Where to Find Remnant and Restored Prairies in Minnesota

A restored prairie at Elm Creek Park Reserve, Maple Grove, MN.

On a windy summer day, a Minnesota prairie looks like an ocean. The tallest grasses move like waves, their stems bending, rebounding and bending again, an imaginary sea of grass. 

For prairie plants, bending without breaking isn’t just a metaphor for survival; it is survival, one of many adaptations for life in a dry, often windy, fire-prone upland. These forces have literally shaped the grasses that dominate the landscape. Their narrow leaves minimize water loss, their low growing points help them recover after fire or grazing, and their deep roots serve to both anchor and absorb. (See this illustration of prairie plant root systems.)

Among the grasses are a variety of forbs, non-woody plants other than grasses. Depending on the site, there may be pasque flowers (Anemone patens), lupine (Lupinus perennis), butterfly milkweed (Asclepias tuberosa), prairie clovers (Dalea species), boneset (Eupatorium perfoliatum), gentians (Gentiana species), sunflowers (Helianthus speces) and many others, each flowering in its own season.

From left: Prairie larkspur (Delphinium carolinianum), butterfly milkweed, and bottle gentian (Gentiana andrewsii).

 
They're all part of Minnesota's northern tallgrass prairie, part of a larger grassland biome in the central United States and south­ central Canada. Northern tallgrass once covered roughly 18 million acres in the southern and western parts of the state. About 235,000 acres remain, less than two percent of the original area.

 

The Minnesota DNR's map of original prairie (yellow) and remaining prairie (red).The original, readable map is here.  

That's not much, but there are still places to find remnants and restorations of this now-limited ecosystem. Here are some resources to help find them.

The Minnesota DNR's Prairie Finder maps public lands you can visit to explore prairies. These are state parks, historic sites, national wildlife refuges and other places where prairie is protected or restored for education, research, and enjoyment. One such place is the Northern Tallgrass Prairie National Wildlife Refuge in western Minnesota. 

The U of M's Minnesota Natural Resource Atlas is an interactive map that allows you to search for native prairies and other natural resources in the state. At the website, select the Interactive Map and choose Add Layers. In the pull-down menu, check the box for Native Prairie in the Biota category and wait for the map to load. Keep in mind that some of the prairies are on private land.

In the Twin Cities area, Three Rivers Park District has restored about 1,600 acres of prairie. Crow-Hassan Park Reserve in Hanover, Murphy-Hanrehan Park Reserve in Savage and Carver Park Reserve in Victoria have the largest holdings. Entry to the parks is free. Public seed collections in late summer and fall help support additional restoration.

This recently burned prairie at Crow Hassan Park Reserve is already growing back, and with vigor. This is lupine, Lupinus perennis.

 
The Prairie Wetlands Learning Center, part of the Fergus Falls Wetland Management District, showcases the eastern-most part of the prairie pothole region, a mix of shallow wetland depressions and upland prairie. Trails are open to the public any time. Call for Visitor Center hours. The Learning Center also offers programs for students and teachers.

If you can't visit a prairie but want to see one, you can go there virtually. Minnesota Scientific and Natural Areas Virtual Visits can take you to several, such as Bluestem Prairie near Glyndon and Lost Valley Prairie near Hastings. The websites for many state parks also offer virtual tours of their lands, such as Buffalo River State Park's panoramic views of Prairie View Trail and Big Sky Trail.

Another option is to view the PBS video Life of a Prairie, about a private, undisturbed prairie in western Minnesota. For a compilation of information about prairies, including some great photography, see the DNR's Prairie Stories. 

Spring ID of Bittersweet Vines

American bittersweet (Celastrus scandens) and invasive round leaf bittersweet (C. orbiculatus) are like identical twins: Only subtle differences tell them apart. 

This is especially true after their leaves have expanded and before they develop flowers. In this in-between time, the vines are practically impossible to distinguish. Both have twining stems with alternate, toothed leaves. Leaf shape is generally round, eliptical or egg-shaped with pointed tips, but their shapes are variable and overlapping. Even the name "round leaf" isn't much help to detect the invasive species, because its leaves aren't always round. 

In spring, though, two characteristics can help with ID: the way the leaves unfold or unfurl from the buds, called vernation, and how the flowers are positioned along the stem. 

Vernation

Inside the bud and as they begin to emerge, the edges of American bittersweet leaves are rolled inward, toward the upper side of the leaf. The botanical term for this is involute. In contrast, the leaves of round leaf bittersweet are folded vertically along the midvein, so the upper sides of the blade face each other. This is a conduplicate pattern. Depending on weather, vernation may happen quickly. Early observations are helpful. 

Left: American bittersweet leaves are involute -- they are rolled inwards in the bud and as they emerge. Middle and right: Round leaf bittersweet leaves are conduplicate -- intially, they are folded inward along the midvein. Photos by Lisa McIntire.

Flower Position

Bittersweet vines typically flower in May and June. The flowers of both vines are about 1/4 inch (5 mm) across and greenish white to greenish yellow with five petals. Male and female flowers are on separate vines.

The difference is the flowers' positions. American bittersweet flowers are clustered only at the ends of stems, whereas the flowers of round leaf bittersweet grow from leaf axils, the areas where leaves join stems.

American bittersweet flowers are clustered at the ends of stems and branches. No clusters grow from the axils. These are male (pollen-producing) flowers. Photo by Peter Dziuk, (c) 2011, from Minnesota Wildflowers. 

Unlike American bittersweet, clusters of round leaf bittersweet flowers grow from leaf axils. These are female (seed-producing) flowers. Photo by K. Chayka, (c) 2013, from Minnesota Wildflowers.

After flowering, male vines can't be identified to species using visible characteristics. Female vines, though, will develop fruits, and they are in the same positions as the flowers: American bittersweet at the ends of stems, round leaf bittersweet at the axils. 

The spherical capsules are initially green, but as the season progresses their walls ultimately turn either orange (American) or yellow (round leaf). In later summer and fall, the capsules split open to reveal red arils, fleshy berry-like structures that enclose the seeds. American bittersweet capsules contain only one seed; round leaf bittersweet capsules contain five. 

Left: Mature American bittersweet capsules are orange, later splitting to reveal red arils. Right: Mature round leaf bittersweet capsules are yellow. These have already opened. Both photos by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org.

Why Early ID Is Important

Round leaf bittersweet is originally from Asia, introduced here for its colorful fruiting vines. It's more aggressive than native American bittersweet and will girdle and smother the trees it grows on. Its dense growth can shade out any plants below. The result is lower plant biodiversity, with consequent effects on insects, birds, and other animals. 

In Minnesota, round leaf bittersweet is listed as a noxious weed, and by law it must be prevented from spreading. Identifying the plant early, especially before it produces fruits, is important to contain its spread. More information is available from the Minnesota Department of Agriculture and the Minnesota Department of Natural Resources. 

Despite control efforts, round leaf bittersweet still finds its way into Minnesota. Seeds are dispersed by birds, and some online sellers will ship seeds or live plants into the state. Mistaken identity can be a problem, too. What's sold as American bittersweet is sometimes round leaf. Look at any photos on the seller's website and compare them to the pictures above. Better yet, if you want American bittersweet, buy it from a reputable, local native plant nursery.

If Round Leaf Bittersweet Is on Your Private Property

The Minnesota Department of Agriculture advises removing the vine but keeping it on your property to decay. Transporting it increases the possibility of fruits and seeds escaping.

If you have a wreath, spray or garland made from real fruiting vines, keep it indoors. Don't toss it outdoors, and don't throw it in the trash. Both will aid its spread. If you want to dispose of it and there is no other round leaf bittersweet on your property, take it to a composting site that accepts noxious weeds (call first) or enclose it in a clear plastic bag and put it in the sun for several weeks to months to kill any viable seeds. Crushing the seeds with a hammer may also be effective.