Pretty Flowers, Deadly Consequences: Poisonous Range Plants in Montana
By Rachel Frost, Post Doctoral Range Research and Extension Associate
Spring has arrived, bathing the rangeland in green and dotting the pastures with wildflowers. While most are innocently beautiful, a few harbor deadly poisons behind their showy flowers. Exotic weeds are often touted as being toxic, however, the most dangerous poisonous plants are native to the state and occur naturally on rangeland. A few of the most common Montana range plants that are poisonous to cattle include:
Low larkspur (Delphinium bicolor) is a low growing, perennial forb with showy blue flowers with a long spur. The plant initiates growth early in spring and is most toxic during its early growth stages. Signs of poisoning include nervousness, stiffness, staggering, and falling as the front legs frequently give way. The toxicity of the plant declines rapidly as plants mature, and poisonings rarely occur after the plants have flowered.
Tall larkspur (Delphinium occidentale) is a large, erect perennial for that can reach 3-7 feet in height. The flowers of tall larkspur are white to light blue and the plant is easily identified by its hollow stem. Poisoning from tall larkspur occurs most often in midsummer when the plant is flowering. Cattle losses may be more prevalent in early fall when snow storms cover up more desirable forage. The signs of poisoning are the same as for low larkspur.
Several species of lupine (Lupinus spp.) are abundant throughout Montana. The most common impact of lupine on cattle occurs when pregnant cows consume sub-lethal quantities and give birth to calves having marked congenital deformities. This syndrome is known as “crooked calf disease.” Almost all cattle losses occur under circumstances where animals consume large quantities of mature (podded) lupine in a short time period. Managers should avoid grazing cattle in pastures where lupine is prevalent and other forage is limited.
Locoweed (Astragalus and Oxytropis spp.) plants derive their name from the Spanish word “loco” which means crazy. Poisoned animals commonly display strange behavior including, loss of muscular control, shying at familiar objects, jumping imaginary hazards and violent actions when disturbed. Locoweed is poisonous at all stages of growth with the greatest losses occurring in the spring when other green forage is limited. Although it has not been proven, many people suggest that animals once poisoned are addicted to locoweed and will actively seek it out on rangeland.
Despite research and educational efforts, poisonous plants remain a serious problem facing ranchers in Montana. This is largely because the circumstances surrounding livestock poisonings can be very different from year to year and from plant to plant. Consequently, no single management strategy can prevent losses to poisonous plants. However, there are a few general management techniques that can greatly reduce livestock losses from poisonous plants:
- Do not overgraze rangeland. Many poisonous plants become more prevalent as rangeland condition declines.
- Be cautious when introducing new livestock to your ranch. Cattle that are from another area may not be familiar with some poisonous plants and are more likely consume those plants.
- Do not turn hungry cattle into pastures with dense populations of poisonous plants.
- Provide adequate quantities of salt and other necessary minerals.
- Provide plenty of clean water to help dilute toxins.
- Do not feed hay containing poisonous plants to livestock.
- Be aware that snow or other environmental conditions can change the way cattle forage, increasing the chances of poisoning.
- And lastly, know the poisonous plants on your ranch and watch those plants for evidence of grazing. Also know the symptoms and signs of toxicity so early treatment can be administered and losses minimized.