Get reliable science

The many species of larkspur (Delphinium spp.) are among the most dangerous poisonous plants on rangelands in the western United States, causing death losses estimated at 2-5% (sometimes as much as 15%) per year for cattle grazing in larkspur habitat. Other effects, such as altered grazing management regimes and consequent lost forage quantity and quality, are significant but poorly understood. In the face of these consistent losses, range scientists have spent more than a century studying Delphinium species, resulting in significant progress in our understanding of the biology of many species but limited progress on overall losses. Incorporating data from a multi-year, ongoing study in northeastern Colorado, I will discuss the toxicity patterns of Geyer larkspur (Delphinium geyeri), a perennial, constitutively toxic species that declines in toxin concentration throughout the growing season. Evidence from this study points to hypotheses for future research and suggests that the most robust larkspur plants may also be the most toxic. If true, this suggests that current management, which is often aimed at avoidance during high-toxicity periods, may in fact be detrimental. While still in its early stages, this research holds potential to fundamentally alter our understanding and management of larkspur on western rangelands.