|Larkspur (Delphinium spp.)|
The larkspurs are divided into three groups: the tall larkspurs (D. barbeyi, D. occidentale), the low larkspurs (D. nelsonii), and the plains larkspurs (D. geyeri), based on their height at maturity and geographic location.
Tall larkspurs have a spurred blue flower, similar to that of garden delphinium. Broad leaves are divided into deep lobes. In contrast, wild geranium, which is often mistaken for larkspur, has shallow leaf lobes. Tall larkspur is a perennial that is found on hillsides and in meadows. It ranges in height from 1 to 2 meters. A hollow stem distinguishes larkspur from poisonous monkshood, which has a similar blue flower but with a hood.
Low larkspur has spurred blue flowers that grow on the top third of a single and unbranched stem. It is found on grassy hillsides and in sagebrush areas, where it may reach a height of 2 feet. Leaves alternate and are divided into deep, narrow lobes. The stem is hollow.
Where and When It Grows
Low larkspurs tend to grow at lower elevations (and higher elevations with tall larkspurs) where they grow, mature, and become dormant before the soil moisture is depleted. They begin growing in early spring, often before other forage begins growth. Low larkspurs are most palatable to cattle after flowering.
Plains larkspurs are found primarily on the high plains of Colorado, Wyoming, and New Mexico. Cattle may eat plains larkspurs at any stage of growth. Both low and plains larkspurs begin growing in early spring, often before grasses start their spring flush of growth. Under these conditions, larkspur may be the only green herbage available to cattle.
How It Affects Livestock
Losses rarely occur in sheep or horses, but if subjected to sudden physical activity after ingesting large amounts of larkspur, these animals may die. Plants are most toxic during early growth, but toxicity gradually declines over the growing season. However, toxin levels may increase in the flowers and pods even late in the season. The toxic substances are mixtures of several alkaloids. These alkaloids and their relative toxicity and concentrations vary between individual plants, at different locations and between larkspur species. The method of toxicity has been identified as neuro-muscular paralysis, leading to respiratory failure, bloat and often death.
All parts of all larkspur species are poisonous, but new growth and the seeds contain the highest concentrations of toxic substances.
Signs and Lesions of Poisoning
How to Reduce Losses
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.
Tall larkspur can be controlled with picloram (0.5 - 1.0 kg ae/Ac) up through the flowering stage. Metsulfuron (30-40 gm ai/Ac) is effective as a spot spray when applied in the early vegetative and bud stages of growth. Follow precautions when handling herbicides.