Bison have been grazing the prairies at Kankakee Sands for two and a half years now, and I still find them as intriguing and fascinating as the first day they arrived. Those stately thousand-pound beasts seem to calmly pass the day, but actually they are very hard at work…with their teeth!

The bison’s grazing habits are why we brought them to Kankakee Sands —to help rejuvenate our prairies by eating the grasses and sedges, allowing the flowering plants to thrive. More flowering plants means a more diverse prairie, which in turn attracts a greater variety of birds, insects and animals.

And those 32 teeth of the bison have been putting a world of hurt on scouring rush, one of our more challenging invasive plant species at Kankakee Sands.

Equisetum at Kankakee Sands

Scouring rush (Equisetum hyemale) is a very old plant, most closely related to ferns, and a relative of plants which grew on earth 350 million years ago. It is a dark green, flowerless, reed-like plant with hollow, jointed stems that grows two to four feet tall. Around each joint is a whirl of very tiny leaves. At the tip of the stem is a light brown, cone-like structure which produces spores, by which the plant reproduces. 

Deep vertical ridges on the stem, easily seen with the naked eye, contain silica making the plant feel rough to the touch. This roughness was quite useful to Native Americans and early settlers who used it regularly to scour and polish such surfaces as wood and metal. 

Though native to Indiana, as well as all of North America, Europe and Northern Asia, scouring rush has become an invasive plant at Kankakee Sands, crowding out other native plants. Scouring rush can take over acres and acres of wet ground via spreading aggressive underground rhizomes. It is so tenacious that I have seen it growing in sidewalk cracks and even pushing up through the asphalt on our Newton County roads!

More common and natural places to find scouring rush are moist, sandy or gravelly areas such as marshes, swamps, pond and lake edges, ditches, seeps, fens, and moist openings in woodlands. 

When my kids and I stumble into a patch of scouring rush growing in the field, we cannot resist pulling the plant apart at the joints. Equally as fun is reassembling the disjointed stems as if they were a puzzle. This action of ripping the plant at the joint is damaging enough to prevent the plant from growing further at that node, which is just fine by me for this invasive plant!  

My kids and I also enjoy walking through areas of scouring rush just for the sound it makes. It sounds like hundreds of snakes swishing through the grass. It’s no coincidence that another name for scouring rush is snake grass. 

Knowing that scouring rush contains silica and is so abrasive, I find it a bit shocking that the bison are eating it. Yet, bison have historically been known to inhabit areas where scouring rush grows. One study in Canada found that their bison spent 20 percent of time in scouring rush infested areas, second only to areas with sedges and true rushes. 

This spring, when we were moving the bison herd from the north pasture to the south pasture, several of our bulls did not want to leave the scouring rush patch north of the Kankakee Sands office. It took several days of encouraging them until they finally acquiesced and abandoned their post. If you were driving along US 41this winter, you may have seen the bison in this scouring rush patch just south of CR 400 N. 

Having our bison consume scouring rush was an unexpected, but very welcome, surprise. We are quite curious to know what effect the abrasive scouring rush is having on the teeth of our bison. Perhaps it is keeping their teeth pearly white and healthy…nature’s toothpaste?

What we do know is that by nibbling down the scouring rush, the bison are creating more room for the 600 + species of plants native to northwest Indiana.  And that is really something to smile about! 

The Nature Conservancy’s Kankakee Sands is an 8,300-acre prairie and savanna habitat in Northwest Indiana, open every day of the year for public enjoyment.  For more information about Kankakee Sands, visit or call the office at 219-285-2184.