They are found in plants in the Delphinium spp. Larkspurs kill more cattle in the United States yearly than all other poisonous plants combined. Description and distribution Larkspurs are the primary source of plant poisoning of cattle on the western ranges of the United States. Larkspurs are grouped by their heigth. They are one of the first plants to emerge in the spring, even when there is still snow cover, and hence, appear inviting to cattle hungry for green vegetation.
Early spring is when poisonings due to low larkspurs are most likely to occur.
They can be found in alpine meadows or under dense tree cover in aspen and pine forests and are very palatable to cattle. Calves tend to congregate under tree cover while the mature herd is out grazing. Because of their small size, calves are particularly susceptible to poisoning from the larkspur patches found in the woods. Where poisons are found in plant Larkspurs alkaloids are concentrated in the growing tips and new leaf growth of the plant. Therefore, larkspurs tend to be most poisonous in early spring, gradually drop in toxicity throughout the growing season, and severely decrease in toxicity following flowering.