Management and Control
Apparently little attempt has been made to control flowering rush in natural habitats in North America (White et al 1993). Control of even small populations can be difficult, as bulbs or rhizome fragments left in the substrate can quickly regrow. As with invasive plant prevention and control in general, leaving the native plant community intact can go a long ways towards preventing the establishment and spread of flowering rush.
The best way to prevent the spread of flowering rush is to avoid planting it. After a day out on the lake, boats and equipment should be cleaned thoroughly, and bait buckets and live wells emptied well away from water. If at all possible, everything should be allowed to dry completely before heading out to the next lake.
Manual Control
Pulling or digging: Flowering rush produces numerous bulblets along its rhizomes, which readily detach when disturbed. Each bulb can produce a new plant. Rhizome fragments can also produce new plants. Therefore pulling is generally not recommended, unless a serious attempt is made to remove all the underground fragments. Digging might be appropriate for patches on exposed wet ground, where there is no immediate danger of bulblets or rhizomes floating away.
Cutting: Cutting flowering rush patches can be an effective means of control (MNDNR 1999). Several cuttings spaced through the summer is most effective at limiting spread and preventing seed set. Most of the rhizome growth occurs late in the season, so cutting the shoots off at this time may reduce vigor the following year (Hroudova et al.1996). Repeated cutting will significantly weaken the plants (Hroudova et al.1996).
Along rivers and other flowing waters, the MNDNR (1999) suggests treating small patches downstream of larger patches first, and working upstream.
Chemical Control
Herbicides are difficult to use on flowering rush, as they tend to wash off the plant's narrow leaves (MNDNR 1999). If control with herbicides is attempted, care should be taken to avoid spraying surrounding (and competing) vegetation. Any attempt to control flowering rush in aquatic habitats must be done using herbicides formulated for use over water. Permits are required for herbicide application over water in many states, including Wisconsin, Michigan and Minnesota.
Cultural and Biological Control
Grazing: At least in Europe, ducks are known to graze significantly on flowering rush, and appear to be a significant controlling factor on flowering rush populations (Hroudova et al.1996). While there is no evidence so far that wild ducks are controlling flowering rush in North America, in habitats such as farm ponds, etc., where domestic birds could be concentrated and subsidized with artificial feeding, this approach might be effective.
Biocontrol: Research into insects and disease organisms that infest flowering rush in its home range, and that might also control it in North America, has so far not been attempted. The fact that flowering rush has no close relatives suggests that it might be a good candidate for biological control.
For More Information
TNC Wildland Weed Management and Research Library
Wisconsin Manual of Control Recommendations for Ecologically Invasive Plants (online)