Tall Larkspur

April 08, 2011 Print Friendly and PDF
Subalpine Larkspur (Delphinium barbeyi), one of many species of Tall Larkspur, courtesy of Dr. Roger Banner, USU Extension

Scientific Name: Delphinium spp.
Distribution: Western United States and Western Canada
Type of Poison: Alkaloids
Signs of Poisoning:

  • Nervousness
  • Weakness and staggering gait; animal may fall suddenly
  • Salivation
  • Muscular twitching
  • Nausea and vomiting may occur.
  • Bloating may occur.
  • Rapid, irregular pulse
  • Animal may die suddenly; excitement intensifies all signs of poisoning.

Contents

About Low Larkspur

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.

Where and When It Grows

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.

How It Affects Livestock

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.

How to Reduce Losses

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:

Early and late season grazing: Since cattle generally eat little tall larkspur before it flowers, producers may have four to six weeks of low-risk grazing early in the summer. During late summer and fall after seed pods shatter, toxicity decreases and cattle can be moved to larkspur-dominated sites, providing weeks of low-risk grazing while resting other areas of the range.
Herbicidal control: Picloram at 2.2 pounds per acre kills tall larkspur when applied in the vegetative, bud, and flower stages. Control with herbicides is most economical when larkspur grows in dense patches that can be effectively treated. Do not graze cattle on larkspur ranges treated with herbicide until larkspur is senescent in the fall. Herbicide treatment may increase palatability to cattle but does not lower larkspur toxicity. Follow precautions when handling herbicides.
Sheep grazing before cattle: Larkspur is much less toxic to sheep than cattle. Sheep may be used to graze or trample dense patches of tall larkspur, thus reducing availability and/or palatability to cattle.
Aversion conditioning: Cattle can be trained to avoid eating larkspur, and this may be practical if persistent losses occur.

References

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.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.