Gneiss to Meet You

Gneiss to Meet You

Gneiss to Meet You

Exploring a Rare Prairie Growing Upon Some of the World’s Oldest Rock

Story and Photos by Addeline Theis

July 25, 2023

Pulling up at the edge of a gas station parking lot in the small town of Morton, Minnesota, I had to double check if this was the correct way to enter the prairie. A small foot path leading up through hipheight sumac bushes was visible from my car.  It was a sign that others before me have taken this way to view the historical outcroppings. Obviously, this was my first ever visit to Morton Outcrops Scientific Natural Area (SNA). Unknowingly, I scrambled up some boulders to find myself above the landscape, overlooking the amazing river valley. Below my hiking boots were dark slabs of granite that were covered in encroaching lichen. Finding a lichen-less portion of the rock, I noticed distinctive swirling of the pink and black bands. This was the 3.6-billion-year-old Morton Gneiss (pronounced “nice”) dry prairie that the site was preserved around.

This site is one of Minnesota’s largest and highest quality examples of Crystalline Bedrock Outcrop Prairie, defined as a dry, open, lichen-dominated plant communities on areas of exposed bedrock. Woody vegetation is sparse within this prairie type, and vascular plants are restricted to crevices, shallow soil deposits and rainwater pools. Shallow soils found on the margins of the bedrock exposures host plant species that are adapted to this drought-prone microhabitats. This prairie system is quite different from the wet prairie potholes that developed all around this river valley and the species found at this dry prairie showcase the difference. As a botanist, finding the native Brittle Prickly Pear Cactus (Opuntia fragilis) thriving out of the knobby exposure was exhilarating. The idea of such an arid plant flourishing in this site is one of the driving forces that led me to investigate the natural history of this site further.


For geologists, the glacial history of southwestern Minnesota tallgrass prairie region usually does not draw up much interest. The last glacial period left this area covered in thick glacial till, covering up any bedrock for one to investigate. For soil scientists, this thick glacial till was the original parent material for developing the thick rich Mollisols soils that the prairies are known for.   

What draws geologists into this area is the events that happened after the glaciers melted. After the Des Moines lobe of the Laurentide Ice sheet retreated from southern Minnesota and the global temperature began to rise, meltwater began to collect in large inland lakes throughout southern Canada and the northern Midwest. The largest of these lakes was ancient Lake Agassiz. Varying water levels led to the lake overflowing a moraine ice dam near present day Browns Valley, creating an outlet river. Called Glacial River Warren, this outlet river was a prehistoric river that drained Lake Agassiz between about 13,500 and 10,650 BP (Before Present) years ago. The strength and power of Glacier River Warren carved out the valley that is now known as the Minnesota River Valley.

This violent history impacted the landscape of southern Minnesota as well as affected how plant communities would development within the valley. The tremendous power of Glacial River Warren cut through layers of glacial till and clay-rich deposits of weathered bedrock all the way down to scour some of the oldest bedrock in North America. Some of the bedrock exposed on the valley floor is as old as 3.6 billion years old. It is called Morton Gneiss (pronounced “nice”), and it formed deep in the earth’s crust, where extreme heat and pressure changed, or metamorphosed, an earlier kind of rock. The beautiful and distinctive banding of colorful minerals within the Morton Gneiss makes it an attractive building stone, which is used around the world. There are just a few similar exposures of Morton Gneiss in Minnesota, all in the Morton Area.  
This place is also an amazing story of private landowner conservation, Carl Colwell was instrumental in the site’s preservation. After completing a career in the military, Carl returned home to Morton, Minnesota where he served as Renville County Historical Society director for six years. He purchased 10 acres as a private citizen in 2009.  

Today the land is protected as a Scientific Natural Area (SNA) managed by the Minnesota Department of Natural Resources. Colwell reflects:  

When I was a boy, the Dakota story I heard was that the rock was the keeper of all knowledge. It had seen everything since the beginning of time, and if someone would ask in the correct way, they would learn the answer. It was almost like a library. I, of course, didn’t believe that story at the time. Once I started escorting geologists, anthropologists, and “ists” of all sorts through the site, I started to hear the same story repeatedly. The rock has seen everything since the earth cooled. If we look carefully and study hard, we will learn the answer to our questions. 

Before returning to my vehicle, I took a few final moments on the ancient rocks, remembering that these rocks perhaps do have the answers to our questions. But only if we ask the right questions. I can only be thankful for the efforts of those that have contributed to the conservation and preservation of this site so that future generations can witness this library of knowledge within the Minnesota River Valley. 

If you’re interested in dry prairies, visit one of our sites, like Muralt Bluff Prairie. 

Book Review: The Gardener’s Guide to Prairie Plants

Book Review: The Gardener’s Guide to Prairie Plants

Book Review: The Gardener’s Guide to Prairie Plants

Written by Neil Diboll & Hillary Cox

Reviewed by Laurel Bennett

Neil Diboll, a well-known prairie ecologist associated with Prairie Nursery (also a member of the Prairie Sands chapter of TPE) and Hillary Cox, a botanist, horticulturist, and garden designer, have teamed up to write The Gardener’s Guide to Prairie Plants 


This 638-page book was originally intended as a field guide for identifying selected prairie species at all life stages. They certainly succeeded at that, providing extensive documentation on 145 prairie plants (18 grasses, 1 sedge and 133 forbs). But it is much more. Chapters range from “History and Ecology of the Prairie” to “The Prairie Food Web” but focus on establishing prairie gardens and ‘prairie meadows’, as the authors’ refer to a larger prairie planting, including propagating your own plants. Chapter 11 provides twelve different seed mixes for various combinations of soil types and prairie functions (butterflies, pollinators, deer resistant). Chapter 12 is stuffed with thirty more tables, covering many different parameters on prairie plants (color, height, bloom time, etc.) and some you might not even think to consider (root type, aggressiveness, groundcovers, specimen plants).  

The text is necessarily short on each topic but comprehensive in its coverage of the tallgrass biome. It is ideal for the beginner interested in planting and maintaining a prairie garden or ‘prairie meadow’ but even an experienced practitioner can pick up some good pointers.  

Surprisingly, the tables are not individually listed in the Table of Contents which would have been helpful. I also would have appreciated a few more references, so the reader could pursue topics in greater depth. 

There are a number of books and blogs on propagating prairie plants, on gardening with native plants, on establishing prairies and even a few on identification of seedling prairie plants. This book stands out for its breadth of coverage. 

You can find this book on Prairie Nursery’s website.

Find other interesting reads in our blog post: Our Winter Reading List

Change & Persistence Among Prairie Grasses

Change & Persistence Among Prairie Grasses

Change & Persistence Among Prairie Grasses

Story and Photos by Dan Carter

There are many misconceptions about prairies that cloud restoration, reconstruction, and management. Prominent among these is the tallgrass prairie “big four,” a concept that situates big bluestem (Andropogon gerardii), Indiangrass (Sorghastrum nutans), switchgrass (Panicum virgatum), and little bluestem (Schizachyrium scoparium) atop the dominant hierarchy of plants on tallgrass prairie. The “big four” has far-reaching influence on grassland management, scientific study, and seed mix design. It’s Tallgrass prairie after all!  

The “big four” are indeed co-dominant in many places where prairie vegetation occurs today. But, except for little bluestem, they were not historically the most dominant grasses on much of the prairie landscape, nor are they most dominant on many of the best remaining old-growth prairies.  

John Curtis (1959)1 described the composition of the least disturbed old-growth prairies in Wisconsin. Big bluestem was present on all studied mesic prairies, but porcupine grass (Hesperostipa spartea), Leiberg’s panic grass (Dichanthelium leibergii), and prairie dropseed (Sporobolus heterolepis) were the most frequent grasses. Frequencies from Curtis are the percentage of square meter quadrats a species occurs within for a given community type — basically how likely the species is to be at your feet if you are  walking in the prairie. porcupine grass was twice as frequent on mesic prairie as big bluestem! Big bluestem was the fifth most frequent grass on dry prairies behind little bluestem, side-oats grama (Bouteloua curtipendula), long-stalked panic-grass (Dichanthelium perlongum), and prairie dropseed; and third most frequent on dry-mesic prairie behind little bluestem and side oats grama. Only on wet-mesic prairie was big bluestem the most frequent among the grasses. Still, on wet-mesic prairie little bluestem’s frequency was about three quarters that of big bluestem. Prairie cordgrass (Spartina pectinata) and Canada blue-joint grass (Calamagrostis canadensis) were the species most often present (frequency data lacking) on wet prairie.  

In Iowa, The only grasses noted by Ada Hayden (1919)2 among the “principal” species of prairie remaining on the gently rolling uplands (mesic) immediately north of Ames, Iowa were porcupine grass and prairie dropseed. Later, Brotherson (1969)3, Kennedy (1969)4, and Glenn-Lewin (1976)5 studied composition on three old growth prairies in northern and western Iowa and found prairie dropseed, Leiberg’s panic grass, and porcupine grass to be the most common on uplands at the respective sites.  

In the Red River Valley of NW Minnesota, Dziadyk and Clambey (1980)6 described old growth prairie communities dominated by blue grama (Bouteloua gracilis) and porcupine grass on dry ground, prairie dropseed followed by little bluestem on gentle slopes, little bluestem followed by prairie dropseed on moderately well-drained level areas, and big bluestem and slim-stem reed-grass (Calamagrostis stricta) together on low prairie over poorly drained soils.  

Weaver’s and Clements’ (1938)7 concept of “true prairie,” which they extend to a region stretching from Illinois to Nebraska and northwest Minnesota to Oklahoma, is co-dominated by mid grasses—Porcupine grass, prairie dropseed, rough dropseed (Sporobolus compositus), little bluestem, side-oats grama, and needlegrass (Hesperostipa comata, in the west). Weaver worked extensively on prairies in the western part of the tallgrass prairie during the first half of the 20th century, including early study of fire effects at the Agricultural Experiment Station just north of Manhattan, Kansas. There, little bluestem and Junegrass (Koeleria macrantha) were initially the top two grasses (big bluestem was third). Composition shifted toward big bluestem with annual late spring burning but not late fall burning or earlier spring burning8,9. Indeed, late spring burning in the western and southwestern tallgrass prairie region to promote big bluestem for cattle pasture is part of why prairie composition changed there during the 20th century. Weaver and Clements observed these changes occurring and attributed them to the grazing and burning practices of the time, saying that the result was “that their [the mid grasses’] tallgrass competitors, notably Andropogon, gradually moved up the slopes and today appear to be essential members of the prairie relicts(page 458).  

Why did European land use sometimes drive compositional change towards the tall grasses like big bluestem?  

Late spring burning favors the growth form of long rhizomatous, warm-season grasses. Their growing points remain below the soil surface until very late spring or early summer, so growth of their active shoots can continue uninterrupted despite damage to aboveground foliage with late spring burns. The growing points of most bunchgrasses (e.g., porcupine grass, prairie dropseed, Leiberg’s panic grass, little bluestem, Junegrass, etc.) rise above the soil surface and become vulnerable to fire shortly after they initiate growth. If these are burned off, the bunchgrasses must activate reserve buds to replace the lost shoots. That alone puts them at a disadvantage, but their reserves of buds tend to be small compared to long-rhizomatous big bluestem and Indiangrass10, so their regenerative capacity is sooner exhausted (meristem-limited) in response to removal of active shoots. The cool-season bunchgrasses are hit especially hard by late spring burning because of their early growth, but even little bluestem, a warm-season species, can be harmed by later spring burns due its difference in growth form. Prairie dropseed, another warm-season grass, is harmed because it initiates growth nearly as early as the cool-season species despite its warm-season physiology. On most upland old growth prairie, late spring burning favors a subset of native grasses that was not historically so abundant.  

The effect of fire exclusion on composition can be similar to those of frequent late spring burning. Species with elongating rhizomes are better able to emerge through excessive accumulations of thatch. Hensel (1923)11 observed this 100 years ago in the Kansas Flint Hills. Little bluestem increased with annual early spring burning, but big bluestem replaced little bluestem atop the dominance hierarchy when fire was excluded. Weaver and Rowland (1952)12 also observed this in eastern Nebraska in the absence of burning, haying, or grazing: 

“Consequences of the effects of the mulch upon the environment were production of a nearly pure, but somewhat thinner than normal, stand of Andropogon [big bluestem]. The understory of upland prairie had all but disappeared. The usual mid grasses of upland were few or none. Only a few taller forbs remained.”—Page 19 

Burning in the presence of excessive litter accumulation, which often occurs on prairies that are occasionally burned (as opposed to frequentyly)kill or weaken little bluestem13 and other bunchgrasses (e.g., needlelegrass)14. Their buds are at or just above the soil surface and vulnerable to increased fire duration when excessive litter has built up. This is not the case for the deeply buried buds along the rhizomes of big bluestem or Indiangrass. Interestingly, excessive litter may interact with fire to affect prairie bunchgrasses and certain invertebrates (skippers: Hesperia ottoe and H. Dakotae)15 in similar ways, with responses contingent on the amount of litter accumulation!  

Native bunchgrasses decrease for many of the same reasons in response to confined grazing. Porcupine grass is very palatable and emerges before most other prairie grasses, so it disappears quickly upon pasturage16. The long-rhizomatous prairie grasses also decrease in response to grazing16, but they persist and recover relatively well during rest periods because they have greater reserves of belowground buds available for recovery and their elongating rhizomes help them colonize openings where vegetation has been thinned by disturbance. The position of buds on these long-rhizomatous grasses an inch or two beneath the soil surface also protects their regenerative capacity from mechanical disturbance 10,17. Weaver recognized the importance of rhizomatous habit for recovery from disturbance, but not bud depth or number. Nonetheless, where grazing was too intense and prolonged, most prairie grasses were replaced by long-rhizomatous, cool-season species like Kentucky bluegrass (Poa pratensis), except on the driest sites1,2,16. 

The work of Weaver, Curtis, Hayden, and others adds important context to our interpretation of more contemporary studies of prairie. They help us discern between research and management outcomes from altered grasslands that no longer retain old growth composition, and prairies that still do. Porcupine grass, little bluestem, prairie dropseed, side-oats grama, and/or Leiberg’s panic grass are usually among the prominent grass species on the best remaining old growth, upland prairies. All of those species differ from big bluestem in their ecologies in ways that have implications for management. Except side-oats grama, many of those differences stem from growth form, cool-season physiology, or both. Earlier work on composition also highlights the amazing persistence of well-stewarded and less historically exploited old-growth prairies in the face of unprecedented change. Upland old-growth prairies that retain much of their composition have typically experienced: 

  • fewer periods of excessive litter accumulation. 
  • fewer late spring burns and more burns between fall and early spring—the more frequent the better9,18,19. True prairie composition was and is an expression of dormant season fire.  
  • minimal fenced grazing. Free-roaming deer, elk, bison, and their predators/hunters are separate issues.  
  • less fragmentation19, but consider that small, less exploited prairies that are well-stewarded retain more of their historical botanical composition than landscape grasslands in the western tallgrass region. Little prairies are more vulnerable to neglect, which argues for their protection and care.  

While the confluence of these conditions is tragically rare, the persistence of what remains is reason to keep hope. True prairie in the Midwest has been home to members of east-west and north-south expanding and contracting flora, fauna, and cultures for millennia. Even an island of old-growth prairie carries with it immeasurable ecological memory. We can kindle that and facilitate its recovery through stewardship and by building connections among prairie places and prairie people…especially if we can get our hands on more porcupine grass and Leiberg’s panic-grass! 


1 Curtis, J. 1959. The vegetation of Wisconsin University of Wisconsin Press. Madison, WI. 

2 Hayden, A. 1919. Notes on the floristic features of a prairie province in central Iowa. Proceedings of the Iowa Academy of Science 25: 369-389. 

3 Brotherson, J. 1969. Species composition, distribution, and phytosociology of Kalsow Prairie, a mesic tall-grass prairie in Iowa. Dissertation, Iowa State University.  

4 Kennedy, R. 1969. An analysis of tall-grass prairie vegetation relative to slope position, Sheeder Prairie. M.S. Thesis, Iowa State University.  

5 Glenn-Lewin, D. 1976. The vegetation of Stinson Prairie, Kossuth County, Iowa. Proceedings of the Iowa Academy of Science 83: 88-93. 

6 Dziadyk, B. and G. Clambey. 1980. Floristic composition of western Minnesota tallgrass prairie. Proceedings of the Seventh North American Prairie Conference: 45-54. 

7 Weaver, J., and F. Clements. 1938. Plant ecology. McGraw-Hill Book Company, Inc. New York and London. 

8 Weaver, J., and A. Aldous. 1935. Role of fire in pasture management. Ecology 16:651–654. 

9 Towne, G., and C. Owensby. 1984. Long-term effects of annual burning at different dates in ungrazed Kansas tallgrass prairie. Journal of Range Management 37: 392-397. 

10 10 Ott, J., Klimešová, J., and D. Hartnett. 2019, The ecology and significance of below-ground bud banks in plants. Annals of Botany 123: 1099-1118. 

11 Hensel, R. 1923. Recent studies of the effect of burning on grassland vegetation. Ecology 4: 183-188. 

12 Weaver, J. and N. Rowland. Effects of excessive natural mulch on development, yield, and structure of native grassland. Botanical Gazette 114: 1-19. 

13 Gagnon, P., K. Harms, K., Platt, W., Passmore, H., and J. Myers. 2012. Small-scale variation in fuel loads differently affects two co-dominant bunchgrasses in a species-rich pine savanna. PLoS ONE 7: e29674. 

14 Haile, K. 2011. Fuel load and heat effects on northern mixed prairie and four prominent rangeland graminoids. Thesis, Montana State University-Bozeman. 

15 Dana R. 1991. Conservation management of the prairie skippers Hesperia dacotae and Hesperia ottoe. Minnesota Agricultural Experiment Station Bulletin 594, University of Minnesota. 

16 Weaver, J. 1954. North American prairie. Johnsen Publishing Company. Lincoln, NE. 

17 Klimešová J, and L. Klimeš. 2007. Bud banks and their role in vegetative regeneration – a literature review and proposal for simple classification and assessment. Perspectives in Plant Ecology, Evolution and Systematics 8: 115–129. 

18 Bowles, M. and M. Jones. 2013 Repeated burning of eastern tallgrass prairie increases richness and diversity, stabilizing late successional vegetation. Ecological Applications 23: 464-478  

19 Alstad, A., Damschen, E., Givnish, T., Harrington, J., Leach, M. and D. Rogers. The pace of plant community change is accelerating in remnant prairies. Science Advances. 2: e1500975  

Read more about Dan Carter’s work through our blog post: 2020 Landowner Services Update

Public Notice: We’re Applying to Renew Our Land Trust Accreditation

Public Notice: We’re Applying to Renew Our Land Trust Accreditation

The land trust accreditation program recognizes land conservation organizations that meet national quality standards for protecting important natural places and working lands forever. The Prairie Enthusiasts is pleased to announce it is applying for renewal of accreditation. A public comment period is now open.

The Land Trust Accreditation Commission, an independent program of the Land Trust Alliance, conducts an extensive review of each applicant’s policies and programs.

The Commission invites public input and accepts signed, written comments on pending applications. Comments must relate to how The Prairie Enthusiasts complies with national quality standards. These standards address the ethical and technical operation of a land trust. For the full list of standards see

To learn more about the accreditation program and to submit a comment, visit, or email your comment to Comments may also be mailed to the Land Trust Accreditation Commission, Attn: Public Comments, 36 Phila Street, Suite 2, Saratoga Springs, NY 12866.

Comments on The Prairie Enthusiasts application will be most useful by February 10th.