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
Tall larkspurs tend to grow on deep soils where a plentiful supply of moisture is available and at higher elevations (above 7000 feet). 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 the snow melts, but at the upper limits of their distribution this may not occur until July.

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
Larkspur causes heavy cattle losses in western range states. Larkspur is highly palatable to cattle, and losses can be expected when cattle are allowed to graze larkspur-infested ranges, especially where the plant is abundant or grows in large, dense patches. Tall larkspurs increase in palatability as plants mature. Cattle consume larkspur most often after plants begin flowering; consumption increases into the pod stage. Rain, cold fog, or snow showers may lead to greatly increased consumption of larkspur.

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