Early Season Grazing by Cattle of Waxy Larkspur (Delphinium glaucescens) in Central Idaho

Abstract

Toxic larkspurs (Delphinium spp.) in western North America are abundant native plants on foothill and mountain rangelands, typically with showy blue owers. Larkspurs are often divided into three classes depending on the plant height: tall, low, and plains larkspur. Tall larkspurs include four species: subalpine lark- spur (Delphinium barbeyi), duncecap larkspur (Delphinium occidentale), sierra larkspur (Delphinium glaucum), and waxy larkspur (Delphinium glaucescens, sometimes referred to as smooth larkspur). These long-lived perennial plants typically begin to grow in spring under snow banks and continue rapid spring or summer growth when snow banks recede. Tall lark- spurs take about 50 to 60 days to reach mature height from the onset of growth, and they begin to ower when plants have reached about 75% of their mature height. After ower- ing, seed pods begin to form from mature owers. These pods are very palatable to cattle and are often avidly consumed in late summer. After the pods mature, they split open and ma- ture seeds are dispersed. After the pods break open, the plants begin to rapidly senesce.

DOI: 10.2458/azu_rangelands_v35i4_pfister