Flowering rush (Butomus umbellatus)

flowering rushDescription

Appearance

Flowering rush is a reed-like wetland plant with pink flowers.

Leaves and Stem

Leaves are tall, extend from the roots, and are dark green in color. Leaves have a triangular cross-section and tend to twist near the tip.

Flowers

Flowers comprise of three pink petals and three sepals arranged in clusters or umbels (umbrella shaped) on a flower stalk. Flowers typically bloom in June through early fall. Small buds or “bulbils” that form in the clusters of flowers can disperse and grow into new plants.

Seeds

Populations in the eastern United States produce seeds. Only one Minnesota population in Forest Lake (Washington county) is known to produce viable seeds. All other flowering rush populations in Minnesota are sterile and reproduce by vegetative spread, not seeds.

Roots

Roots are bulb-like and appear to “hug” or cup one another. The plant reproduces by vegetative spread from its rhizome (an underground stem that sends out roots and shoots from its nodes) in the form of small onion-like buds (bulbils). Bulbils can detach and spread through water. Individual pieces of the rhizome can break off and also produce new plants.

Biology

Flowering rush is a perennial plant that grows one to four feet high along shores in shallow, slow-moving water. In deeper water, it can grow in a submerged form that does not produce flowers. It flowers in early summer through mid-fall.

Origin and Spread

Flowering rush is native to Europe and Western Asia. The first discovery in North America was in the St. Lawrence River in 1897. The species was unintentionally introduced in to the United States’ Great Lakes through the discharge of contaminated cargo ship ballast water. The species was commonly imported and sold by the water garden trade, leading to the potential for illegal release into the wild. Flowering rush was first confirmed in Minnesota in 1968. Refer to the infested waters list for current distribution.

Don't be fooled by these look-alikes

It is difficult to identify when not in flower, as it closely resembles many native shoreland plants in Minnesota, such as the common bulrush.

Look-alikes:

 

Regulatory Classification

Flowering rush (Butomus umbellatus) is a prohibited invasive species in Minnesota, which means it is unlawful (a misdemeanor) to possess, import, purchase, transport or introduce this species except under a permit for disposal, control, research or education.

 

Threat to Minnesota Waters

Flowering rush causes recreational, economic and ecological damage--changing how residents and visitors use and enjoy Minnesota waters.

Flowering rush impacts:

  • Dense mats at the water’s surface inhibit water recreationists.
  • Overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity.
  • Provides unsuitable shelter, food, and nesting habitat for native animals.

 

What you should do

People spread flowering rush primarily through movement of water-related equipment and illegal release of water garden plants into public waters. The small rhizome buds, or bulbils, can be hidden in mud and debris, and can stick to boots, waders, and other fishing and hunting gear.

Whether or not a lake is listed as infested, Minnesota law requires water recreationists to:

  • Clean watercraft of all aquatic plants and prohibited invasive species.
  • Drain all water by removing drain plugs and keeping them out during transport.
  • Dispose of unwanted bait in the trash.
  • Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.

Follow the “Play, Clean, Go” best management practices to prevent the spread over terrestrial systems.

Report new occurrences of Eurasian watermilfoil to the DNR immediately by contacting your DNR Invasive Species Specialist or log in and submit a report through EDDMapS Midwest.

 

Control Methods

Management of invasive aquatic plants involving either mechanical removal of plants or application of herbicides to public waters requires a permit from the DNR. Talk to a DNR specialist for more information.

Mechanical control can be done by cutting the plant below the water surface several times per summer and removing all cut parts from water. However, in some instances, cutting has facilitated spread. Hand digging is best for small infestations, especially when water levels are low. Hand dig isolated plants with care, as root fragments can spread and sprout.

Herbicide control can be done using imazapyr herbicide. Preliminary testing indicates that a mid-summer application during calm wind conditions may be most effective.

 

Resources