About Astragalus bisulcatus (Hook.) A.Gray
Growth Form
Astragalus bisulcatus (Hook.) A.Gray is a herbaceous perennial plant with a thick, woody rootstock, growing between 30 and 100 cm tall. It produces numerous simple stems and long pinnate leaves.
Floral Characteristics
Its flowers grow in narrow, elongated racemes, and are either white or purple, blooming in late spring and early summer.
Fruit and Seed Traits
The plant’s seed pods have a characteristic two-grooved structure on their upper surface. Fruits ripen and release their seeds during July and August; the seeds are dark brown or black, reniform (kidney-shaped), 4 mm long and 2 mm wide.
Selenium Accumulation Mechanism
Astragalus bisulcatus accumulates large quantities of selenium when grown on selenium-containing soils. In this plant, selenium replaces sulfur in produced amino acids.
Livestock Toxicity Risk
Most animals avoid this species due to the musky odor of dimethyl selenium compounds in its tissues. However, sheep and cattle may eat the plant, leading to selenium poisoning.
Acute Poisoning Outcomes
Sheep can die within thirty minutes after eating half a pound of Astragalus bisulcatus. In 1907 and 1908, around 15,000 sheep in Wyoming died from either alkali disease or blind staggers, both conditions caused by consuming large amounts of selenium from this plant.
