While flowering rush may be a lovely pond decoration, it is also a formidable invasive plant that’s restricting water flow
Flowering rush seems to be an ideal ornamental pond plant. Plants grow on the water’s edge or fully submerged. They are striking, with stalks up to a metre tall, topped by nickel-sized pink flowers. But flowering rush also spreads easily and is hard to kill, making it a formidable invasive species.
Flowering rush can restrict water flow in irrigation canals and through culverts. It makes poor duck habitat and crowds out native species. Invasive species such as flowering rush can also drop land values.
“The people that really stand the biggest threat from flowering rush are lake users and the irrigation infrastructure guys,” says Nicole Kimmel, weed specialist with Alberta Agriculture and Rural Development.
Saskatchewan and Alberta’s revised weed legislation both place flowering rush in the most severe weed class, meaning complete eradication is the goal. But when it comes to reproduction, the perennial is a triple threat. Roots spawn clones. Removing the plant shakes loose bulblets, or miniature bulbs, that float away and generate more plants. New plants also germinate from seeds.
Kimmel knows of five Alberta locations with flowering rush infestations. The Sturgeon River has sporadic infestations spread over six kilometres. Flowering rush also grows near Innisfail, along Isle Lake, in Lake Chestermere and in the irrigation canal that runs from Lake Chestermere.
Kimmel says people have dredged the Lake Chestermere canal with heavy equipment, but it’s too early to know if the dredging has been successful. Officials haven’t tackled river infestations yet because they’re concerned about inadvertently spreading plants downstream.
“So before we get tromping through and pulling plants like crazy, we’re trying to come up with a solution to address that problem, and try and tackle it the best we can without causing more damage than good,” says Kimmel.
Because flowering rush is an aquatic plant, Kimmel says Alberta government officials will be responsible for dealing with infestations in most cases. But farmers with wetlands, creeks or rivers on their land may want to keep an eye out for it.
Flowering rush is easy to identify while flowering. The plants usually flower continuously between early August and the end of September. But if it isn’t flowering, it blends with cattails and sedges.
Though Alberta nurseries shouldn’t be selling flowering rush anymore, the plant is still in landscaped ponds.
“That’s the biggest threat of this spread, that it still probably exists in some pond locations,” says Kimmel.
“It’s in small enough numbers that we definitely stand a chance to eradicate it. But we need to really bump up the awareness (with) the pond people that they are sourcing these outbreaks in the province. So they need to be more diligent in how they handle that material.”
If people are removing flowering rush from ponds, Kimmel says they should keep the plants dry and away from low-lying areas, as they could resprout. Officials don’t know if flowering rush can survive composting, so leaving plants out for compost isn’t recommended.
Flowering rush in Interlake and Winnipeg areas
Cheryl Heming, executive director of the Invasive Species Council of Manitoba, says Manitoba’s flowering rush infestation isn’t yet widespread. The Council has found plants around Winnipeg and in the Interlake region.
Heming says her understanding is the infestation originated in the late 1940s. Flowering rush was brought into the province as a potential garden cultivar. Since then plants have spread through the watershed.
“We actually hope to be working with the Department of Conservation in terms of checking out a couple marshes that (are) attached (to) the Red River because we’re concerned,” says Heming.
City of Winnipeg staffers are experimenting with cutting flowering rush stems to control the plants in a landscaped pond.
Manitoba legislators are currently reviewing the province’s weed legislation. Heming says the Council has recommended flowering rush be listed under proposed noxious weed legislation.
Saskatchewan non-profit develops removal method
There one known flowering rush infestation in Saskatchewan and it’s on the edge of eradication.
Botanists visited the wetland, which is south of Young, in 2004. They confirmed the infestation and clipped seed heads to slow the spread.
Nothing more was done until Chet Neufeld took over as the executive director of the Native Plant Society of Saskatchewan. Neufeld was going through archived files when he found a footnote about the flowering rush infestation.
“And so I thought, ‘Well, if this is the only known location in the province and nobody’s taking care of it, we should do something about it,’” says Neufeld.
At first, Neufeld only had time to clip the seed heads. But in 2010, federal and provincial funding, along with several volunteers, allowed the Native Plant Society to map and remove plants and collect data.
No herbicides are registered for flowering rush, so Neufeld devised a manual removal method that doesn’t spread plants and minimizes reemergence.
“There is only one way at the moment to deal with this, and it’s the hard way. But we’re making a difference,” says Neufeld.
Shovels cut roots, leaving root pieces behind, so volunteers use pitchforks to lever plants from the mud. Entire plants, including soil stuck to the roots, are double-bagged. Volunteers then search the hole the plant was pulled from with their bare hands, feeling for bulblets and root pieces. Finally, they stir the water in the hole and grab any floating bulblets.
Volunteers mark removed plants’ locations with pin flags so they can check them the next year. Neufeld says about 30 per cent of the removed plants reemerge the next year. Reemerging plants are much weaker and don’t come back after the second removal.
This year about 40 volunteers, including local high school students, pulled out all the flowering rush over several weeks. They removed about two tons of material, including plants and soil.
“It was kind of a vicious cycle with just me because all I ever had the time for was just clipping seed heads. I’d get done that, and it would basically start freezing up on me. So I never would have (broken) out of the cycle if it wasn’t for volunteers and for additional funding from the province and from the federal government.”
For the last three years, volunteers have also surveyed 50 nearby wetlands to make sure the flowering rush hasn’t spread (it hasn’t). The Native Plant Society of Saskatchewan will eradicate reemerging plants next year, and then monitor the wetland for several years to make sure the infestation doesn’t reemerge.
The Saskatchewan method likely won’t work for fully submerged plants because of logistics and safety concerns. It would also need to be adapted for flowing water, as the current would carry bulblets downstream. Neufeld says a fine net would need to be set around the work area to catch escaping bulblets. However, it has worked very well at the Young site.
“When we started this project, we were looking at maybe eradicating it within 10 years. I think we’ll be able to do it probably in just over five,” says Neufeld.
Resources to identify invasive species
Neufeld is a biologist and agrologist, and is happy to help farmers identify weeds or forward them resources. Farmers or ranchers can call Neufeld at (306) 668-3940 or email [email protected]
Each province has an invasive species council that has factsheets, reporting information, contact information and other resources. Their websites include invasivespeciesmanitoba.com, saskinvasives.ca, and invasiveplants.ab.ca.
Manitoba’s Invasive Species Council also uploads information to prips.usask.ca.
Alberta and Manitoba residents can see which areas have invasive species at eddmaps.org/alberta. Saskatchewan plans to map invasives through imapinvasives.org. †