Larkspur (Delphinium spp) is a genus of about 300 species of perennial flowering plants in the family Ranunculaceae. They are are often sold in nurseries as garden ornamental but also grow in the wild. They are native throughout the Northern Hemisphere and also on the high mountains of tropical Africa.
Larkspurs are poisonous to horses and other animals if eaten. All parts of the plant contain highly toxic alkaloids, with one of the most important being delphinine. The toxin is highest during early growth of the plant, and again once the flowers and pods bloom late in the season. The amount of toxin in each plant varies considerably.
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.