I am writing this from Moorhead, Minnesota, where our crew is attending the annual Grassland Restoration Network workshop. This year’s workshop is being hosted by The Nature Conservancy’s Bluestem Prairie office and others working on prairie restoration in northwestern Minnesota. We spent most of the first day touring Bluestem Prairie, roughly 6,000 acres owned and managed by the Conservancy. There are some gorgeous prairies here, and they have been doing a lot of restoration work to convert cropland back to prairie in and amongst the remnant prairies. Much of that restoration has been accomplished through contracts with Prairie Restorations Inc. (PRI), a private company that has been doing prairie restoration since the 1970’s. Yesterday evening, we toured the local facilities of PRI and saw their impressive array of equipment and seed production plots.
I’ll write more in the next week or two about what we’re learning here, but for today I’ll just mention one big theme that continues to dominate much of the discussion at these workshops: It’s not the seed harvest or planting that limits our capacity to do good restoration work, it’s the management of invasives after planting. As we’ve visited site after site over the years, that topic has remained at the top of everyone’s concerns.
There are basically two ways the issue manifests itself. First, we tend to rush the restoration process and not prepare the site in a way that will help prevent future weed issues. The worst issues usually occur when we are trying to eliminate existing vegetation other than annual crops. Too often, we don’t spend enough time eliminating the grasses or other invasives – and their seed bank – before planting our prairie vegetation. As a result, new plantings have an abundance of weeds that are difficult to control, especially because they’re now mixed in with the new plants we are trying to establish. Investing in several years of herbicide, disking, fire, and/or other combinations of treatments before planting can help eliminate most of the pre-existing vegetation and greatly improve the quality of new restoration sites.
When converting cropland to prairie, many of weed issues have already been dealt with by years of cultivation and weed control, but there are still steps we can take to help deal with potential future invasive species problems. The biggest of those is the elimination of as many invasive species populations around the borders of the restoration site as possible. Investing in the removal of Siberian elm trees, smooth brome, or other nasty plants from field edges can make future weed control efforts much more manageable.
The second major way we get into trouble with invasive species in restoration efforts is that we plant more acres than we can manage weeds on. This often happens because of funding – we get grant money to help pay for restoration work, but that funding usually comes with an aggressive timeline. We commit ourselves to planting a lot of acres quickly and then later realize we’ve just created a massive amount of land that requires invasive species control – which our grant funding doesn’t cover. In some cases we also get into trouble when we start feeling good about our ability to harvest large amounts of seed and figure we should plant as many acres as we can. …and then the weeds show up.
Not all restoration plantings have major invasive species issues, but it’s not always possible to know up front what species are going to be a problem. If bird’s foot trefoil, Siberian elm, or Canada thistle do show up, the best strategy is to get them taken care of when the patches are still small and easy to eliminate. If we’re just dealing with small restored sites, that’s usually feasible. However, when we’re trying to deal with many acres of young restoration plantings and there are small patches of weeds throughout each of them, the problem can become quickly insurmountable.
Invasive species will always be a problem for prairie managers, on both restored and remnant grasslands. However, there are some steps we can take to make our job easier in restored prairies. First, it’s important to take the time to prepare the site ahead of time by eliminating potential invasive problems before planting. Second, regardless of the pressure to move quickly, we have to set the number of acres we restore each year based on our ability to deal with invasive species, not the amount of money or seed we have to do the work.
Ok, time to get back to the workshop. I learned a lot yesterday and hope to learn even more today. Most of all, it’s always inspiring to see how other people are tackling many of the same issues we’re dealing with at home. Even if we can’t provide each other with answers to our thorniest problems, we can at least commiserate about them!