Some Basic Guidelines for Tallgrass Prairie (and Pollinator Habitat) Seed Mixes

I’ve seen a lot of prairie plantings. Many look reasonably good, a very select few are diverse and complex to the point they resemble remnant prairies, and a good number are little more diverse with native species than an abandoned agricultural field would be after a few years. Most abandoned fields will grow some asters (especially frost aster, panicled aster, and New England Aster), goldenrods (especially tall, Canada, grass-leaved, and giant goldenrods), and common milkweed after two to three years. If openness is maintained, fields may ultimately be colonized by, bergamot, native sedges, self-heal, and others. These meadows have value for pollinators and other wildlife. Prairie plantings, where investments have been made in preparation, seeds, and hopefully subsequent stewardship, should aim higher.

This prairie planting in Iowa is several years old. It differs from remnant prairies in the scarce representation of early-flowering species, which are more difficult to collect in large quantities, but it’s small scale richness and floristic quality (weighted mean C) are similar to nearby remnants. Long-lived prairie forbs are quite abundant, though they are primarily those that bloom in the middle and late part of the growing season.

There will be some specifics in this post, but I’m more interested sharing some guiding principles. All of this assumes good site preparation and subsequent stewardship.

Creating a diverse, complex prairie planting that will be resistant to anthropogenic stressors ranging from climate change to invasive species is no simple task. The prairies that Europeans destroyed developed over thousands of years, with their component parts arriving (and sometimes arriving and departing…and arriving) each at their own pace according to their responses to conditions in North America over thousands of years. The species composition of an old-growth, remnant prairie should not be taken to suggest that a seed mix with the same composition will lead to a similar outcome.

For the following, I will assume that the land steward is making a long-term investment to help heal the land. The planting is not intended to be part of a shifting mosaic working lands destined to be brought back into cultivation within a decade or two. The steward wishes for a legacy not just of cleaner water or more wildlife on the landscape, but more life, complexity, and beauty on the focal property, and the steward dreams of what would emerge and the landscape if others did the same with their land. Biodiversity and the intrinsic value of all parts as essential to the whole are at the core of the steward’s ethics.

I also assume that the planting is not immediately adjacent to an existing high quality remnant. If it is, than the seed mix design should be heavily influenced by the goals set forth in a management plan for the remnant, and species selection and seed sourcing require more nuanced consideration.

I’ll start with what not to do. These are the actions that lead to outcomes that differ little from the alternative of simply allowing a fallow field to begin succession, or which yield warm-season grass over-dominance.

  1. Do not boost amounts of early-maturing, showy species for a big show in the early years. Those species are great for the bees and the butterflies for a few years, but we’re in it for the long-haul, and those species aren’t just a flash in the pan, they will actually diminish the initial establishment of the real long-term doers when it comes beauty and function in the prairie planting. In 10 or 20 years, we want a lot of false indigos, lead plant, compass plant, prairie clover, blazing stars, butterfly milkweed, and on and on. Some stewards achieve blue-eyed grass, wood betony, wood lilies, and prairie phlox! Many plantings only utilize species that peak early like false sunflower, black-eyed Susan, yellow coneflower, and bergamot; these also tend to be the species that can meet conservation standards for the lowest prices. Such plantings are usually over-dominated by grass and forb-poor by the time they are a decade old. The grass itself is good habitat for some species, but it could have been better, and it’s a problem that is difficult to undo without starting from scratch. I’m not saying not to use those early-maturing species, but they should be small components in the seed mix…enough to ensure they establish, but not so much they run rampant in the first three years. This would mean planting things at rates of a 1/64 oz. per acre that are more often planted at a rate of ounces or even pounds per acre. Their negative impacts can be lessened by growing season mowing/haying during years two and three, but that defeats the point of including them in large amounts by preventing their flowering, and there can be more impacts from mowing on ground-nesting birds.
  2. Do not use the big grasses (big bluestem, indiangrass, and switchgrass); at least don’t use them in greater than trace amounts. They often show up regardless as minor contaminants in other seed. These grasses simply establish and occupy real-estate too quickly, and if they establish early in large numbers they prevent slower-developing, desirable species from becoming established in the first place. Even before they flower for the first time, they are reaching out laterally with their rhizomes.
  3. Do not put up too many constraints when it comes to species and seed source selection. Prairie plantings go into altered soils in landscapes containing newly added species, all under a changed (we’ve already shifted things a couple hundred miles) and rapidly changing climate.
  4. Do not introduce seed only once. It’s true that there are diminishing returns later, but there are a lot of valuable species that simply don’t seem to like establishing on the freshly prepared seed bed. Many of these species are the early bloomers and the partially parasitic (hemiparasitic) species that provide critical early resources to pollinators and just might be the glue that holds the high small-scale diversity of tallgrass prairie together.

Instead, do the following.

  1. Do make a long-term investment in the seed mix, and plant 50, 100, or more species. Don’t plant pounds of common milkweed. Plant ounces of butterfly milkweed (or whatever more conservative milkweed is site-appropriate) and a fraction of an ounce of common milkweed. Plant more sky blue aster than New England Aster. Plant a little stiff sunflower, and plant trace amounts of early sunflower. If this means planting just a few acres at a time, do that. Weather can have a big impact on establishment, so it’s probably best to do a little at a time anyway. Buy what you can afford. Collect and add whatever you can. Serious effort in a small area can yield valuable seed for future efforts.
  2. Do use bunch grasses and sedges (graminoids). Many old-growth prairies are dominated by species other than the big, rhizomatous grasses anyway. Clumping species like prairie dropseed, rough dropseed (eroded, overfarmed soils), little bluestem, prairie wedgegrass, Junegrass, and plains oval sedge should be mainstays. Rhizomatous species should be lower-growing and less aggressive, like side-oats grama. Graminoids should be no more than half of the seed mix by weight, but they are essential for the development of fuels that will carry the fires, which are themselves part of the prairie system.
  3. Do use a wide range of species and genotypes that are native to prairies regionally (perhaps level II Omernik ecoregions). Use what is locally available. Use species that should be well suited to site conditions, even if they have to be sourced from farther away. Draw seed for individual species from multiple sources, both as local as possible and farther afield. Push the ranges of species, especially those from within a couple hundred miles to the south, so long as they were/are part of similar prairie systems, because odds are you’re in their climate envelope now or you’re about to be. Very little is actually pinned down about local adaptation in the context of restoration/reconstruction. Research has focused on plant size, seed set, genetic differences, morphological differences, etc. and almost universally sidesteps what is critical for at least the long-lived prairie species, and that is their initial establishment and subsequent year to year survival rates, which are what drive their establishment and persistence/population growth. The results that are out there are mixed. I believe variation in the context of all of the change and fragmentation on the landscape is the most prudent course. What does that look like? Well, I wouldn’t shame a planting for having rosinweed north of its pre-European range. A project might source seed from one producer or another, and the seed might not be super local, but the steward might manage to collect and add some local seed, and the steward might deliberately bias the acceptable seed source region a bit to the south, and that might mean sourcing more southern species as well as genes, so long as they come from similar communities and share recent co-evolutionary histories with the local flora and fauna.
  4. Do keep seeding. Any good plan is going to see to it that a planting is burned as early as it has the fuels to carry fire and frequently, if not annually, for at least several years after. Whenever it is possible to burn in the fall, over-seeding with species that initially failed or which weren’t included initially should occur, even if just small amounts are available, and this should probably continue indefinitely, given the fragmented state of the wider landscape. Partially parasitic species like wood betony should be added during this time. If the steward is thinking across generations, species typical of remnant prairies, but which are difficult to acquire seed from (or grow from seed) may even be planted out as nursery-propagated transplants and tended to until they become established, things like prairie rose, hoary puccoon (now at least one producer is growing this species from seed and selling it in pots), Mead’s sedge, and wild strawberry.
  5. Do keep records of what was planted where, when, how much, and from what source(s).
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Army Lake Oak Woodland

In 2016 I was part of an environmental assessment at the site of the Wisconsin Department of Natural Resources (WDNR) planned boat launch to Army Lake in Walworth County, Wisconsin. My heart sank at the time, because I knew the site. It held the last best remnant of oak woodland acre for acre of any site in southeastern Wisconsin. Just why the woodland there remained in such good condition while the surrounding upland areas became choked with buckthorn, bush honeysuckle, and Asian bittersweet is a matter of conjecture, but it just might be that this island escaped the hard grazing of the early 1900s. There are other such islands, and while not quite so jaw-droppingly intact, they all tend to be in better shape than nearby uplands.

This oak woodland at the site of the Army Lake boat launch looked like this when I visited in 2016. It hadn’t been burned; brush had not been cut. It persisted in this state while nearby uplands were overwhelmed with invasive woody plants.
This is the herbaceous layer in May, 2016. Hyposis hirsuta, Luzula multiflora, Carex siccata, Pedicularis canadensis, Erigeron pulchellus, Calystegia spithamaea, Symphyotrichum oolentangiense, Sisyrinchium campestre, etc., etc. This was the typical state of the groundlayer vegetation!

The WDNR had purchased the woodland several years prior for the purpose of the boat launch. There was access to the island by a narrow lane of old fill that had been put in for access to a small lakeside tavern (now long gone) in the early part of the previous century.

The assessment was specifically to delineate wetlands and flag the locations of forked aster (Eurybia furcata), a state-threatened species that had been found there during a prior assessment associated with the land purchase in 2012. I found and flagged several patches of forked aster scattered around the island. I emphasized to the WDNR property manager, who was present for the assessment, just how special the woodland was. He assured me that the impacts would be minimal, sticking largely to an existing mowed loop, but it was going to be a paved, American with Disabilities Act-compliant launch.

I contacted some local stakeholders and advised them of a public meeting (listening session or some such thing) about the launch, warning about potential impacts to something precious and irreplaceable, and I promptly got an upset phone call from the property manager (though I appreciate him not going straight over my head like the Milwaukee County Parks Natural Areas Coordinator did a few years later). In hindsight, I kind of wish he had called my boss. It might have freed me up to more strongly oppose what was about to happen.

This was taken in 2020 after the paving at the launch. You can look at the 2016 photo and see that we’ve lost one mature white oak. The other two are going to die, having had large portions of their root zones graded down and paved over. Much of this area was covered with the same sort of rich groundlayer shown above.
They paved a circle, but they still had to pave this turnaround, I guess, and they had to put the aquatic invasive species removal area down on top of the irrepleable woodland and not in an existing large gravel parking area just uphill of the access.
Large parking area at the top of the hill. Pave this FFS! Also, the runoff from this all follows the access downhill, carrying tons of sediment with it. Where does it end up?
It ends up in the wetland. Really WDNR? We deserve better. The visible flora are mostly Aronia melanocarpa, Ilex verticillata, and Osmundastrum cinnamomeum or those interested.

Aldo Leopold wrote (and this resides in my profressional email signature), “A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise.” What happened at Army Lake wasn’t just wrong, it was insane. Really, the forked aster was the only thing there with protected status that might have helped it, but that’s also insane, because communities support rare species; it’s not the other way around. …and the project led to take of some of the forked aster I had flagged. Was there any public notice of this incidental take or permit before the fact? No. Work began without a permit, and one was issued ex post facto. The WDNR is a resource conservation agency that operates in the public trust. Conservation all too often defeats itself.

Seeing this was a gut punch. It was a failure. This was a hill worth dying on. I’m happy to say that there are folks working to protect what is left and minimize the impacts. I also have learned a lot from this place and drawn inspiration from it. I was able to share it with a few people before the launch went in. Still, it’s difficult for me to look past what happened. It’s yet one more thing that my kids won’t see in full glory. Europeans came to the Midwest and stole this benevolent landscape for pasture, crops, mines, and development; when will we stop savagely destroying it?

Primula meadia is abundant in much of the woodland.
A riot of Vicia caroliniana and Pedicularis canadensis at the Army Lake Oak Woodland.
Krigia biflora, Comandra umbellata, and Vicia caroliniana.
Luzula multiflora with Aureolaria grandiflora in the background.

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Oak leaves must burn to release their ghosts and set the stage for renewal.

A fitting scene for this election day. Tomorrow will be welcome.

Any steward presiding over bur oak that does not welcome fire onto the landscape, or at least relentlessly try to do so, is a steward in name only.

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