- Distinguishing features
- Larkspur are mostly perennial herbs with palmately lobed or palmately divided leaves, the lobes or divisions themselves lobed or divided; the flowers are in a raceme above the leaves, often blue, purple, or white, with a prominent spur formed from one sepal and two petals. A major cause of cattle losses in some portions of the Great Plains and Rocky Mountains.
- The plants, which belong to the Ranunculaceae family, are erect and range from 0.3-1.5 meters in height. The alternate leaves are palmately lobed and veined, similar in appearance to buttercup leaves (also members of the Ranunculaceae family). The striking blue flowers with a prominent “spur" are borne on a terminal stem.
- Geographic range
- Tall larkspurs (D. barbeyi, D. occidentale, D. glaucum) grow primarily at high altitudes (6000-11,000 feet) in moist areas, often under or near stands of aspen.
- Low larkspurs (D. bicolor, D. gyeri, D. nelsonii) grow at lower elevations in open areas and grasslands. Horticultural varieties are widely grown as ornamental garden plants.
- Toxic principle
- Polycyclic diterpene alkaloids, neuromuscular blocking agents that affect cholinergic and nicotinic receptors, are the toxic principle in larkspurs. Alkaloid content can vary considerably with the species and stage of growth. All species should be considered toxic.
- The plant is toxic during the entire growing period. Dosages as low as 0.5% - 1.5% of body weight may be toxic or lethal to cattle and mortality is relatively high among poisoned animals. Cattle are considered much more susceptible than sheep or horses.
- Clinical Signs
- Sudden onset of excitability, disoreintation, muscle tremors, stiffness and paresis. Affected animals may bloat or attempt to vomit which can cause aspiration pneumonia. Cardiac arrhythmias may be present. Signs progress to severe weakness, prostration and seizures. Death results from respiratory paralysis.
- Laboratory diagnosis
- not useful.
- congestion and bloat may be all that is noted.
- Prompt GID
- Relieve bloat
- Physostigmine is useful in reversing neuromuscular blockade.
- Larkspur are palatable and are readily eaten in the spring when other forage may be scarce. Thus, limiting access early in the season is suggested. Provide adequate free choice mineral supplementation including dicalcium phosphate. Wide-scale control and elimination of larkspur is impractical.
The high calcium content of larkspur (2 to 3%) might partially explain why cattle seem to eat larkspur selectively when they have been on diets marginal in calcium.
Read more in the Poisonous Plants of Pennsylvania Publication