Scientific Name: Delphinium spp.
Distribution: Western United States and Western Canada
Type of Poison: Alkaloids
Signs of Poisoning:
Growth Characteristics: There are a number of species which can be categorized into the tall-growing larkspurs. They are tall perennial forbs, growing up to 8 feet tall, with stems that are somewhat straw-colored and hollow at the base and a darker bluish color above. They grow from a deep, vertical, woody taproot, beginning growth in late spring, flowering July to August, with seeds maturing from August to September. They reproduce from seeds.
Flowers and Seeds: Light to dark purple-blue flowers with a long spur at the rear. Five sepals, four petals. The two upper petals plus the sepals form the spur. The two lower petals bear deep nectar cups. The flowers grow in dense clusters (raceme) at the top of the stem. Fruits are many-seeded follicles (pods). Seeds are irregularly winged and about 0.08 inches (0.2 cm) long.
Leaves: Divided into sharp pointed segments (palmately lobed), hairy, and resemble geranium in pre-bloom stage.
Tall larkspurs tend to grow on deep soils where a continuous supply of moisture is available and at higher elevations. They grow in mountain meadows on sites where deep snowdrifts persist well into the growing season, under aspens on north-facing slopes, along streams, or around seeps and springs.
Tall larkspurs begin growing as soon as snow melts, but at the upper limits of their distribution, this may not occur until July.
Tall larkspurs can cause heavy cattle losses. Alkaloid concentrations in larkspur vary throughout the growing season. The risk of poisoning depends on how much larkspur is eaten and the concentration of toxic alkaloids, as well as the variation among individuals to tolerate the toxin.
Both palatability and toxicity of tall larkspur increase through the summer, peaking when larkspur pods are abundant. Cattle generally eat little or no larkspur before it flowers. Consumption begins when the flowers are partially or fully open and increases as larkspur moves into pod stage. Leaf toxicity typically decreases with maturity, but pods, which are highly preferred by cattle, contain high concentrations of alkaloids. Producers who observe cattle eating flowers during the early or full flower stages should be aware that this could mean high consumption later in the summer when larkspur pods are abundant.
Losses rarely occur in sheep or horses, but if subjected to sudden physical activity after ingesting large amounts of larkspur, these animals may die.
There is no proven treatment for larkspur poisoning. It has been suggested that poisoned animals be treated with cholinergic drugs such as physostigmine or neostigmine. Though such treatment can reverse some of the clinical changes, their effects on larkspur’s lethal effects are unproven. It may be that the stress and excitement of treatment outweigh any beneficial therapeutic effects. Currently, conservative therapy, such as placing an affected animal on its brisket or chest with its head uphill to reduce bloating and treating bloat, is recommended. Most important is avoiding unduly exciting affected animals until they can clear the larkspur toxins.
Various management strategies may reduce cattle losses to tall larkspur but may require more intensive management for most livestock producers. They include:
L.F. James, R.F. Keeler, A.E. Johnson, M.C. Williams, E.H. Cronin, and J.D. Olsen. Plants Poisonous to Livestock in the Western States. U.S. Department of Agriculture, Agriculture Information Bulletin 415, 90 pp. 1980.
"Reducing Losses Due to Tall Larkspur Poisoning" Fact Sheet. BEHAVE - Behavioral Education for Human, Animal, Vegetation, and Ecosystem Management. 11 November 2009 http://www.behave.net/fact_sheets/larkspur_poisoning.pdf.