Synthesizing the 2022 Conserving Fragmented Prairies Workshop Part 1 – Prairie Restoration (Reconstruction)

Thanks to everyone who attended the Conserving Fragmented Prairies Workshop last week. We had about 40 participants, representing seven states within the Midwest and Great Plains. I really appreciated the constructive conversations we had about a wide range of topics. As promised, I’m starting to summarize and synthesize the discussions we had during the workshop. In today’s post, I’m starting with the subject of prairie restoration, aka prairie reconstruction. I’ve included a little background and a lot of bullet points below. Thank you immensely to those who took notes and provided them to me.

The only way to defragment fragmented landscapes is through restoration. By converting land around and between isolated prairie remnants, we can strategically enlarge and reconnect those patches of grassland. Larger and more connected prairies are more resilient, as well as being easier to manage – in terms of how careful we have to be not to wipe out tiny populations of plants or animals with management actions.

On the first day of the workshop, we heard from staff of Prairie Plains Resource Institute about the large scale restoration operation they conduct, in which they often plant 1,000 acres or so per year in various locations around eastern Nebraska. They typically harvest 225 to 250 species annually, which is usually split into seed mixes of 100-150 species per site.

Conversation in the seed barn at Prairie Plains Resource Institute. Seeds are laid out and drying. Photo by Michelle Biodrowski.

The Prairie Plains restoration story started with co-founder Bill Whitney’s trip to sites like the University of Wisconsin-Madison Arboretum and the Schulenberg Prairie near Chicago. During the early 1980’s, Bill started harvesting seeds and doing very small experimental plantings in and near Aurora, Nebraska. Over time, he honed his methods and began sharing them with others, including me. When I joined The Nature Conservancy as a land steward in 1997, Bill was a major mentor for me and taught me a tremendous amount about prairies, restoration, and ecology.

To date, Prairie Plains has planted well over 13,000 acres of prairie. They’ve planted on conservation organization-owned land, public agency land, and private land, especially sites with long easements or other legal protections. Working at a large scale forces them to be very efficient with their small staff and limited budget. As a result, they’ve learned a lot that serves as a model for others trying to work at smaller scales. Some of those lessons/tricks include:

  • Keeping a GIS database of harvest locations and dates.
  • Minimal cleaning of seeds. They use hammer mills to break apart pods, etc, but only enough to ensure good seed/soil contact. Leaving lots of chaff in the mix doesn’t hurt anything because of the way they plant.
  • They plant seeds with ‘drop spreaders’ – large old fertilizer spreaders with adjustable holes in the bottom and an agitator inside. They pull the spreaders behind large ATVs and can transport all that equipment on big trailers behind pickup trucks. Small harrows behind the spreaders help ensure the seeds get to soil.
  • They use low seeding rates. Through a lot of experimentation, they’ve found that about 8 gallons of grass seed and 2 gallons of forb seed per acre is sufficient for good results. A gallon of seed weighs about 1 pound.
  • Prairie Plains creates different seed mixes for different soil types and hydrological regimes. They test their seed mixes rather than testing each of the individual species. Testing is done by Colorado State University and includes results for Tetrazolium (TZ) and purity.
Mixing seeds at The Nature Conservancy’s Platte River Prairies seed barn.
A high diversity seed mix that shows both seed diversity and some of the stems, leaves and pods included, but this photo underrepresents how much chaff is included in the mix.
A drop spreader pulled behind a UTV plants seeds on a harvested soybean field. On this sandy soil, and in bean stubble, we’ve found we don’t need harrows. The Nature Conservancy’s Platte River Prairies.

An issue many of us face is that restored prairies often lack strong amounts of early spring wildflowers. That often improves over time as plantings mature, but it can be a particular problem in terms of spring pollinator resources. Most of the issue stems from the fact that it can be difficult to obtain large amounts of seed from early blooming plants, and that problem is exacerbated when working at large scales.

Prairie Plains has been growing plugs of some early species in their greenhouse and then moving plants into restored prairies. They’ve focused heavily on violets because of their tie to regal fritillary butterflies. They dig up small numbers of violets from various site and put them in pots. Plants are allowed to set and drop seed into their pots (screens over the pots prevent the seeds from escaping). Then, the resulting seedlings are moved from those pots into their own ‘conetainers’ and grown into larger plants. In the fall, they transplant the violets from conetainers into prairies in groups of 10, spaced 2-3 feet apart.

Violet (Viola missouriensis) in a pot with seedlings below it. Prairie Plains greenhouse. Photo by Sarah Bailey – Prairie Plains Resource Institute.

Other Topics Discussed (Including Questions Without Clear Answers):

  • It’s a good idea to harvest the same species from multiple sites, if possible. It helps increase (probably) genetic diversity. Is ecological resilience is better built by ensuring a diversity of local ecotypes than by bringing in seed from further distances? (For more on this topic, see this earlier post.) What is an appropriate distance to travel to harvest seeds for a particular project? Prairie Plains uses a rough guide of 100 miles.
  • When harvesting seed from a site, how much of the seed should you take? Fifty percent? More? Less? Does that change if it’s a site that isn’t frequently harvested from? What about small remnants that are neglected and/or likely to disappear? Is there an argument to take all/most of the seed from species in those potentially doomed sites to preserve the genetics of those populations?
  • How does one separate milkweed seeds from the ‘fluff’? Prairie Plains runs the pods through a hammermill. Someone else suggested misting seeds with water and then milling them. You can run the mill in short bursts until the seed separates and then remove the fluff and add another batch. There are also various tools and contraptions that people have built. The Nature Conservancy tried burning the fluff off milkweed seeds, which was fun, but turned out to be counterproductive.
  • Hand harvesting of seeds is the best way to get maximum species diversity but machine harvesting can help increase seed quantities. Some people use combines or pull-behind seed harvesters to harvest groups of species simultaneously and then supplement that with hand harvesting other species. You can run the machines at different times of year to capture whatever seeds are ready at the time, but of course you have to be cautious of harvesting seeds of invasive plants.
  • There was some discussion of how to manage sites to optimize seed harvest. When harvesting grasses like big bluestem and Indiangrass, spring burning helps trigger seed set and is an important way to get good harvests. When dealing with plant species that can have high frequency/abundance of insects that eat the seeds, sometimes grazing, mowing, or burning can help break persistent cycles of that insect granivory. For example, one insect that feeds on Canada milkvetch seeds (Astragalus canadensis) overwinters in the soil below the plants. Grazing a site (and preventing flowering) for a season can break that cycle and buy a year of lower insect numbers. Sometimes burning or mowing – including just mowing the flowers off – can force plants to bloom later and help disrupt insect patterns.
  • Including annual and biennial plants (including ‘weedy’ annuals) in seed mixes can be important. Those species can establish quickly and help pave the way for others. They might also help compete with true weeds that can stifle establishment. Longer term, they play important roles in the way plant communities respond to disturbances like drought, fire, grazing, etc.
  • Years ago, members of the Grassland Restoration Network from around the country arrived at a consensus that although there are lots of ways to successfully establish prairie, one approach that worked consistently for everyone is a broadcast seeding in the dormant season into soybean stubble. If you want to learn more from that network, follow this link to that blog and explore the many topics discussed there.
Former Hubbard Fellow Ashley Oblander harvesting seed with a pull-behind seed stripper. The Nature Conservancy’s Platte River Prairies.

Figuring out the methods that work best at a local site is crucial for success. The methods Prairie Plains and The Nature Conservancy use in central and eastern Nebraska won’t necessarily work well in other places. Seeding rates, weed management, site prep, and other factors are all strongly dependent on local conditions. Whenever possible, a restoration project should be undertaken in stages, using small experimental plantings during the first few years that can guide larger plantings later.

Even after apparently successful tactics have been found, it’s still helpful to experiment by trying something different in small portions of each planting. Those experiments might include variations on seeding rates and species composition, different site prep or weed management treatments, timing of planting or other actions, etc. Recording any differences can help you continue to refine your methods and, more importantly, can help others in your area if you share what you learn.

I’ll talk more about objectives and measuring success in a separate post, but those are important components of restoration projects too. It’s important to know what, specifically, you’re trying to achieve with a restoration project and then think about ways to measure whether you achieved it. Evaluating a project to establish grassland bird habitat might use very different metrics than would be used to evaluate a project to create pollinator habitat or to reconnect two isolated prairies.

For those of you who participated in the workshop, I’d love to have you add to this post by commenting below. What else did you hear? What did you come away from the workshop with that was helpful or thought-provoking? For those who didn’t attend, please feel free to add to the information here or to ask questions that I or others can respond to.

Thanks again to everyone who made the workshop a success!

This entry was posted in Uncategorized by Chris Helzer. Bookmark the permalink.

About Chris Helzer

Chris Helzer is the Director of Science for The Nature Conservancy in Nebraska. His main role is to evaluate and capture lessons from the Conservancy’s land management and restoration work and then share those lessons with other landowners – both private and public. In addition, Chris works to raise awareness about the importance of prairies and their conservation through his writing, photography, and presentations to various groups. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press. He lives in Aurora, Nebraska with his wife Kim and their children.

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