Butomus umbellatus

Lore & Background

Butomus umbellatus is native to Eurasia and was first found in Canada in the late 1800s and in the United States in the early 1900s. Its name is derived from Greek bous, meaning 'cow' or 'ox', and tome, a cut, referring to the plant's swordlike leaves. Despite its English name, it is not a true rush. The plant grows on the margins of still and slowly moving water and has pink flowers with darker veins. Its leaves are linear, pointed, triangular in cross-section, and arise in two rows along the rhizome. The inflorescence is umbel-like, with a single terminal flower surrounded by three cymes. The flowers are regular and bisexual, with three petal-like sepals and three petals, 6–9 stamens, and superior carpels. The fruit is a follicle, and seeds have no endosperm.

Reader's Guide

Butomus umbellatus is notable for its dual status as an ornamental waterside plant and a serious invasive weed. It was unintentionally introduced into the United States’ Great Lakes through the discharge of contaminated cargo ship ballast water. The plant spreads mostly from its rhizomes and occurs in wet areas with muddy soil, such as freshwater marshlands, lakes, and streams. It outcompetes native vegetation and creates dense root structures that become hazards for boat traffic. Its tolerance of a wide range of temperatures gives it the potential to invade across much of the United States. As a result, it is listed as a prohibited species in Michigan, Minnesota, and Illinois, and as a restricted species in Wisconsin. In parts of Russia, the rhizomes are used as food. In its native range, it can be found locally in Great Britain, for example at the Caldicot and Wentloog Levels.

Did You Know?

• Butomus umbellatus is the only species in the family Butomaceae.
• Its name comes from Greek words meaning 'cow' or 'ox' and 'cut', referring to its swordlike leaves.
• It was first discovered in North America in the St. Lawrence River in 1897.