Scientific Name: Delphinium spp.
Distribution: Western United States and Western Canada
Type of Poison: Alkaloids
Signs of Poisoning:
Growth Characteristics: A number of species can be categorized into the low-growing larkspurs. They are short perennial forbs with extensively branched, fibrous to slightly fleshy root systems. Low larkspurs begin growth as soon as the snow melts in the spring. They flower June through July and reproduce mainly by seed but may reproduce vegetatively.
Flowers and Seeds: Light to dark purple-blue flowers with a long spur at the rear. Five sepals, four petals, two of which are whitish, giving the flowers the bicolored appearance. The two upper petals plus the sepals form the spur. The two lower petals bear deep nectar cups. There are usually less than 15 flowers per plant, and they are only found on the top third of the stem. Fruits are many-seeded follicles (pods). Seeds are irregularly winged and about 0.08 inches (0.2 cm) long.
Leaves: The small number of leaves are alternate and greatly reduce in size as they extend up the stem. Leaves at the base of the plant have petioles up to 7 cm long, with blades divided into narrow lobes.
Stems: Usually solitary, 4 to 16 inches tall (10 to 40 cm), finely hairy, usually unbranched and hollow.
Low larkspurs begin growing in early spring, often before grasses start their spring flush of growth. Under these conditions, low larkspur may be the only green herbage available to cattle. It is seldom eaten after it reaches maturity, which generally occurs in late June.
Low larkspurs can cause heavy cattle losses. It is highly palatable to cattle, especially after it flowers, and losses can be expected when cattle are allowed to graze larkspur-infested rangelands. This is especially a problem where the plant is abundant or grows in large, dense patches.
Losses rarely occur in sheep or horses, but if subjected to sudden physical activity after ingesting large amounts of larkspur, these animals may die.
All parts of the plant are poisonous, but new growth and the seed contain the highest concentrations of toxic substances. Normally, seeds do not pose any special problem if cattle have grazed the area prior to seed maturity; however, under a rest-rotation system, where cattle enter an ungrazed unit after seeds have started to mature, losses can be significant.
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 are recommended. Most important is to avoid unduly exciting affected animals until they can clear the larkspur toxins.
Larkspur in its early vegetative growth stage is not palatable; therefore, grazing early before plants flower may be a useful option in some areas. Once plants begin flowering, keep cattle off ranges until the plants mature, then allow them to graze larkspur areas after the pod stage when toxicity is low. Using sheep to graze or trample larkspur patches ahead of cattle grazing may also reduce cattle losses. Aversion conditioning can be used to condition cattle to avoid eating larkspur and may be practical if persistent losses occur.
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.
Research results show that low larkspurs can usually be controlled by applying 2,4-D at the rate of 2 kg ae/ac when the vegetative development approaches its maximum but before the first flowers open. Follow precautions when handling herbicides.
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.
Pratt, Mindy S. Low larkspur. Draft. Range Plants of Utah. 2008. Utah State University Extension Service. 30 July 2009. http://extension.usu.edu/rangeplants/