Trying to Figure Out What We Did Right

When converting crop land to restored prairie, it’s always hard to predict what you’re going to get.  Numerous examples prove that even when you control as many variables as possible – including soil conditions and the rate, timing, and technique of planting – no two seedings turn out alike.  Sometimes, you can use hindsight to explain what happened (weather conditions, herbicide carryover, etc.) but most of the time it’s clear that we just don’t understand much of what’s happening out there.

I’ve been analyzing some data from one particular restored prairie lately, and trying to puzzle out what’s going on.  In this case, the results are good – which is nice.  It’d be nicer, of course, if I could explain WHY things worked so well and then replicate whatever happened…

The Dahms 2000 prairie restoration has turned into one of the most aesthetically pleasing prairies we manage along the Platte. It has tremendous diversity and abundance of wildflowers. Most importantly, its plant diversity is still increasing fairly rapidly after twelve field seasons.

The prairie in question was seeded with a mixture of about 200 plant species onto 69 acres of disked cropland that had been in corn the previous season.  The seed was planted sporadically between December 1999 and April 2000.  Wetlands were added to the site by excavating down close to groundwater and recreating the kind of swale/ridge topography that is typical of nearby Platte River meadows.  Those wetlands and sandy spoil piles (ridges) were seeded with appropriate seed as well. 

All of the seed was broadcast onto the site – some by fertilizer spreader and some by hand (I was experimenting) and no harrowing or packing of the soil was done.  Unfortunately, this was the last year BEFORE I started keeping good records of the amount of seed from each plant species I included in the mixture, so I only have a list of the species we harvested seed from that year.  What I know is that my seeding rate per acre was about 15 gallons of grass seed (mostly big warm-season natives) that was harvested by combine from nearby prairies, and about 1/2 gallon of hand-harvested forbs, grasses, and sedges.  That’s roughly 12 bulk pounds of grass seed and 1/2 pound of forb (wildflower) seed per acre.  I have no idea what germination rates were that year, but it was a pretty light seeding rate compared to what many others around the country use.  Today, our typical mix is a little lighter on grass and includes about twice the forbs.

To cut to the results, this prairie has turned into our most diverse and showy restoration we’ve ever done.  You’d never know we’d used such a light seeding rate of forbs by looking at the site now – its appearance is dominated by big showy wildflowers.  By every measure I use to look at the plant communities of our restored prairies, it comes out high.  I’ve found 178 plant species in the site so far, which is excellent.  The mean Floristic Quality (combination of species number and “conservatism values”) is high, and still climbing rapidly.  It averages twelve plant species per square meter, which is higher than most other restored or remnant prairies in the area.  (Yes, I know that seems like a very low number to you eastern tallgrass prairie folks, but it’s good for out here.  Don’t rain on my parade, ok?)  Twelve years after it was planted, tall warm-season grass species are still not very dominant.  The species found at the highest frequency is big bluestem, and it was only in about 80% of 1m2  plots stratified across the site last June.  In short, it’s a beautiful prairie.  And I don’t know why.

I know most of you are ITCHING to see the actual data tables and graphs, but because there are a few who aren’t, I’m including them as a PDF file, which you see by clicking here.  The PDF also includes a cumulative list of plant species found in the restored prairie.

Flower species such as black-eyed Susan (foreground) and bee balm (pink flowers in the background) are still dominating the plant community in this photo from 2009 (the 10th growing season of this seeding). The lasting abundance of those species is, I think, tied to the lack of dominance by major grass species.

It’s particularly impressive that this seeding turned out so well, because the odds seemed stacked against it early on.  It was seeded right at the beginning of a 7 year drought.  The first several years were dominated (as usual) by weedy species and a few colonizing native species such as Canada wild rye and common evening primrose, but in this prairie those species remained dominant for several more years than is typical.  Once other plant species started breaking through, there were few legumes present – and we don’t typically have problems establishing legumes in our prairies.  Those legumes are still more scarce than in other nearby sites, but they’re increasing over time.  Finally, in about its eighth season, the site stopped looking like a weed patch and matured into something that most people would recognize as a prairie.

As I’ve discussed in other blog posts, I’m still struggling to define success in our overall prairie restoration efforts, but at the scale of individual seedings, there are a couple things I look for.  First, I want to see a good diversity of plant species, and I want to see that diversity sustain itself over time.  Second, I don’t want to see invasive species increasing at the expense of that overall plant diversity, even as the prairie is exposed to disturbances such as drought, fire, and grazing.  So far, this restored prairie passes those tests with flying colors.  We’re moving toward implementing some measures of invertebrate use as well, but aren’t there yet.  Initial data and observations, however, show higher butterfly abundance and diversity in this site than in other nearby restored prairies – for whatever that’s worth.

The prairie has been managed with some periodic fire and grazing, which should be helping to suppress dominant grasses. However, this site has gotten much less of that kind of management than nearby restored prairies, and those other prairies have stronger populations of major grasses, so management can't explain the whole phenomenon. In this photo, cattle are grazing in the burned portion of this site - within a patch-burn grazing system. The grasses are primarily grazed short, helping to showcase the abundance of the forbs.

So why did this restoration turn out so well?  I really have no idea.  It caught a couple nice rains during its first spring, but the rest of the summer was awfully dry.  The overall seeding rate for forbs was considerably lower than we use now, but I don’t know how much seed we had of individual species.  I wish I understood why it has taken the big grasses so long to fill in, but I don’t.  I think the delayed grass dominance probably plays a role in encouraging the abundance and diversity of wildflowers at the site, but I don’t know how to replicate it.  The soils at the site are a little sandier than some of our other sites, but we’ve worked on sandier soils and had very quick grass establishment, so it seems unlikely that the sand is the key.

Besides its aesthetic appeal, the prairie is also a great seed harvest site because of its wildflower abundance. Nanette Whitten (left) and Mardell Jasnowski (right) are harvesting seeds in this photo.

The vast majority of our prairie restorations turn out pretty well, but this one is extraordinary, and I can’t explain it.  Was it something about our technique?  Something about the weather or soil conditions?  I know I should probably just be happy with the results, but I want to know WHY! 

Success is sure frustrating.

30 thoughts on “Trying to Figure Out What We Did Right

  1. Were any other restorations done in the same year from the same seed? (Can you rule out that the seed itself that was harvested and planted here was of higher ‘quality’ than usual?) Totally ‘out there’ question which I always find fun … do grasses conserve energy in drought years by setting less seed – forbs doing the opposite? Maybe forbs benefited more from the drought than the grasses?)

    • Good questions, Teresa. We did one other planting with the same seed mix – out by Kearney. Looks nothing like this one. In fact, it’s not really very good at all. Maybe it’ll get better over time too…? No, I can’t rule out seed quality, but I doubt that it’s the answer.

      I’m not sure I have a good answer to your second question. From what I’ve seen there are certainly species of both grasses and forbs that react to drought by going dormant and conserving energy. Others, especially short-lived species, can take advantage of that and increase in abundance. So yes, drought years certainly benefitted some species over others. I feel pretty confident that the wild rye was a winner during those drought years. And it would make sense that big bluestem and other grasses would have had a hard time during those dry summers of the drought. However, other restored prairies planted the year before and after turned out strong crops of those big grasses. Who knows?

  2. Wow, you ecologist types are a hard bunch to please… You cannot be satisfied by just succeeding (and taking the credit). You have to then ruin it by asking “Why?”

    Stephen Packard answers this question by saying, “Well, a butterfly flapped its wings in the Gulf of Mexico and …”

    I equate ecosystems to our immune system. Like the development of antigens in our immune system, overtime a whole host of interactions have been evolved which allow more conservative species to dominate and drives diversity in the system. Given the relatively huge number of soil microbes compared to all other species, it would make sense that these life forms are the main drivers of diversity.

    How do you replicate this success? Well, sometimes you get lucky and the magic formula is already present. All the other times a restorationist would be wise to do lots of tests. Seed various test plots minus some of the species. If one species dominates a test plot then you know the ecosystem does not have the “antigen” necessary to keep it from becoming virulent. Once you know which species will not dominate the site, only include those in species for seeding the remainder of that specific site.

    Why not just restore the microbes? Well they are a finicky bunch. Most won’t even grow in a lab.

    I also was wondering if snow depth had an impact. They have found that increased snow depth in arctic ecosystems causes more nutrients to be recycled during the summer months. Is it possible your ridges are helping to hold more snow? Is this protecting the soil from those Nebraska winters? Maybe some snow fencing would be worth putting in your restorations to see if this makes a difference.

    Also, don’t be feeling sorry for yourself because our prairies have more diversity. We count our prairies by the acre (or less) and you count yours by the section. It seems to me you are the lucky one.


    • Isn’t biology great, whether one’s primarily interested in square miles or just a human organ (or smaller)?
      I work on improving a three acre, six year old reconstructed prairie that I discovered four years ago when I moved back to my childhood home. I consider myself fortunate to have this to work on. I’m unfortunate because I, myself, have little useful prairie experience and there’s no one else to help me.
      Chris, your story reminds me how far prairie work has come in a few decades. It also maintains hope that such wonderfully brief 12-year good outcomes can happen.
      Especially because Chris may work on larger areas than we eastern tallgrass prairie folks, I surely agree with you, James, that he is “the lucky one.” Maybe in 12 years I too will be lucky after much effort and multiple attempts.
      I have no children, but your thought, James, brings to me another question: Are parents with one or more amazing children overly concerned why their kids are brilliant or beautiful or extraordinarily talented? Of course not. They are overwhelmingly thankful.

    • Thanks James. I agree that soil microbes likely play a large, and we don’t understand them much at all. Why they’d be different at this one site, I have no idea.

      I doubt if snow depth made too much difference here. We have wetlands and ridges on quite a few of our restorations, so this one’s not unique in that regard.

      And I’m not feeling sorry for myself because of our lower species density. I’m quite happy with the prairies we have around here. I just wanted to be sure that people weren’t trying to compare apples to oranges.

      • Chris, I have been contemplating my comments on snow depth. I do not know if snow depth is a driving factor, but I have definitely noticed aspect is very important. The aspects that seem to have the most diversity are Southern and Western. It would seem these aspects would have the least amount of snow since they are directed toward the prevailing winds. I always thought this diversity was driven by the fact that these aspects seem to be the driest. However, the increased exposure to cold winter temperatures could be a significant factor.

        Have you ever noticed how patches of vegetation seem to develop in restorations. You have a large dominating patch of Monarda here, Stiff Goldenrod there, and Rattlesnake Master in a different location. This occurs despite your best efforts to evenly distribute seed. Is anyone looking at changes in the dispersion of individual species instead of concentrating soley on the coefficient of conservatism and diversity? It seems to me that the mechanisms effecting dispersion are the drivers which create diversity.


        • It is interesting to think about, isn’t it? South and west facing slopes are driest during summer because they have the most sunshine, but I actually notice south-facing slopes getting more snow than other aspects because most of our snow storms are accompanied by north winds. So maybe they end up with more spring moisture but less summer?

          The patchy establishment in restorations is sure interesting too. Some, I’m sure is just random seed fall and establishment. Soil patterns – small and large scale – certainly play a role. Maybe also things like proximity to small mammal burrows (granivory)?? Putting the same seed mixture over a large site with lots of topographic and soil variation results in really cool heterogeneity tied to those physiographic features. I have only observational data on how species are expanding and moving (spatially) but they certainly do so.

    • I don’t think Chris will mind if I answer this, MrILTA. It’s Salvia azurea, a long and late bloomer native to the western 2/3 or so of the tallgrass prairie. Some planted this year is still blue in my backyard as I write. Not strictly native as far east as St. Louis, it long ago migrated eastward along the railroads, and also now is widely planted a good distance east of its native range of, say, 200 years ago. In a garden, I recommend some serious cutting back before Aug. 1, to make it branchier and less likely to flop over. Indeed, it puts on a good show in September around here, in some prairie plantings that get mowed in July, together with resprouted ironweed,a beautiful combination. Bumblebees and various butterlies love it.
      (Special deal for fellow ant enthusiast / native plant nut — I can send you some seeds from the ones in my back yard to try, if you like. Just remind me in a couple of weeks.)

      • Yep, what Trager said.

        Salvia’s a great species here. Easy to establish, and provides some different color to the landscape from an aesthetic standpoint. The Dept of Roads in Nebraska likes it for the same reasons. Fine with me!

  3. Chris,

    I tend to agree with your tentative conclusion that the delay in establishment of the big warm-season grasses allowed greater forb diversity to establish. Maybe the key is the early dominating species (you mentioned Canada wild rye) and their impact on preventing big grasses establishment? Canada wild rye is an interesting grass. It is suppose to give way quickly to the big warm-season grasses. But I have seen many cases where it comes in strong in areas and adjacent patches of big warm-season grasses seems unable to invade. Maybe your distribution of big warm-season grass seed was uneven? Some folks around here are planting very little big warm-season grasses in their mixes. I have seen mixes as low as 0.5 lbs/acre. I have always wondered if over time the big grasses will catch up?


    • David – Canada wild rye is certainly interesting. Lots of debate around here about whether or not it should be used in fairly high abundance as a cover crop of sorts. From what I’ve seen, it always gives way eventually to big warm-season grasses, but we haven’t seen a lot of people trying extra low seeding rates of those warm-seasons. Typical seeding rate of those grasses in high-diversity plantings is somewhere around 2-5lbs PLS/ac.

      I’m sure the distribution of W-S grass seed was patchy because much of it was hand-planted. I can see those patches today, if I look carefully. However, we’ve done other sites by hand and not seen the same delayed response…

      Who knows?? I’m still enjoying it.

    • Vincent – it’s a great point. I did not do a good job of tracking that info down, and you’re right that it could be important. My guess is that I wouldn’t have learned too much because the same farmer farmed several other fields we’ve restored, and they’ve all turned out differently! But – I do think herbicide carryover, potential impacts on soil structure and fauna, and other aspects of farming are likely to have pretty significant impacts on subsequent restorations. We just don’t know which aspects are the most important! I do think it was a field with relatively low yields, so I’d guess soil organic matter levels were fairly low – and that could certainly reduce vigor of grasses and favor forbs in my seeding.

      Thanks for the thoughtful comment.

  4. Chris, I am doing a few small prairie plantings in central Illinois. Most of the time I am starting with areas dominated by cool season grasses like smooth brome or fescue, spraying them down with glyphosate for a couple of seasons (to try to cut down on the weed seedbank), and then broadcast seeding them in December. It’s been recommended to me to keep newly-seeded plots mowed at a height of 4-8 inches for the entire first growing season in order to keep weeds like foxtail and ragweed from overtopping my new seedlings. This mowing regime makes me hesitant to try to seed more than a couple of acres at a time because I’m not sure I’ll have time to mow a large area that often. Do you find that first-year weed influx poses a threat to the development of your planted species?

    • Rich – it’s a great question. On our sites here, I’ve not found that mowing makes a difference. If anything, it might speed up grass establishment. But – the impacts on young seedings from weeds and mowing seem to vary from site to site. I don’t ever worry about species lik foxtail and annual sunflowers, but have seen a few instances where giant ragweed seems to shade things out in patches to the point where the plant community never progresses. However, others – especially in very productive soils – find that mowing does make a difference. My best advice is to test it yourself. I would follow the local advice to mow, but leave a few areas unmowed so you can see how things go without it. You might find that while it’s ugly for the first couple years, the results from not mowing look pretty good after 3-5 years. Or you might find that it’s a disaster. Either way, you’ll know how to proceed!

      I also think starting small (couple acres at a time) is a good idea regardless of the mowing issue, because you’ll likely learn some other tricks that will help you improve as you go. Plus, because every seeding turns out differently, you’ll end up with more diversity when you’re done than you would have by doing it all in one fell swoop. And – it’s likely that you’ll learn enough from your first couple attempts that you can increase the size of your seedings over time.

      Good luck – and have fun!

    • Chris, Good point about snowstorms having a North wind. Although the prevailing wind is Southwestern, you are correct that wind during snowstorms is usually out of the North. I do not believe moisture is the limiting factor in our area. We usually have plenty, especially in Spring. However, the protection from extreme Winter cold is unquestionably very important.

      I have also been contemplating the effect of “granivory.” I have been thinking more about ants than rodents. Maybe Mr. Trager could give us more information about the seed collecting habits of ants.

      We have noticed that certain species will dominate after the removal of invasive species. For example in woodlands, Eupatorium purpureum tends to dominates immediately after the removal of buckthorn. After time, this species’ numbers become significantly reduced. This population trend seems to be a boom that occurs when resources become available followed by a bust that I assume can only be attributed to an increase in pathogenic/parasitic organisms. After a number of years the population appears to stabilize at a more balanced level. In contrast, in restorations Andropogon gerardii usually dominates over time. Introduction of parasitic plants helps, but your region does not seem to have these. Various microbes, nematodes, and even ant cultivated root sucking aphids help prevent the dominance of species in remnant prairies. Unfortunately, these life forms expand their range very slowly. I often think soils must progress through a long development before the habitat even becomes suitable for these pathogenic/parasitic species.

      • Chris, I just noticed from your comment that you must have misinterpreted what I wrote. The word I used in the comment on November 15th was dispersion, not dispersal. Although these words sound similar, they are two very different concepts.


  5. Another though provoking essay with lots of good feedback, Chris — Thanks!

    Ants are neither very diverse nor abundant in early restorations, compared to in established plantings, and in any case the ant fauna of our humid grasslands doesn’t contain many granivores, and none of them are very abundant. Some ants do harvest elaiosome-bearing seeds, and the mound builders incorporate seeds along with other smalll vegetable fragments as building material in mounds (but also do a lot of pruning and weeding on the mounds), certainly with dispersion effects, but the species that do these things are are often not present early in the restoration process. I would think other seed-eating insects, scavenging invertebrates such as millipedes or even earthworms, decay, and descending hordes of blackbirds and sparrows probably do immensely more seed destruction in restorations than do ants.

    So we’re still left to wonder . . .

  6. Chris,
    I think the keystone species in many restorations are the early successional species-Canada wild rye, goldenrod sp., sunflower sp., Yellow coneflower, and Bergamots of the world. It does not take very many seeds of these species to dominate and to keep other species at bay, (weeds and/or warm season grasses). They dominate for a couple of years and then tend to shrink through the years of restoration giving way when the more conservative species are established/flowering.

    Goldenrods seem to have alleopathic effects. Yellow coneflower blooms abundantly for 3-4 years then almost disapears-I am not sure why, but it reappears in small doses when conditions are favorable for it. Bergamot and Canada wild rye seem to not tolerate competition. The collaboration of these species together seem to set a good base for conservative species to establish and in the end to get a full functioning prairie.

    • Bill, I agree with much of that. What’s interesting about this particular restoration, though, is that those species such as Monarda and stiff goldenrod (along with black-eyed Susan and yarrow) are still really abundant, even after 12 years. I assume they’ll taper off at some point, but it’s curious that they haven’t yet!

  7. As an amateur restorationist I can only comment on what I have observed on our farm. We seeded in 1993 with a grass heavy mixture and forb seed collected from prairie remnants on the farm. We are in the southeastern Red River Valley in MN and the dominant species is Big bluestem. Early on, Indiangrass was very prolific after the first burn in 1996, it was seeded with an equal amount of Big bluestem @ 3# per acre. Now, when we harvest for seed, depending on the parcel harvested, Indiangrass can comprise as little as 10% of the grass seed. I first started to see Small white lady’s slipper show up in the restored acres in year 13 or 14 (2005-2006), this was an exciting discovery and we now have many locations throughout the restored acres.

    The restored acres have really started to blur the line between the prairie remnants in the last several years with a vague but still identifiable border. The soil of the prairie remnants is softer under foot and of course the species diversity is far greater. The restored prairie has become very dynamic in the last few years (years 17, 18, 19) and a burn is not needed very often to maintain vigor. The duff layer from the past year disappears over the next year’s growing season so the microbes and other unpaid workers on and in the soil must be doing a good job. Even the unburned acres will produce a fair amount of harvestable seed the year following the burn.

    The prairie clovers, goldenrods and asters are the dominant forbs but many Closed gentian and Nodding ladies tresses have appeared in the last several years. Blazing star is found throughout and some later overseeded Fragrant false indigo has really taken off. Prairie cordgrass was not in the original mixture but has worked it’s way from native ravines into the restored acres where suitable at the rate of about 10′ per year.

  8. Chris,

    I planted 6 grasses originally, Big bluestem, Indiangrass, Little bluestem Switchgrass, Sideoats and Green Needlegrass. The green needlegrass disappeared entirely after about 4 years but yet is found in our prairie remnants on the farm.

    The number of forbs planted originally was about 20, the prairie clovers, blazing stars, goldenrods as the most available seed. I have really only added Fragrant false indigo along with Western sandcherry since the original planting. Leadplant has crept in from our remnants along with the species mentioned in my first post. Some species appearing on their own like Wild licorice and Canada tick trefoil are really dense in small patches showing an affinity for very specific soil conditions (sandy, light soil with some sub-irrigation).

    I really need to start adding species to the restored acres like Virginia mountain mint, Prairie onion and Prairie violet which occur in great numbers on our native sites. I have been managing with the Greater prairie chicken in mind but have also become very interested in the Regal fritillary butterfly so I will only burn 1/3 of the acreage in any given year. I would welcome any information you may have on the Regal and how to manage for them, it is somewhat rare in the northern prairies.


  9. Chris,
    You broadcast the seed without mechanical incorporation. Good seed to soil contact is required for germination. The south and west facing slopes have more freeze thaw action, so more cracking and opportunities to get the seed from the top of the groud to the bottom.
    Several years ago, our neighbor planted a CRP area we drive cattle across to a pasture we rent. For the first few years of the drought, it was a big sandbur patch. Then one year, the planted grasses germinated and the sandburrs practically disappeared. None of us has any idea why, but the seeded grasses had been dormant all that time.

    • Rex – Thanks for the comment.

      My impression with our sandy loam soils is that we get pretty good seed/soil contact through rains and snowmelt on the cropfield soils we plant into. I’m not sure, of course, but I don’t think the freeze/thaw cycles are that critical to us, especially because we really don’t want those seeds to be more than a tiny tiny bit covered by soil. Since we’re not trying to get the seeds down through plant litter, but are basically broadcasting them onto bare soil, I think incorporation isn’t necessary. In fact, I’ve been surprised not to have seen differences between establishment of sites where we broadcast into newly disked fields (which should increase seed/soil contact) vs. freshly harvested soybean fields (with no disking or other treatments). Interesting…

  10. Chris,

    I really enjoyed this post, and your beautiful wildflower photos. Regarding your comment about excavating down to groundwater in order to create wetlands, I am curious about the plant communities that developed in the areas where topsoil was removed (and how deep you excavated). Also, did you have good luck getting plants established on the ridges? In our Willamette Valley, OR prairies (where we have higher clay soils and lower organic matter), such practices often result in low plant diversity or stunted plants.


    • Hi Sarah,

      Glad you liked the post. In our sandy soils, excavation and seeding result in very nice plant communities. The wet sand of our excavated wetlands are very supportive of new wetland plant communities, though sedges come in slowly (but surely). The spoil piles (ridges) establish best when we bury the old topsoil at the bottom of the pile and seed into the bare sand at the top – fewer weeds, but the sand prairie plant species still establish well. We use seed mixtures of about 230 plant species (between wet, mesic, and sandy) so there’s usually something that establishes well everywhere. I’m happy to give you more details if you want.


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