plants Texas County Map: Linaria vulgaris
Native Alternatives
Flowers resemble those of Dalmatian Toadflax (L. dalmatica), However, Dalmatian Toadflax has broad leaves.
Management
The best way to manage toadflax is to prevent it from establishing. This means vigilant monitoring of disturbed areas, especially if they are near established toadflax populations. Keeping the native plant community healthy goes a long way to preventing toadflax from establishing as the seedlings are poor competitors.
Physical: Can pull by hand, or mow, but any remnant roots will re-sprout. Discing/plowing is not recommended as it can leave root remnants as well as drag them to new places in fields. Mowing/cutting as plants begin to flower can prevent seed production, and repeated mowing/cutting over several years can deplete the stores in the deep tap roots; this is likely infeasible, especially in a natural/native plant area. Tilling can kill seedlings, but again, this is likely to be infeasible in natural areas.
Fire will not kill either toadflax species, as they will sprout from the surviving deep roots. Seeds can survive in the seed bank, but no studies have been done on the effects of fire on seeds. Fire may even aid the dominance of toadflax by removing competition (Zouhar 2003).
Chemical: Minnesota DNR suggests using herbicide with 2,4D, but may require repeated application, especially if there is a good seed bank (Chayka 2014).
Zouhar (2003) provides extensive discussion of the use of herbicides (http://www.fs.fed.us/database/feis/plants/forb/linspp/all.html#IMPACTS%20AND%20CONTROL). Picloram appears to be the most effective, but it kills non-target plants and does not provide complete control. “Permanent, long-term control of toadflax cannot be achieved with herbicide treatment alone†(Zouhar 2003). Use of herbicides that kill other plants can lead to a reduction of competition and therefore an increase in toadflax.
Biological: See Wilson et al. (2005) for a complete guide to using biological control. They discuss 7 species of insect that can help to control Yellow and Dalmatian Toadflax: Toadflax flower-feeding beetle (Brachypterolus pulicarius), Toadflax defoliating moth (Calophasia lunula), Toadflax root-boring moth (Eteobalea intermediella), Yellow toadflax root-boring moth (E. serratella), Toadflax stem-mining weevil (Mecinus janthinus), Toadflax seed-feeding weevils (Rhinusa antirrhini* and R. neta*), and Toadflax root-galling weevil (Rhinusa linariae*) [* formerly Gymnetron].
Cattle avoid yellow toadflax due to its containing several secondary compounds such as glycosides (Zouhar 2003). Goats have been used to control Dalmatian toadflax, but yellow toadflax appears to be unpalatable.
Text References
Wilson, L. M., S. E. Sing, G. L. Piper, R. W. Hansen, R. De Clerck- Floate, D. K. MacKinnon, and C. Randall. 2005. Biology and Biological Control of Dalmatian and Yellow Toadflax. USDA Forest Service, FHTET-05-13. [http://www.invasive.org/weedcd/pdfs/ToadflaxBook.pdf Accessed 2014, November 5]
Online Resources
http://www.invasivespeciesinfo.gov/plants/yellowtoadflax.shtml
http://plants.usda.gov/core/profile?symbol=LIVU2
http://www.invasive.org/weedcd/pdfs/ToadflaxBook.pdf
Chayka, Katy. 2014. Minnesota Wildflowers, a field guide to the flora of Minnesota. http://www.minnesotawildflowers.info/flower/butter-and-eggs. [2014, November 8]
Zouhar, Kris. 2003. Linaria spp. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/plants/forb/linspp/all.html [2014, November 5].
Search Online
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Invasive Plant Atlas of the United States: Linaria vulgaris
Bugwood Network Images: Linaria vulgaris
