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Biology and Management of the Toadflaxes Page 2 was widely distributed in North America by the mid 20th century. Unfortunately in states where yellow Figure 1. YELLOW TOADFLAX, butter- and-e ggs, wild snapdragon (Linaria toadflax is not noxious, it still is sold by some vulgaris Miil.). Noxious. Figwort family. nurseries as °butter and eggs" Or as °Wlld This introduced creeping perennial is an snapdragons." escaped ornamental that reproduces by seed and extensive hor¢ontal roots. BIOLOGY stems are smooth, erect, teary, often in Humps, and 1 to 2 1/2 feet tall. Numerous pale green leaves are Germination and Emer enCe 9 alternate, narrow, pointed at both ends, and 2 1/2 or more inches long. Flowers resemble those of cultivated Seeds of ellow toadflax erminate and emer a In Y g g snapdragon; each has a spur extending below from the lower lip of the corolla. early to mid-May while Dalmatian toadflax seeds may They are about 1 inch long, bright germinate and emerge earlier especially on south or Yellow with a bearded, orange throat southeast facing slopes. Ln Washington, Dalmatian and occur in kerminal, somewhat toadflax seedlin S On SOUth faCln SIO eS USU811 g g P Y elongated clusters with the youngest Flowers at the tip. The fruit is a brown, emerge in early to mid-March. First year Dalmatian globe-shaped, two-celled capsule, 1/4 toadflax plants often produce prostrate shoots in fall inch in diameter containing many that survive into the following spring. Mature seeds. Seeds are small, round, rough, Dalmatian toadflax'ma roduce rostrate shoots but Y P P r flattened, with a papery, notched circular wing, dark brown, and about to a lesser extent, and these typically die before 1/12 inch in diameter. It is a winter and shoots emerge the following spring from Persistent, aggressive invader in roots. Yellow and Dalmatian toadflax shoots that row g C°Iorado from 6,000 to 8,500 feet mostly on the Wes[em Slope. from roots emerge as early as mid-March along the Front Range in Colorado, but vegetative shoot emergen ce may not begin until mid- to late June at 4,000 feet to 10,000 feet. In Canada, vegetative shoots begin to emerge when soil temperatures range from 42 to 50 F. Root growth 4 Seedling root develop is slow and represents a life stage vulnerable to control attempts and plant competition. Disturbance promotes toadflax invasion and may be necessary for establishment to occur. However once established, toadflaxes readily spread into adjacent non-disturbed areas. Much of this spread is by vegetative means, reflecting a vigorously-growing root system. Dalmatian toadflax roots may grow 20 inches deep or more nine weeks after seedlings have emergedand have vegetative buds that give rise to new shoots. Patch expansion can be drematic. In Colorado, Dalmatian toadflax shoot density increased over 1,200 percent in six years at one location and 190 percent over three years at another. Yellow toadflax seedlings produce vegetative shoots from root buds two to three weeks after germination. Mature toadflax have well-developed and extensive root systems. Dalmatian toadFlaz roots may penetrate the soil 4 feet to 10 feet and lateral roots may extend 10 feet from the parent plant; while yellow toadflax roots grow 3 feet deep or more with lateral roots that may extend several yards. Flowering Dalmatian toadflax typically Flowers begining in late May or June in Colorado and may continue until fall, particularly if moisture is not limiting. Yellow toadflax begins to Flower when shoots are from 16 to 24 inches tall, mid- to late May along the Front Range in Colorado, although at higher elevations (9,000 feet or more), flowering may not begin until Tate July. Yellow toadflax may not flower until fall under drought conditions. Yellow toadflax shoot phenology in any given patch may range from vegetative to flowering to seed set, depending on the time of season and environmental conditions (particularly moisture). This contributes to management difficulties. MANAGEMENT All toadflax species are very difficult to control and http://www.ext.colostate.edu/pubs/natres/03114.htm1 6/20/2005