Invasive Species Council of Manitoba: Flowering Rush

Flowering Rush

Flowering Rush Butomus umbellatus

Found in many aquatic areas in southern Manitoba, flowering rush is a perennial with grass-like leaves similar to bulrushes.

Regarded as one of five invasive alien plants having a major ecological impact on naturale cosystems in Canada and considered a high priority species for eradication in parts ofOntario.

Flowering Rush was most likely introduced into North America via ballast of trans-Atlantic ships and intentional plantings by gardeners.

Description

Flowering Rush invades aquatic and wetland areas including streams, rivers, lakes, stormwater retention ponds, marshes and gravel pits as well as road side ditches.

Flowering Rush grows as an emergent on wet soil or in shallow water however can also grow as a terrestrial plant and or as a submersed plant (Perleberg 1994).

Emergent stems range from 0.5 to 1.5 meters in height and are round in cross section. Stems are green and resemble bulrushes. Best identified by its three-angled leaves and umbel shaped cluster of pink flowers. Flowers are pinkish white grouped in an umbellate-shaped inflorescence at the top of the stalk. Flowering between May and September, it is very hard to identify until flowering.

Ecological Damage

Flowering Rush can displace native vegetation such as wild rice and cattails reducing the overall biological diversity of an ecosystem. It some areas it has impeded irrigation canal systems.

Dense mats of Flowering Rush restrict light, dissolved gases, and nutrients available to other submerged plants. Capable of dominating wetlands displacing native flora and fauna. Often occurs in wetlands with Purple Loosestrife with Flowering Rush dominating shallow areas and Purple Loosestrife dominating open water areas.