Monday, June 24, 2019

Yellow Sweet Clover

Perhaps due to our wet spring, stands of yellow sweet clover are especially large and brilliant along the Front Range this year.  That fact, combined with questioning from a friend, encouraged me to look into the origin and nature of this plant.

Native to Eurasia, yellow sweet clover is a legume and not a true clover.  It is a biennial plant, having a two-year life cycle; during the first year it is low-growing and flowerless while, in its second year, it produces branching stems, up to six feet tall, adorned with racemes of small, yellow, fragrant flowers.  The latter, which bloom from June to September, yield seeds that may be viable for up to 35 years if conditions for germination are not ideal; for that reason, yellow sweet clover is often invasive in areas with poor, dry soil.  A deep tap root also makes the plant drought tolerant and, like other legumes, sweet clover improves soil quality by adding nitrogen to the soil through its root system.

Known to provide large amounts of nectar for honeybees, yellow sweet clover has also been used to stabilize soils and to provide nutritious forage for livestock.  However, this plant contains coumarin, an anticoagulant used in the production of warfarin and rat poison; low-coumarin subspecies have thus been developed for use in hayfields and pastures.