A big topic of conversation at this year’s Grassland Restoration Network (GRN) workshop had to do with designing seed mixes to combat potential invasive plant problems. When converting cropland to prairie vegetation, the first few years of establishment are sometimes a race for dominance between prairie plants and invasives. Once a strong native plant community becomes established, it is more difficult (but still possible) for invasive plants to become dominant, so those first few seasons are critically important. Over the years, a number of people have tried using extra high seeding rates of various native plants to see if those natives could help stave off invaders. In an ideal scenario, a high abundance of some showy wildflower would outcompete invasive plants but allow other native plants to establish. Nice, right? Lots of pretty flowers during establishment, no invasive species to worry about, and a nice diverse prairie community in the long run.
I first heard about this idea at the 2004 North American Prairie Conference. In one of my favorite presentations of all time, Shawn Schottler of the Science Museum of Minnesota compared various plant species to celebrities. As he described his experiments, he said he was trying to find Chuck Norris plants (tough good guys) that could fight off Mike Tysons (aggressive invasives) while still allowing Patsy Clines (less competitive natives) to establish. As I recall, he was having some luck with Chuck Norris species such as black-eyed Susan (Rudbeckia hirta), wild bergamot (Monarda fistulosa), and others. At this year’s GRN workshop, Jack Norland of North Dakota State University described recent results of some similar experiments on U.S. Fish and Wildlife restoration projects. The “spike” treatments they used consisted of ultra high seeding rates of species such as plains coreopsis (Coreopsis tinctoria), purple prairie clover (Dalea purpurea), Canada wild rye (Elymus canadensis), and others. His data showed Canada thistle to be much less abundant in spike treatments than in the controls.
Interestingly, we’ve had some accidental experience with this topic here in our Nebraska Platte River Prairies. During the drought years of the early 2000’s, some of our prairie plantings ended up with lots and lots of Canada wild rye. In some cases, the species was so abundant that our plantings looked like wild rye monocultures. We weren’t the only ones. Prairie Plains Resource Institute had plantings that looked much the same during those years. There was some hand wringing about whether or not the plantings had failed, especially given the drought conditions at the time, but Bill Whitney of Prairie Plains assured us that it wasn’t a big deal. He was right, as usual. The plantings eventually emerged from their wild rye phase and turned into very nice prairies. In fact, our site that had the “worst” wild rye infestation is now the showiest (in terms of big colorful wildflowers) prairie we have. I’m not sure the wild rye helped suppress any invasive species, but a high density of wild rye plants didn’t seem to keep Patsy Clines from eventually thriving.
Spike treatments/Chuck Norris species/etc., are really just variations on the idea of using a cover crop – planting something intended to establish early and then fade away (mostly or completely) as the desired vegetation takes hold. In some places, cover crops are very useful in agricultural systems as a way to prevent soil erosion and loss of fertility, suppress weeds, and/or preserve soil moisture. It seems logical that they would also help with prairie restoration establishment. In fact, I recently talked to someone with the Natural Resources Conservation Service (NRCS) in north central Nebraska who says their best successes in restoring sandhill prairie come when they use a cover crop of millet.
On the other hand, I remember a GRN workshop about five or six years ago when we had a group discussion about our experiences with various cover crops. Participants from across the Central U.S. seemed to reach consensus that cover crops were as likely to be counterproductive as helpful to prairie restoration efforts. This seems to conflict with the successes seen by people like Shawn Schottler, Jack Norland, and others. Why the differences?
Part of the issue is certainly that we’re still experimenting with different species, and still have a lot to learn. Beyond that, though, anyone who has spent many years restoring prairie knows that establishment results can be very difficult to predict, even within the same site. Just when you think you’ve got something figured out, your next planting turns out completely unlike what you’d expected. Those kinds of inconsistencies, combined with differences in site attributes such as soil texture and fertility, rainfall, and latitude make it almost impossible to come up with restoration recommendations that apply everywhere. In fact, if we’ve learned anything through the Grassland Restoration Network, it’s that it’s important to start big projects by doing some small experimental plantings to see what works best in that place before investing in larger scale work.
Clearly, the idea of “spike” treatments and similar strategies hold a great deal of promise if they fulfill their promise of preventing invasives while facilitating establishment of diverse plant communities. However, since it’s also clear that successful strategies from one site don’t always translate well to others, we may each have to find our own formula for success. Hearing about Dr. Norland’ experiments in the Dakotas has inspired us to do some more experimentation here. Maybe we can find a few Chuck Norris species to keep the peace in our Platte River Prairies.
If you’ve had positive or negative experiences with cover crops in prairie restoration, or have found your own Chuck Norris of the prairie, please share what you’ve learned in the comments section below. Thanks.
P.S. You may have seen or heard some of the many Chuck Norris jokes out there that play on the idea that he is seemingly invincible. My 14-year-old son likes to share them with me now and then. A few of my favorites are:
Chuck Norris doesn’t wear a watch. He decides what time it is.
Chuck Norris makes onions cry.
There used to be a street named after Chuck Norris, but it was changed because no one crosses Chuck Norris.
When Chuck Norris does a push up, he isn’t lifting himself up, he’s pushing the Earth down.
A bulletproof vest wears Chuck Norris for protection.