PNW378 DWARF SNAPDRAGON

(Chaenorrhinum minus (L.) Lange)

Dwarf snapdragon is an annual that Flowers, borne in leaf axils along the Two round pores release seeds from flowers and produces seed while only stem, are about 1f4 inch long. the capsule. a few inches tall.

Dwarf snapdragon, a southern north end of Yellow head Lake in European native, is closely British Columbia. IDEN'I'IFICATION related to Dalmatian and yellow Dwarf snapdragon is a class A Dwarf snapdragon, a short, toadflax in the figwort family noxious weed in Washington. It upright annual with ascending (). Introduced as is not listed as a noxious weed in branches, usually grows less than seed in ships' ballast, dwarf Idaho or Oregon. 8 inches tall, but sometimes snapdragon was first observed in grows to 16 inches tall. Glandular the United States in Camden, hairs cover the entire . New Jersey, in 1874, and in Lower leaves are opposite and Canada in St. John, New oblong; others are alternate and Brunswick, in 1881. Since then, it linear, 3js to 1114 inches long. has spread westward across Flowers develop individually in North America to at least 30 the axils of small stem leaves. states and 9 provinces. In the Flowers resemble toadflax or Pacific Northwest, dwarf snapdragon flowers, but have a snapdragon has been reported in short spur. A two-lobed upper lip Boundary, Nez Perce, and Idaho touched with pale lavender counties, Idaho; in Spokane and arches above a three-lobed white Whitman counties, Washington; lower lip tinged with pale yellow in Union County, Oregon; and at Bluish purple spurred flowers , upper at the throat. The outside of the Burnaby, Agassiz, Elko, Fernie, right, produce two-celled capsule, flower, including the spur, is Wasa and Lucerne Station at the lower left. bluish purple.

A Pacific Northwest Extension Publication • Washington • Idaho • Oregon A literal translation from Greek extended period fall in the Dwarf snapdragon has a small of the name Chaenorrhinum, immediate vicinity of the parent taproot that is easy to pull. "gaping snout," refers to the . At maturity, the plant Destroy plants that have started open flower. The flower is about becomes brittle. Stems with seed to flower. Normally, mowing is 1/4 inch long and remains in capsules or whole plants break not practical because dwarf bloom for only 24 hours. The fruit off and are carried away by snapdragon flowers within is an egg-shaped capsule, passing trains or vehicles. inches of the ground. Where typically containing 40-60 small appropriate, establish Dwarf snapdragon is fully dark brown seeds. Seeds are competitive vegetation. released through two round self-compatible; most flowers are For chemical control pores at the top of the capsule. probably self-fertilized. Thus, a When wet, the capsules close, single seed can start a new colony recommendations, refer to the Pacific Northwest Weed Control preventing seed escape. following long distance dispersal. Dwarf snapdragon has spread at Handbook, an annually revised A native plant, blue-eyed Mary the rate of 10 miles per growing extension publication available ( parviflora), resembles season in eastern North America. from the extension offices of dwarf snapdragon. Differences Most spread has occurred along Oregon State University, include opposite leaves railroad tracks or on highway Washington State University and throughout and the absence of a rights-of-way in the "sterile strip" the University of Idaho. spur on the blue and white kept bare of vegetation. Most The author acknowledges the flowers of blue-eyed Mary. dwarf snapdragon in the Pacific support of the Washington State Kenilworth ivy (Cymbalaria Northwest grows along railroads Department of Agriculture and muralis), an introduced plant, has and roadsides, but plants also flowers similar to dwarf the Washington State Noxious grew in a winter wheat field, Weed Control Board in snapdragon, but has ivy-shaped among a planting of carrots in a preparation of this bulletin. leaves on trailing stems. garden, and on a ski hill. Normally, dwarf snapdragon grows in gravelly or sandy fill BIOLOGY AND material that would otherwise be bare or would support a sparse ECOLOGY cover of other plants. It is Dwarf snapdragon is a summer normally absent from areas of annual, reproducing by seed. dense vegetation. In Washington, Plants are susceptible to frost; the kochia (Kochia scoparia) and By Cindy Roche, M.S., Washington overwintering stage is seed. Two horseweed (Conyza canadensis) State University Extension factors contribute to the success sometimes grow with dwarf Coordinator, and Plant Scientist in of dwarf snapdragon: its ability snapdragon because they also Natural Resource Sciences. Photos by to produce seed in a short time rapidly colonize newly disturbed author. and a dispersal mechanism that sites. Issued by Washington State carries it to open sites. In eastern University Cooperative Extension, North America, scientists Larr G. James, Interim Director; collected flowering and fruiting CONTROL Oregon State University Extension plants in most regions within a Early detection and quick Service, 0. E. Smith, Director; month of the final spring frost. In response are crucial for dwarf University of Idaho Cooperative a study in New York, plants snapdragon control because the Extension System, LeRoy D. Luft, began to flower 45 days after time from germination to mature Director; and the U.S. Department of germination. In regions of seed is short. Prevent seed Agriculture in furtherance of the Acts summer drought, two flowering production consistently to control ofMay8andJune30,1914. peaks occur, a major one before the population. Studies in New Cooperative Extension programs and the onset of summer moisture York indicate that the proportion policies comply with federal and state stress and a minor one in late of seeds remaining viable over laws and regulations on summer or fall. Scientists in New winter and germinating the next nondiscrimination regarding race, York found that the time from year may be quite small (5 to color, national origin, religion, drop to seed ripening is 10%). Seeds buried in soil of a gender, age, disability, and gender about 14 days in mid-season field showed 90% reduction in preference. Trade names have been used to simplify information; no (July) and about 21 days in late viability over a 2-year period. endorsement is intended. Published season (September). Seeds shaken However, a single seed can November 1991.50/0/50 from the capsules over an reestablish the population. PNW378 2