Butomus umbellatus (Flowering Rush)
|Also known as:
|Butomaceae (Flowering Rush)
|sun; water to 6-ft depth; marshes, ponds, lakes, rivers, mudflats
|June - August
|3 to 4 feet
|Wetland Indicator Status:
|GP: OBL MW: OBL NCNE: OBL
|MN county distribution (click map to enlarge):
|National distribution (click map to enlarge):
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Convex cluster (umbel) of ¾ to 1¼-inch flowers on stalks 2 to 4 inches long. Flowers have 3 pink, oval to egg-shaped petals alternating with 3 shorter pink to greenish, more lance shaped sepals. The 9 stamens are deep pink to red until they mature and release the yellow/orange pollen. In the center is a whorl of 6 styles fused at the base. Several papery bracts surround the base of the cluster. The cluster is at the tip of a long, sturdy stem with buds developing and opening throughout the season creating a mix of maturing seed capsules, open flowers and small embryonic flower buds present at the same time.
Leaves and stems:
Leaves are basal, submersed in deeper water and emergent in shallower water. Emergent leaves are generally ½ to 2/3 the height of the flowering stem, the blades slender, may be twisted to some degree, erect and grass-like to the casual observer but the blade is conspicuously ribbed along the mid-vein on the underside and triangular in cross section. Both stalk and blades are glossy surfaced.
Flowering Rush is a native of Eurasia first found in North America along the St. Lawrence Seaway over a century ago. Since then it has spread through the Great Lakes and inland all the way to the Pacific coast and was first reported in Minnesota in Anoka County in 1968. A serious wetland invasive species, it chokes out shoreline species both in and out of the water. When not flowering it is difficult to identify, as it closely resembles a number of native wetland species, such as common bullrush, but of special note is the twisting of emergent leaves. This trait was observed in a local population but not mentioned in any references so was considered an anomaly until I came upon the species description at Finland's Naturegate web site, at the bottom of the page.
Flowering Rush spreads primarily by rhizomes, but also by tubers transported by wildlife, bulblets formed in the flower clusters transported by water and wildlife, and occasionally from seed (most seed produced in MN populations is not viable). However, it is the unethical sale and distribution of it by the gardening industry that greatly multiplies the risk of spread. While unlawful to posses or distribute in the State of Minnesota, there is little or no oversight of internet sales and too few customers take the time to inform themselves of the environmental hazards of non-native species. The Minnesota DNR tracks all reports of this pest and some efforts are taken to reduce its impact but there is no statewide control program at this time. Once established there are few effective measures for its suppression or eradication. Mechanical and manual harvesting and herbicide treatments can reduce its numbers but so far has not been able to wipe it out. It is so bad in Detroit Lakes that it must be dredged periodically (no small expense) to keep the public beach open and accessible.
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- Flowering Rush plants
- Flowering Rush infestation all along a pond edge
- more flowers
- piles of mechanically harvested Flowering Rush at the Detroit Lakes city beach
- large, spreading infestation of Flowering Rush
Photos by Peter M. Dziuk taken at a small residential pond in Lino Lakes, Anoka County. Other photos courtesy the Minnesota Department of Natural Resources.
Have you seen this plant in Minnesota, or have any other comments about it?