Larkspur (delphinium) is toxic for livestock

This week we are going to talk about delphinium, also called larkspur. We have gotten several questions on this plant last year, especially from farmers and ranchers, as they realize that this plant is toxic to livestock and asked if we go after this one.

This plant is indeed toxic to livestock, but it is not listed as a noxious weed in Washington, so it is not on our list to go after. If a plant is not on our list to control, then we cannot legally enforce control on these plants even though they may be harmful or problematic. We may, however, recommend that they be removed and warn of the potential dangers or problems these plants can cause.

The kind of larkspur we have in our area is the delphinium genus. This is a perennial plant that is in the Ranunculaceae or Buttercup family. One thing that all plants in the Ranunculaceae family share is that they are all toxic. These plants contain alkaloids that are very toxic to livestock, and are also toxic to humans. Larkspur is more common in higher elevation areas and many ranchers delay moving cattle into these areas in late summer when the plants have dried up reducing the toxicity.

Larkspur flowers can vary in color from purple to blue, red or white. The sepals on the flowers fuse together to form a hollow pocket and a spur that sticks out, which gives the plant its name. The leaves are deeply lobed and can have from three to seven lobes in a palmate shape.

So how do we control this plant? Because larkspur is a perennial, the best course of action is to use systemic herbicides that move through the plants and kill the roots. Mechanical control generally does not work well for perennial plants as they have an extensive rhizome system and can come back from even the smallest root fragments. For small infestations mechanical control may work, but for larger infestations it is likely not worth the effort. Likewise, burning is not effective as fire will only burn the tops of the plants but leave the root system intact where it will grow back.

If you have questions about identifying potential noxious weeds or need more information about controlling them, give our office a call at (509)754-2011 Ext. 4710 or visit our website at www.grantcountyweedboard.org.