Tall larkspurs kill more cattle on mountain rangelands than any other plant or disease. Tall larkspurs are principal components of tall forb communities and occur in patches associated with snow drifts in mountain big sagebrush, aspen and subalpine plant communities. Controlling larkspur patches can substantially reduce cattle deaths (3). Larkspur will never be eradicated, but if its density could be reduced to where a cow could not eat enough larkspur, fast enough, death losses can be reduced.
Ralphs, M.H.; Nielsen, D.B.; Evans, J.O.; and Call, C.A., "Herbicide Control of Tall Larkspurs on Mountain Rangeland" (1999). Archived Agriculture Publications. Paper 9.