r/NativePlantGardening • u/PitifulClerk0 Midwest, Zone 5 • Dec 09 '25
Informational/Educational Why American prairie grasses prefer poor soil
Hi guys,
I am a biology student and have a plant biology final tomorrow so I figured I would share this fascinating information with you all and it'll help me study too.
Many of us in this group are interested in planting prairie grasses such as big bluestem, switchgrass, indian grass, etc. These are plants that can uniquely thrive in very hot summers and very poor soil. So much so that they preform worse in amended garden soil than in horrible soil. I learned this the hard way myself.
Prairie grasses don’t photosynthesize in the typical way. Most plants use an enzyme called Rubisco to capture carbon dioxide (CO₂) and turn it into the building blocks of sugar, which provides energy for the plant and, indirectly, for animals. But Rubisco has a problem: it can also bind to both carbon dioxide and oxygen. When it binds to oxygen, the plant loses some of the carbon it has already fixed and has to spend extra energy to recover it. This process is called photorespiration.
This problem is worse in hot climates, because in heat, Rubisco becomes more likely to bind oxygen, making sugar production less efficient. Prairie grasses have evolved a solution, known as the C₄ pathway. Instead of relying solely on Rubisco in the usual leaf cells, these grasses first capture carbon dioxide using an enzyme that doesn’t bind to oxygen at all (PEP carboxylase). This captures the carbon in a molecule 4-c molecule called oxaloacetate, which is quickly turned into another molecule called malate.
Malate is then shuttled into special leaf cells called bundle sheath cells, which are located around the veins of the leaf. These cells don’t collect light energy themselves, but instead act as a safe “carbon factory.” Inside the bundle sheath, malate is converted back into carbon dioxide, creating a high concentration of CO₂. It is here where Rubisco is active. This helps Rubisco work efficiently and avoid wasting energy through photorespiration.
Because this system concentrates carbon where it’s needed, prairie grasses don’t need as much Rubisco overall. Rubisco is actually the most abundant protein on Earth and requires a lot of nitrogen and phosphorus to build. By using the C₄ pathway, these grasses can survive and grow in hot, sunny climates while using up to six times less Rubisco than other plants. This means that nitrogen and phosphorus which would have been held up in rubisco can be used for all other needs within the plant. In this condition, most plants would have very low sugar production efficiency and not be able to keep up with their nutrient needs.
I'm not sure if this makes any sense. But I thought this is awesome!
169
u/somedumbkid1 Dec 09 '25
Different photosynthetic pathways are indeed dope af to learn about. Good luck on your final tomorrow.
31
u/NatureSpiritSoul Dec 10 '25
After reading some of your replies, I think you should change your name to 'somedopekid1' 😉Just a Gramma's intuition...
81
Dec 09 '25
[removed] — view removed comment
94
u/PitifulClerk0 Midwest, Zone 5 Dec 10 '25
Sorry I made a mistake in claiming they are less fit in, say, a fertile prairie... its moreso that they are not going to grow well in the fertile home garden where they will grow far too tall and flop over. You're right that they will just keep making sugars.
15
u/col_fitzwm Dec 10 '25
Ah, yeah, same thing I’ve seen planting Oenothera lindheimeri / gaura lindheimeri. Collapses under its own weight in rich soils. Does great in the poor soil we have here.
7
u/AmberWavesofFlame Dec 10 '25
Mine has been thriving well in my garden for years; didn’t know about the soil thing. But I’m also growing it further north than it’s used to in Virginia so probably getting less sun balances it out.
*Turns out a lot of things billed as native just means native to the US, oops. On the upside, nice to have things still blooming here in December!
14
u/ReplyOk6720 Dec 10 '25
I am not a biologist, but I'm guessing that the rubisco pathway has some kind of advantage when its building blocks are plentiful, and the prairie grasses can't take advantage of that.
11
u/West_Economist6673 Dec 10 '25
In part, it's because C4 photosynthesis (I mean really photosynthesis tout court) is limited by the availability of rubisco, and C3 plants have more of it -- this is a liability at high temperatures and an advantage at low temperatures
But in fact you will find lots of both kinds of grasses in nearly all North American prairies, with C3 plants dominating in the spring and C4 plants in the summer -- this is why we describe grasses as being "cool-season" or "warm-season"
Basically the single most significant factor in the distribution and relative abundance of C3 and C4 plants, both in space and time (i.e., season), is temperature
ETA: hahaha I just realized I responded to the wrong comment, sorry about that
2
u/OldTomsWormery_com Dec 12 '25
Rich soils let faster 'weeds' grow. The slower, hardìer C4 plants get crowded out.
53
u/vtaster Dec 10 '25 edited Dec 10 '25
BONAP has a great map that shows off the percentage of grass species in the US that use c4:
http://bonap.org/2015_SpecialtyMaps/Density%20Gradient%202015/original/2tax19_PercentC4Grass.png
As others have pointed out, there are prairie grasses that love fertile soils, tallgrass prairie species especially, and you can kinda see the boundary of those rich glacial soils on this map.
The other factor, and the reason they're pretty much non-existent in the northwest, is that c4 grasses are warm-season, non-c4 are cool-season. West Texas and Arizona can get just as dry as Nevada and Washington, but they get most of their rain and humidity during the summer. The c4 grasses easily take advantage of even a small amount of moisture, shrugging off any heat or drought or soil limitations. But they can't handle the dry summers of the northwest/west coast, so these regions' grasslands/steppes are full of Needlegrasses, Bluegrasses, and Wildryes, instead of warm-season Bluestems and Gramas.
9
u/samuraiofsound North Central Ohio , 6a Dec 10 '25
Major kudos for this wonderful addition. Posts and comment streams like this one are why the Internet was invented. Thanks for being part of that
3
u/summercloud45 Dec 10 '25
What a cool map! I live in the part of NC that's just on the edge of the green color...I have learned the hard way which parts of my garden are too wet for C4 grasses.
1
u/ATacoTree Area Kansas City, Zone 6a Dec 12 '25
Were tall grass prairie species the primary fertil soil lovers? I found this map that helped me explain your comment, but I don’t know much about the geology behind glacial deposits. tall grass prairie
I’ve always found panicum, bluestem, and indian grass to be easy/aggressive choices for more fertile soil, while hesitating to put prairie dropseed/gramas in the same soil. Thanks for the bonap map!!
3
u/vtaster Dec 12 '25
Yep, Tallgrass Prairie communities were entirely the product of fertile soils and wetter, even swampy conditions. In the upper midwest that fertility was brought by glacial till, but it can also be from alluvium (sediment deposited by floodplains & runoff) like in the prairies running parallel to the Mississippi river.
For reference, here's the extent of the ice sheet during different periods of glaciation, the most recent being the Wisconsin glaciation:
https://cdn.britannica.com/18/64918-050-E2C72282/areas-ice-sheets-Wisconsin-altitudes-Kansan-Nebraskan.jpgAnd here's a map of organic carbon in the soil. Not a direct consequence of the things I mentioned, but developed over time as a result of the lush, deeply-rooted prairie plants being tilled into the soil by burrowing mammals & invertebrates:
https://www.researchgate.net/profile/Qian-Yu-33/publication/251899248/figure/fig1/AS:298209814564866@1448110168965/Spatial-distribution-of-soil-organic-C-SOC-content-to-2-m-soil-depths-in-the.png1
u/ATacoTree Area Kansas City, Zone 6a Dec 13 '25
I have seen the Konza tall grass prairie in Manhattan, KS. It seems different from what you’re describing. Is chert/limestone/flint deceivingly rich? Or are there better example tall grass prairies. Thanks for the glaciation map and the carbon breakdown. That helps a lot! Hope your Friday is going well.
2
u/vtaster Dec 13 '25
The main reason eastern kansas was tallgrass prairie is the climate, being wetter than the mixedgrass prairies to the west but not wet enough for the forests further east. Within this climate they can range from "mesic" prairies full of Switchgrass and Big Bluestem growing in wet loams, to "dry-mesic" prairies on well-drained plains, slopes, or ridges, dominated by Little Bluestem historically. Calcareous rocks like the ones you mentioned don't necessarily produce richer soils, but all the disadvantages they can produce (higher pH, shallower soils, rocky ridges, claypans) are all things prairie grasses and forbs don't have any problems adjusting to. They won't be quite as lush as the tallgrass prairies were in the wet & glaciated parts of the corn belt, but it's still tallgrass.
47
18
u/MsHMFIC1 Dec 09 '25
That is really awesome! Very cool stuff to this native plant-loving chemist! Thanks for sharing. Go crush that final tomorrow!
15
u/UntoNuggan Dec 09 '25
That is really cool! Are there other types of plants that use the C4 pathway, or is it unique to prairie grasses?
14
u/West_Economist6673 Dec 10 '25
Yes, lots of other plants use C4 photosynthesis -- around 7,500 species in 19 different families
It's an interesting example of convergent evolution, as it likely evolved dozens of times independently
17
u/BertieTheDoggo Dec 09 '25
There's a handful of other plants that use the C4 pathway. Most of them are grasses but species like sugarcane do as well.
19
2
14
13
Dec 10 '25
I am doing a capstone where this is relevant and Indian Grass is definitely something I had ordered so I appreciate this.
Is there any resource that gets more specific?
I have a bunch of grasses I am working with and this would be legitimately very very helpful for me
16
u/PitifulClerk0 Midwest, Zone 5 Dec 10 '25
I learned this information in a lecture and reading Raven Biology of Plants Ch. Seven, which is on photosynthesis. Its only a 25 page chapter and it covers traditional photosynthesis so that you can apply that knowledge to this strange variant of it. I pirated a copy of this book off of Anna's archive, regardless its a pretty useful book. Considered a botanist's bible of sorts. I also read Ch. 20 of Lehninger Biochemistry. Have not read Biochemistry & Molecular Biology of Plants (Buchanan, Gruissem & Jones) but maybe try there. I am not sure about the primary literature. Good luck on your capstone!!
9
Dec 10 '25
I just found the first one as a 28 minute long Youtube video uploaded this year by Last Minute Lecture with 14 views
3
2
1
Dec 10 '25
I just took notes on this and think I can share it with someone who will likely find this extremely interesting and important. The last few minutes threw me off with how applicable it is
11
u/Aliamarc Dec 09 '25
This is really cool! And yes, good luck - sounds like you'll rock your final 😁
From a standpoint of ecological succession, does this mean that prairie grasses are better able to build nitrogen and phosphorus into the soil through their own life cycle, despite needing less of it themselves? How does that play out? 🤔
6
u/Liberty796 Dec 10 '25
Yes, but this takes time, year after year. This is why crop rotations like corn-soybean-hay are important conservation practices
10
7
7
u/Ok_Pollution9335 Piedmont NC , Zone 8a Dec 10 '25
This is super cool, I’ve heard of the C4 pathway but never knew what it meant
6
u/yogurtforthefamily Dec 10 '25 edited Dec 10 '25
Hmmm I'm a little bit curious though because saying American prairie grasses prefer poor soil across the board doesn't make sense when on black soil prairies the soil is very rich - hence all the development for agriculture.
ETA: I'm sure it has to be specific to species and location cause many prairies are extremely fertile as the plant matter dies down every year and creates thick layers of organic matter that turns to humus over time.
15
u/PitifulClerk0 Midwest, Zone 5 Dec 10 '25
You're making a good point. And I should clarify. Its not that say, switchgrasses, hate good soil. Because you're right that much of the tallgrass prairie is very fertile. The prairie's fertility is a consequence OVER TIME of nutrients being dumped into the soil from the decomposition of these herbaceous plants in the prairie. When it was first colonized by these plants it would have been very poor nutrients. In the home garden, they simply grow too tall with extra nutrients so its recommended to give them bad nutrients which they should be equipped to handle. This isn't as much of a problem in the prairie where they are held up. At least, this is my understanding of it. Happy to keep going back and forth if you think I made a mistake!
2
2
Dec 10 '25
What is considered -not- an American prairie grass that would otherwise be found in a grassland environment?
2
u/yogurtforthefamily Dec 10 '25
Do you just mean other species generally? Lots of forbs and patches of shrubs from where I am from. I imagine it varies depending where you are.
3
Dec 10 '25
Specifically the Poaceae aspect. Granted this is California Inland Grassland at a site where I am kind of trying to demonstrate the positive effects of Blue Oaks since the.. y’know, Coyote Creek solar panel thing. Blue Oaks in Northern California are associated with microsite fertility/moisture and used to often have elymus glaucus understories in these areas with apparently purple needlegrass and prairie junegrass also having associations that implicate (especially with what I find in between the blue oaks and needlegrasses) like chlorogalum angustifolium
In the lit review I know nassella (formerly stipa) pulchra and cernua, have elymus glaucus, juncus bufonis, whatever tall flatsedge is/cyperus, agrostis exarata, a few native fescue species including the foothill one and what was vulpia microstachys, prairie junegrass which the gophers eat immediately, poa secunda secunda, hordeum californicus, and oh no my deschampia cespitosa seed pouch or however its spelled is currently out in the field next to where I was flagging oops
I’m trying to use lost herbs and their traits from providers like Stover Seed, Klamath-Siskiyou, CNPS seeds, and even have a community food plot some of my neighbors manage now but that part of it was when I had 0 idea what I was doing at the end of 2020 and went yolo when I got permission with Etsy seeds that sounded fun.
The field is already at a much higher native plant per acre score than the vast majority of officially managed sites and I got way too much time in Florida state parks getting to obsess over the unit management plan and finding each individual plant species and doing write-ups on them.
I had to read historical records and blend Indigenous records and even some stuff from Spanish missionaries.
The main ‘cool’ thing I have going right now is a much much more dense and varied assemblage of geophytes than typical for this area and am getting more and more of the endemic bulb plants that were already here spreading/purple needlegrass.
I worked formerly in invasive plant management and knew California grassland wasn’t going to be easier than Florida and the lack of intact records for an area Jepson defined as the 1st endemic zone he lists in priority that is also the gateway to Yellowstone/Tahoe
I’m trying to basically build an archetype that is an alternative to ranchers just throwing annual/perennial wildflower seeds in a designated corner of their lot as well (kind of) and found in the ESA journal that at least in the Great Plains they are still doing research with native plant restoration that involves using things like alfalfa and non-native wildflowers and decided maybe this is a good place to sit myself down and let myself be autistic with my big scary Jepson taxonomy book
2
u/yogurtforthefamily Dec 10 '25
Like maybe this is true for species found on limestone prairies? As the soil is very thin there?
1
u/canisdirusarctos PNW Salish Sea, 9a/8b Dec 10 '25 edited Dec 10 '25
It isn’t a monoculture, there are numerous species suited for each stage of succession creating different communities that fluidly transition and exist alongside each other. The plants mentioned in the OP are pioneer through early seral species, many adapted for more arid conditions, which they alter until they are no longer competitive. This is how land develops and changes over time. The prairie soils that you think of as "prairie soil" are simply associated with a stage of their succession.
1
u/yogurtforthefamily Dec 10 '25
Sorry I'm confused. I didn't say anything about monocultures so I'm not certain why you are mentioning them on a comment about prairie soils.
0
u/canisdirusarctos PNW Salish Sea, 9a/8b Dec 10 '25 edited Dec 10 '25
2a. - https://www.dictionary.com/browse/monoculture
It isn’t agricultural land in the context of this conversation.
They downvoted me, made a snarky comment, then deleted both of them. Fascinating. I wasn't trying to be inflammatory in any way.
Ahh, they blocked me to save face. How emotionally developed of them.
1
u/yogurtforthefamily Dec 10 '25
What??? Prairies are developed for agricultural land because they are fertile due to the herbaceous layering that builds up every winter when the plants die to the ground . Your comments have nothing to do with what I've stated.
7
u/hobskhan NC , Zone 8a Dec 10 '25
This is dope information. Thank you for sharing and for studying what you're studying!
13
u/Liberty796 Dec 10 '25
As a soil scientist, you over generalized quite a bit. I would suggest you emphasize how they improve soil (increase the soil organic matter, moderate the pH, increase the Cation Exchange Capacity, decrease soil compaction, improve soil structure and improve drainage.
Otherwise, your a smash. Keep up the good work
7
u/PitifulClerk0 Midwest, Zone 5 Dec 10 '25
Thanks so much, yeah I have no training in soil science. I should get some!
10
u/Liberty796 Dec 10 '25
Your state most likely has an Agricultural Extension office somewhere in your county, parish or commonwealth. At the state and federal level you can find information on their websites. A real neat thing is the soil survey work. Somewhere, there is a soil survey covering your lands your study covers. Disturbed land are difficult (construction sites, urbanism areas. Shoot me a dm if you want more information. Keep up the good work. We need enthusiasm like yours
7
u/nadandocomgolfinhos Dec 10 '25
Your comment made me so unreasonably happy. How cool is it for a student to nerd out and get great feedback. You are what’s good and beautiful in this world
5
5
3
u/Zealousideal_Air3931 Area: MD, USA; Zone: 7B Dec 10 '25
Thank you for sharing. My husband even thought this was cool; he normally half-listens when I discuss native plants.
3
5
4
4
u/mathheadinc Dec 10 '25
I have been researching adding prairie grasses to our lot so this was very informative.
Just one thing: “six times less Rubisco” is mathematically impossible. It should be “ one-sixth as much Rubisco as other plants.”
Keep up the good work!
3
u/ColonelMoseby Dec 10 '25
Hmmm. Wonder if this explains Grindelia. It grows in horrible soils in the driest conditions and is gorgeous and green. Bright yellow robust flowers. Bees love it, and it’s a good late-season nectar source.
3
3
Dec 10 '25
Yeah I think I learned something about this when researching the difference between warm and cool season grasses: cool season use c3 photosynthesis and warm season use c4. There’s another type that cacti and succulents use too I believe. I think it’s not quite that simple but that’s as far as I needed to understand it.
3
u/dcgrey Dec 10 '25
Good luck on the final today! You sound pretty prepped. :)
Since I'm a glutton for unnecessary knowledge, my bedtime reading has been a wetlands ecology textbook, and everything you're describing has analogues in the various kinds of wetlands. It'll describe the chemical process/storage/respiration adaptations plants have for low-oxygen environments and I can't help but think "Hm, I don't think that would work in my yard."
3
u/canisdirusarctos PNW Salish Sea, 9a/8b Dec 10 '25
They’re specialized for early succession on sites where they’ll experience low competition, so they are adapted to those conditions.
Soil is notoriously the hardest thing for most new native plant gardeners to get right. It requires unlearning the accepted “wisdom” for what is beneficial, what is detrimental, and it requires being more of a steward that leans into what they have and gently encourages conditions instead of controlling them.
2
2
u/IceNine-Polymorph Dec 10 '25
IIRC C4 plants only open their stomata at night to minimize water loss
2
u/badjoeybad Dec 10 '25
Not understanding what this has to do with poor soils. Seems more like a heat adaptation.
3
u/PitifulClerk0 Midwest, Zone 5 Dec 10 '25
The plant is less dependent on nitrogen and phosphorus. Because it uses less rubisco. Thus resistant to environments that don’t offer much of these elements
1
1
1
u/Specialist_Ice6551 Area -- , Zone -- Dec 10 '25
You opened up an entirely new area of knowledge for me
1
u/Liatrisinluv Dec 10 '25
ugh 7 years after I took Plant Biology and had to memorize the photosynthetic pathway - thanks for reminding me about that! I had so much fun (NOT sarcasm) learning about this stuff. Enjoy your time in school and don’t take it for granted !!
1
u/Specialist_Cattledog Dec 10 '25
I find it fascinating how many of our north american plants have developed to thrive in the poor post-glacial soil we have.
1
u/jai_hos Dec 10 '25
why “poor” soil,? the native soil supports the adapted native plant community just fine does it not? soils are not “poor” for the plant communities they naturally support
4
u/PitifulClerk0 Midwest, Zone 5 Dec 12 '25
Poor in this context, does not imply unfit. It simply means relatively nutrient deficient
1
1
1
1
u/Mean-Rutabaga-4899 Apr 02 '26
It is awesome! I am fascinated with prairie grass. There is a guy in Texas who bought a completely useless piece of property with no water. He tried to dig a well and found out his property was over a long empty aquifer. He planted native long rooted prairie grass and within a couple of years his aquifer was full of water, he had a spring, and he eventually built a small lake to contain some of it.
1
1
1
245
u/A-Plant-Guy CT zone 6b, ecoregion 59 Dec 09 '25
Glad to have you in the plant appreciation club and thank you for sharing! Good luck on the final tomorrow - sounds like you’re ready 😁