What Are Spring Ephemerals?

In early spring, the understory of this deciduous woodland is bright with the flowers of false rue anemone (Enemion biternatum) and other spring ephemerals.

Spring ephemerals are herbaceous (non-woody) plants that emerge, flower, set seed and die back in spring. Many are woodland plants that take advantage of the brighter sunlight and more abundant moisture early in the season, before trees are fully leafed out.

These plants are an important source of nectar and pollen for insects that also emerge in early spring. The insects, in turn, are important pollinators for these plants. Ephemerals depend on them to fertilize their flowers so they can develop seeds. 

Because spring can be fickle, though, some ephemerals can also self-pollinate. If it's too cold for insects to fly, for example, several species can fertilize themselves. The resulting seeds carry the same genes as their parent, so the plants that grow from them are clones of that parent.

Vegetative reproduction also helps the plants spread. The false rue anemone pictured above, for example, produces not only seeds but also tuberous roots that can grow new plants. The large colony in the photograph is largely created in this way.

Most if not all spring ephemerals are perennials. After the plants flower and release seeds, the leaves of true ephemerals die back to bulbs, rhizomes, or other underground parts that store energy for next spring's growth. Some early-flowering plants keep their leaves for much of the growing season. Although these plants aren't true ephemerals, they are often included in that group.

Two Common Ephemerals

Dutchman's Breeches (Dicentra cucullaria)

Dutchman's breeches flower in April or May in the understory of deciduous forests. True to its name, its flowers resemble breeches (or britches) hanging upside down on a clothesline. 

Left to right: Dutchman's breeches flowering in early April; seed capsules ripening in mid-May; leaves gone by late May, leaving only light red tuber-like structures that store energy for next season's growth. 

The flowers are pollinated primarily by bumblebees and honey bees (1), but they can self-pollinate if the bees are absent. Seeds produced by self-fertilization may not be viable, however, and some consider the plants to be obligate out-crossers, meaning they form viable seeds only by out-crossing (2). After flowering, the plants develop elongated capsules containing dark, roundish seeds that are dropped from the capsules and distributed by ants (3). (See also Antsy Plants, a post about seed dispersal by ants.)

After flowering and seed formation, the leaves of Dutchman's breeches quickly decline. By late spring  only small, reddish bulbs or tubers remain. These storage organs are dormant until fall, when they develop leaf primordia (embryonic leaves) and flower buds. The primordia and buds then are dormant until spring, when they give rise to leaves and flowers (4). 

Bloodroot (Sanguinaria canadensis)

Another early spring bloomer, bloodroot is named for the red sap that fills its roots, flower stalks and leaf stalks. It emerges a little earlier than Dutchman's breeches, but the two overlap in their flowering time. Bloodroot is pollinated primarily by mining bees, but also by cuckoo bees, bee flies and sweat bees (5). 

Left to right: Bloodroot flowering in mid-April; elongated capsules maturing in mid-May; brown seeds with white elaiosomes in early June. 

Initially, bloodroot leaves are wrapped around flower stalks like cloaks, but eventually they unfurl, flatten and expand. Unlike Dutchman's breeches, bloodroot leaves persist until late summer before they die back..

In early to mid summer, bloodroot flowers are replaced by elongated capsules full of ant-dispersed seeds. Like Dutchman's breeches, bloodroot seeds have attached elaiosomes (eh-LAY-oh-sohms, literally "fat bodies"), They look like tiny worms, but these plant tissues are full of protein and fat that entice ants to carry the seeds to their nest, detach the elaiosomes to feed to their larvae and leave the seeds to germinate in a presumably safer place. 

Where to Find Spring Ephemerals

Wherever there are native deciduous forests, there should be spring ephemerals. Visit Scientific and Natural Areas and state and regional parks, such as Nerstrand Big Woods State Park in southeast Minnesota, Elm Creek Park Reserve in Maple Grove, or Mille Lacs Kathio State Park near Onamia. 

White trout lily (Erythronium albidum) flowering near Mille Lacs Kathio State Park in late April.

There are many more places to enjoy spring ephemerals. To find them, visit iNaturalist and look up the species described above (or others), or use the Minnesota Natural Resource Atlas. To use the atlas, open the Mapping Tool, choose Add Layers from the Options menu box, and in the Biota category choose Native Plant Communities -- Parks & Trails. Zoom in and look for areas of Mesic Hardwood Forest System.

Wisconsin and Iowa are also good places to look for spring ephemerals. A quick search finds that, in Wisconsin, the Northwoods Wildlife Center near Minocqua and Rib Mountain State Park near Rib Mountain are full of spring ephemerals. The Iowa DNR has a webpage dedicated to Woodland Wildflowers & Reports. The listed sites are from 2025, but the same should be true for 2026. 

References

1. The pollination ecology of Dicentra cucullaria. Lazarus Walter Macior, American Journal of Botany, Vol. 57, No. 1. 1970. 

2. Flowering ecology of some spring woodland herbs. Douglas W. Schemske and others. Ecology, Vol. 59, No. 2. 1978.

3. Myrmecochory: How Ants Shape Plant Communities. Julie Michaelson, Xerces Society. 2024. 

4. Dicentra cucullaria. Flora of North America, Vol. 3. Website accessed 2-17-26.

5. Pollinators of Native Plants: Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants. Heather Holm. Pollination Press, LLC. 2014. Available here and at some libraries.

Native Plant Seed Germination: Some Resources

There's something deeply satisfying about growing plants from seeds. More than cuttings or divisions, seeds hold the promise, or at least the potential, for new life. 

Most seeds packaged for sale in retail stores are easy to germinate. They might take a week or more to emerge, but they don't require special treatment other than adequate warmth, moisture, oxygen and sometimes light.

Seeds purchased from native plant nurseries or collected from wild native plants often need more attention. Many of these seeds are dormant, meaning they won't germinate even in favorable conditions. It's an adaptation that prevents the seeds from germinating when the seedlings are unlikely to survive, such as in late fall heading into winter.

Causes and Treatments

Seed dormancy has many causes, and different species have different causes. For example, the seeds of ironweed, Vernonia fasciculata, need cold, moist conditions for a month or two before they'll germinate. That's likely due to immature embryos that need time to develop and/or chemical inhbitors that must leach out or otherwise diminish in concentration before the embryos can grow (1). 

Ironweed flowers in late summer and early fall with brilliant purple heads of flowers. These plants were about 6 feet tall. Eventually the heads fill with bundles of seeds that are wind-dispersed.

Nature provides those conditions over winter, but the seeds can also be treated artificially. In a process called cold-moist stratification, the seeds are placed in a damp medium or on damp filter paper and refrigerated for some length of time. How long the seeds must be stratified depends on the species. For ironweed, it's one or two months.

Another example is smooth wild rose, Rosa blanda. The small, seed-like fruits, called achenes (ah-KEENs) of this native shrub are doubly dormant, meaning they have two types of dormancy that must be overcome before the seeds will germinate. In this case, the embryos are immature even when the hips are red and ripe, In addition, the seeds are surrounded by a hard pericarp, or fruit wall, that physically prevents germination (2).

Smooth rose blooms in late spring and early summer. Rose hips ripen in early fall, Each hip contains several small, seed-like fruits called achenes.Each achene has a hard fruit wall, or pericarp.

In nature, the double dormancy of the achenes is broken by up to two years of cold (winter) and warm (summer) conditions. The seeds then germinate the second spring after they are produced. 

Artificial treatment of the achenes begins with scarification, a wearing away of the pericarp by immersing the achenes in boilng water, rubbing them lightly with sandpaper, or using other methods.  Then the seeds are stratified in alternating temperatures, starting with cold-moist stratification, then warm-moist stratification (60-70 F), then another cold-moist stratification (3, 4). The Propagation Protocol Database (5) recommends one month of warm-moist stratification followed by four months of cold-moist stratification. 

Seed dormancy is a complex topic involving biochemistry, ecology and evolution. To learn more about it and to learn how to break the seed dormancy of particular species, see the reference sections after Cited References.

Cited References

1. Germination of Native Prairie Forb Seeds. J.T. Sorensen and D.J. Holden. Journal of Range Management Volume 27, No. 2. 1974.

2. Seed Germination within Genus Rosa: The Complexity of the Process and Influencing Factors. Roxana L. Stoian-Dod and others. Horticulturae Vol. 9, No. 8. 2023.

3. Smooth Rose (Early Wild Rose, Meadow Wild Rose, Labrador Rose). G.D. Bebeau. The Friends of the Wildflower Garden, Inc. Trees & Shrubs of the Eloise Butler Wildflower Garden. 2013. 

4. Rosa blanda, Early Wild Rose. Prairie Moon Nursery. Website accessed December 24, 2025. 

Seed Dormancy References

Understanding Seed Dormancy and Germination Requirements of Rare Plants. Dustin Wolkis, Center for Plant Conservation. 2022.

Seed Dormancy: What Is It? SeedImages.com, Colorado State University. Website accessed December 20, 2025. 

Seed Dormancy Mechanisms. SeedImages.com, Colorado State University. Website accessed December 20, 2025.

Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. Carol C. Baskin and Jerry M. Baskin. 2nd edition. 2014. Academic Press, San Diego. (This is a textbook available through several booksellers.)

The evolution of seed dormancy: environmental cues, evolutionary hubs, and diversification of the seed plants. Charles G. Willis and others. New Phytologist Vol. 203, Issue 1. 2014. 

Species-Specific Methods to Break Dormancy

Propagation Protocol Database. Native Plant Network. Search for the plant of interest by entering its genus, then choose the species.

Prairie Moon Nursery. The website for this Minnesota-based native plant nursery includes germination information for many species. Search for and select the species of interest, then look for a table entry called Germination Code. See also their list of seeds that need no treatment.

Native Seed Propagation Methods. This guide from the Missouri Botanical Garden includes instructions for many methods of breaking seed dormancy, along with specific treatments for selected native plants. Some of the species listed may not be native to the Minnesota region.

Yes, These Are Flowers

The whitish, stalked, bud-like structures at the base of this common blue violet (Viola sororia) are flowers, and at about half an inch long, this is as big and showy as they get.

Unlike the blue-purple flowers that bloom in spring, these flowers start to appear in summer and last into fall. They have little or no pigment, reduced or no petals, and no nectar. They don't need these things because they don't need to lure insect pollinators. They never open, so they pollinate themselves.  

In botanical terms, these closed flowers are cleistogamous (kly-STOG-amus), meaning "closed marriage." In contrast, the showier flowers of spring are chasmogamous (kaz-MOG-amus), meaning "open marriage."

Each type of flower can benefit the plant. The chasmogamous ones are cross-pollinated by insects, potentially mixing genes from different parents as pollen is carried from plant to plant. The resulting seeds grow into offspring that have gene combinations different from their parents and from each other, potentially giving them new traits that improve their survival and reproduction. 

That's an advantage if their environment changes over space or time. In a population, more genetic variation among individuals increases the odds that at least a few of them will have the traits needed to grow in uneven or changing conditions. 

The downside is that chasmogamous flowers are expensive. The plants spend much of their stored energy making pigments for petals, sugars for nectar, and longer stalks to lift the flowers to leaf height or above, where they will attract pollinators. If something happens to the flowers -- if they're eaten by an herbivore or if pollinators don't visit, for example -- that energy is wasted. That also puts the next generation at risk. If there are no seeds, there are no offspring.

The chasmogamous (open) flowers of common blue violet attract insect pollinators. The blue-purple pigments, darker nectar guides on the lower petal, and hairs on the lateral petals take much of the plant's stored energy to produce. 

Cleistogamous flowers provide a back-up, among other benefits. In terms of energy, they're much less expensive to make, and they don't rely on pollinators to make seeds. That's an advantage if the chasmogamous flowers are missing or aren't pollinated, because the plants have another way to produce seeds. It's a second chance.

Because they're self-pollinated, cleistogamous flowers produce seeds and offspring that are genetically identical to the parent and to each other. That's beneficial if environmental conditions are favorable and stable. If the parent is genetically well-adapted to the conditions, then the offspring will be, too, because those genes are preserved by self-pollination.

Self-pollination can also help get rid of versions of genes, called alleles (ah-LEELS), that reduce fitness, i.e., successful growth and reproduction. Cross-pollination can mask these harmful alleles by contributing healthier ones from other plants, thereby blunting any deleterious effects. Self-pollination, though, increases the odds that the effects of the alleles, now not partnered with more favorable ones, will show up in a plant's anatomy or physiology. That's bad for individuals that die or are unable to reproduce as a result, but the loss of those individuals can eliminate the responsible alleles from a population.  

Genetic uniformity can be a disadvantage, too, especially if conditions vary across a habitat or if they change over time.. A new environment may require adaptations the population doesn't have, because the plants are genetically identical. For example, if conditions are warmer and drier but the offspring come from a parent adapted to cooler, wetter conditions, they may not reproduce or even survive. 

Another potential disadvantage of cleistogamy is inbreeding depression, the loss of fitness that can result from maladaptive alleles that aren't "weeded out" by self-pollination, as described above. Also, although cleistogamous flowers usually produce more seeds than chasmogamous ones, the seeds tend to be dispersed closer to the parent plant, which can increase competition among siblings (1). 

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If you find cleistogamous flowers in violets or other plants, you'll be looking at something really old. Cleistogamy developed about 100 million years ago in some of the first flowering plants and has developed in many species since then. According to one estimate, worldwide there are at least 693 species of cleistogamous plants in 50 families (1). That was in 2007; more cleistogamous plants might have been discovered or confirmed since then. 

Although cleistogamy is present in a minority of plants, its long persistence among many species suggests that it has improved plant reproduction and survival. In at least 50 families, these plants converged independently on the same solution to the challenges of floral reproduction. That's profound, even amazing -- in a colorless, nectarless, inconspicuous kind of way.

Cited Reference

1) Theresa M. Culley and Matthew R. Klooster. The Cleistogamous BreedingSystem: A Review of its Frequency, Evolution and Ecology in Angiosperms. The Botanical Review 73 (1): 1-30. 2007. 

Additional References

Anne L. Sternberger and others. Environmental impact on the temporal production of chasmogamous and cleistogamous flowers in the mixed breeding system of Viola pubescens. PLoS One 15 (3). 2020. 

M.W. Austin, P.O. Cole, K.M. Olsen, and A.B. Smith. Climate change is associated with increased allocation to potential outcrossing in a common mixed mating species. Am J Bot.109(7): pp.1085-1096. 2022. 

Theresa M. Culley. Reproductive Biology and Delayed Selfing in Viola pubescens (Violaceae), an understory herb with chasmogamous and cleistogamous flowers.International Journal of Plant Sciences 163 (1): pp. 113-122. 2002. [Available to view with a free JSTOR account.]

Plant Profile: Ragweeds

 Common ragweed, Ambrosia artemisiifolia, and great ragweed, A. trifida.

Common ragweed, Ambrosia artemisiifolia, flowering in late August. 

For people with seasonal allergies, ragweeds are beasts.

Pollen from these plants, also called hay fever weeds, cause much of the sneezing, watering eyes, coughing, wheezing and other symptoms that torment allergy and asthma sufferers in late summer and early fall.

Both great ragweed and common ragweed, the two species frequently found here, are native annuals. They’re often found along roadsides, in abandoned lots, along field edges and in other disturbed places. Most seeds germinate in early spring, but some may germinate as late as July. Flowering peaks in August and September and lasts until the first frost.

Common ragweed plants are 1-3 feet tall at maturity. Leaves are opposite below and alternate above, divided and deeply lobed, to 6 inches long and 4 inches wide at the base.

Great ragweed is 3-12 feet tall at maturity. Leaves are opposite, the lower ones three-lobed and the upper ones simple and ellpitical. Largest leaves grow up to 12 inches long and 8 inches wide.

Ragweeds produce separate staminate (male, or pollen-producing) and pistillate (female, or seed-producing) flower heads on spike-like racemes. Both kinds of flowers are found on the same plant; in other words, the plants are monoecious (mo-NEE-shus). Staminate flowers are grouped into stalked, downward-facing heads on the upper part of each raceme. Pistillate flowers are clustered below, often nestled in leaf axils.

After pollination, pistillate flowers develop small diamond- or top-shaped fruits with a central “beak” surrounded by ridges, each ridge ending in a short spine. The fruits look like miniature crowns, so ragweeds are also called crown weeds. Each fruit contains a single seed, and an individual plant of either species can produce thousands of seeds each season. Common ragweed seeds are viable in soil for two to three years and up to 40 years (3). Giant ragweed seeds are less durable; most lose viability after one year (4).

 

Left: Great ragweed racemes are 3-8 inches long. Right: Closer view of ragweed flower heads. Staminate heads are stalked and face downward. Pistillate heads contain only one flower. The one at the arrow has been pollinated and a young, green fruit is developing. Common ragweed racemes are shorter but otherwise similar.

Both types of flowers are small and simple; they have no large, colorful petals. That’s because the plants are primarily wind-pollinated and therefore don’t invest in structures needed to attract insects. Typical of wind-pollinated plants, the staminate flowers produce tremendous amounts of pollen. Many sources state that a single plant can release up to 10 million pollen grains a day and up to 1 billion grains a year.

It’s unclear where those numbers come from, but recent studies confirm similarly large amounts. In France, where ragweed is introduced and invasive, researchers found that a single common ragweed (A. artemisiifolia) produces from 100 million to 3 billion pollen grains per season (1). A study of intact vs. mowed common ragweed in Quebec found that an intact plant produces more than 100 million pollen grains per season (2).

These great ragweed leaves are dusted with yellow pollen.

Those millions of grains, multiplied by the number of plants that can densely fill an optimal habitat, present a serious health threat to people with ragweed allergies. The plants do have some ecological benefits, however. As colonizers of disturbed places, they can hold soils in place as other plants succeed them. In addition, their protein- and oil-rich seeds are eaten by migrating and winter-resident song birds and game birds, as well as by chipmunks, voles, and other rodents.

Beastly or beneficial, ragweeds are an enduring part of our landscape. Maybe that’s why Linnaeus put them in the genus Ambrosia, Greek for “immortal,” “divine,” or “food of the gods.” Given the seeminly unending symptoms ragweed pollen can cause, the first meaning, immortal, seems to fit. The last two, though, are hard to fathom. Ragweeds are indeed persistent. But for allergy sufferers, they are anything but divine.

References 

1. Boris Fumanal, Bruno Chauvel, François Bretagnolle. 2007. Estimation of the pollen and seed production of common ragweed in Europe. Annals of Agricultural and Environmental Medicine (AAEM) 14 (2), pp. 233-236.

2. Simard M.J., and Benoit, D.L. 2011. Effect of repetitive mowing on common ragweed (Ambrosia 
artemisiifolia L.) pollen and seed production. Annals of Agricultural and Environmental Medicine (AAEM)18 (1), pp. 55–62.

3. Cornell College of Agriculture and Life Sciences. Common ragweed. Website accessed 9/5/25.

4. The Ohio State University. College of Food, Agricultural, and Environmental Sciences. Giant ragweed: A weed of extremes. 9/27/16.

Where to Find Remnant and Restored Prairies in Minnesota

A restored prairie at Elm Creek Park Reserve, Maple Grove, MN.

On a windy summer day, a Minnesota prairie looks like an ocean. The tallest grasses move like waves, their stems bending, rebounding and bending again, an imaginary sea of grass. 

For prairie plants, bending without breaking isn’t just a metaphor for survival; it is survival, one of many adaptations for life in a dry, often windy, fire-prone upland. These forces have literally shaped the grasses that dominate the landscape. Their narrow leaves minimize water loss, their low growing points help them recover after fire or grazing, and their deep roots serve to both anchor and absorb. (See this illustration of prairie plant root systems.)

Among the grasses are a variety of forbs, non-woody plants other than grasses. Depending on the site, there may be pasque flowers (Anemone patens), lupine (Lupinus perennis), butterfly milkweed (Asclepias tuberosa), prairie clovers (Dalea species), boneset (Eupatorium perfoliatum), gentians (Gentiana species), sunflowers (Helianthus speces) and many others, each flowering in its own season.

From left: Prairie larkspur (Delphinium carolinianum), butterfly milkweed, and bottle gentian (Gentiana andrewsii).

 
They're all part of Minnesota's northern tallgrass prairie, part of a larger grassland biome in the central United States and south­ central Canada. Northern tallgrass once covered roughly 18 million acres in the southern and western parts of the state. About 235,000 acres remain, less than two percent of the original area.

 

The Minnesota DNR's map of original prairie (yellow) and remaining prairie (red).The original, readable map is here.  

That's not much, but there are still places to find remnants and restorations of this now-limited ecosystem. Here are some resources to help find them.

The Minnesota DNR's Prairie Finder maps public lands you can visit to explore prairies. These are state parks, historic sites, national wildlife refuges and other places where prairie is protected or restored for education, research, and enjoyment. One such place is the Northern Tallgrass Prairie National Wildlife Refuge in western Minnesota. 

The U of M's Minnesota Natural Resource Atlas is an interactive map that allows you to search for native prairies and other natural resources in the state. At the website, select the Interactive Map and choose Add Layers. In the pull-down menu, check the box for Native Prairie in the Biota category and wait for the map to load. Keep in mind that some of the prairies are on private land.

In the Twin Cities area, Three Rivers Park District has restored about 1,600 acres of prairie. Crow-Hassan Park Reserve in Hanover, Murphy-Hanrehan Park Reserve in Savage and Carver Park Reserve in Victoria have the largest holdings. Entry to the parks is free. Public seed collections in late summer and fall help support additional restoration.

This recently burned prairie at Crow Hassan Park Reserve is already growing back, and with vigor. This is lupine, Lupinus perennis.

 
The Prairie Wetlands Learning Center, part of the Fergus Falls Wetland Management District, showcases the eastern-most part of the prairie pothole region, a mix of shallow wetland depressions and upland prairie. Trails are open to the public any time. Call for Visitor Center hours. The Learning Center also offers programs for students and teachers.

If you can't visit a prairie but want to see one, you can go there virtually. Minnesota Scientific and Natural Areas Virtual Visits can take you to several, such as Bluestem Prairie near Glyndon and Lost Valley Prairie near Hastings. The websites for many state parks also offer virtual tours of their lands, such as Buffalo River State Park's panoramic views of Prairie View Trail and Big Sky Trail.

Another option is to view the PBS video Life of a Prairie, about a private, undisturbed prairie in western Minnesota. For a compilation of information about prairies, including some great photography, see the DNR's Prairie Stories. 

Fungi as Fixers

The plants in this restored prairie at Elm Creek Park Reserve are mostly mycorrhizal. Fungi live with their roots in a mutually beneficial relationship.

The last post introduced mycorrhizae, the fungus-root associations that benefit both partners. The fungus transports nutrients and water to the plant, while the plant gives sugars and other carbon-containing molecules to the fungus. Most plants are mycorrhizal and are dependent on this symbiosis for their best growth.

On a larger scale, mycorrhizae are also important in ecological restoration, the practice of regenerating native plant communities after they’ve been degraded or destroyed. They may also help with carbon sequestration, in this case the storage of carbon in fungal mycelia, the underground bodies of fungi.

Mycorrhizae and Ecological Restoration

In a 2023 review article, a team of scientists led by Lisa Markovchick wrote about a gap between the science and practice of using mycorrhizae in restoration projects. Although research supports such use, practice lags, in part because of negative views of fungi as only pathogens.

To counter this perception, Markovchick and her collaborators offer insights from research and tips for both protecting mycorrhizal fungi and deploying them during restoration projects. A few of those insights and tips are below. Links to Markovchick’s full paper and a webinar summarizing her work follow the list.

According to Markovchick and her collaborators:

• Mycorrhizae perform many functions, such as promoting water infiltration and retention, preventing erosion, and boosting plant nutrition, survival, and resilience.
• Mycorrhizal fungi also have roles in providing ecosystem services, such as responding to disturbance and providing habitat for other organisms, thereby enhancing biodiversity.
• Change in land use, drought, invasive plants, and other disturbances can deplete mycorrhizal fungi or change the fungal species present. Even some necessary practices, such as applying herbicides to invasive plants, can affect mycorrhizae.
• The benefits of mycorrhizal fungi are clear from many studies. For example, they can significantly increase species richness (the number of different plant species in a community), and plant biomass, and their effects tend to grow with time.
• There must be a good match between plants and mycorrhizal fungi when both are used to restore a community. Mass-produced mycorrhizal fungi may not provide that important pairing, leading to neutral or negative results. Introducing fungi from a native community near the restoration site has proven most beneficial.

References

The Gap Between Mycorrhizal Science and Application. Wild Earth Guardians YouTube video featuring Lisa Markovchick. 53:46.

The gap between mycorrhizal science and application: existence, origins, and relevance during the United Naton’s Decade on Ecosystem Restoration. Lisa M. Markovchick, Vanessa Carrasco-Denney, Jyotsna Sharma, and others. Restoration Ecology Vol. 31, No. 4. May 2023.

 

Mycorrhizae and Carbon Sequestration

Potential solutions to a warming climate include nature-based options such as protecting forests, grasslands and wetlands. Protecting and enhancing mycorrhizal growth could be another solution, because plants transfer carbon-containing compounds such as sugars to below-ground fungal bodies (mycelia) and the roots they support.

The carbon that builds those compounds comes from atmospheric carbon dioxide captured during photosynthesis, and it can be a significant amount. In a 2023 review article, Heidi-Jayne Hawkins and others estimate that, globally, about 13 gigatons of carbon dioxide equivalents are transferred to the mycelia of mycorrhizal fungi each year. That amounts to about 36 percent of the carbon dioxide emissions from fossil fuels in 2021.

Living mycelia can also promote long-term carbon storage by releasing sugars and acids from their hyphae (the fungal strands that constitute the mycelium). These compounds eventually lead to the formation of mineral-associated organic matter, or MAOM. In this type of soil organic matter, carbon compounds are bound to clay, silt, or other mineral particles in soils. MAOM is slower to decompose, in part because it’s protected inside mineral aggregates that are harder for decomposers to access.

Even after fungal mycelia die, they can support carbon storage. Their organic matter is added to the soil, where it can attract soil particles and form the enlarging aggregates that stabilize carbon as MAOM.

The authors emphasize that there is more to understand about the flow of carbon into and through mycorrhizae and its effects on carbon sequestration. Still, they consider mycorrhizal fungi “a major carbon pool.”

Reference

Mycorrhizal mycelium as a global carbon pool. Heidi-Jayne Hawkins, Rachael I.M. Cargill, Michael E. Van Nuland, and others. Current Biology, Volume 33, Issue 11. June 5, 2023.

How can we support mycorrhizal fungi?

 Lisa Markovchick’s article recommends several actions and tips to improve the diversity and function of mycorrhizae, specifically in natural areas. A few of them are below. For a full list, see the link above.

• Protect source populations of mycorrhizae. Native communities with little or no history of disturbance are refuges for these fungi.
• When restorations are planned, include steps for soil conservation.
• Choose mycorrhizal fungi that are appropriate for the plant species being restored. This could be accomplished by introducing the “full diversity” of fungi from nearby native communities like the one being regenerated.
• Plants and their mycorrhizal fungi won’t associate unless both are alive and come into direct contact. Timing and placement are important, as is the source of fungi. Commercial mycorrhizal products may be a poor choice.

Nature's Ancient Engineers

Young mushrooms of fly agaric, Amanita muscaria, in a northern Minnesota mixed coniferous-deciduous forest.The caps of the mushrooms will flatten and expand up to 10 inches wide.

Chances are, you recognize this mushroom. Fly agaric has long been known for its colorful cap, its hallucinogenic effects, and its supposed ability to attract and kill flies. It has also found its way into popular literature and media; It’s the Alice in Wonderland mushroom, the place where Smurfs live, and the Super Mushroom in Super Mario Bros. games. Unfortunately for some, it’s also poisonous, even deadly (1, 2).

Less known but much more significant is what fly agaric does below ground. The mushroom is just the visible part, the body that produces spores for reproduction. Underneath it is an extensive network of thread-like strands called hyphae (HY-fee), together called the mycelium (my-SEE-lee-um). The hyphae are like hunter-gatherers; they run through the soil and absorb water and nutrients to support the rest of the fungus.

Fly agaric also needs organic (carbon-containing) molecules, such as sugars and amino acids, the building blocks of proteins. Many fungi obtain these by breaking down dead organic matter in the soil. Fly agaric, though, goes about it differently: It barters with living plants.

The one above likely does business with white pine (Pinus strobus), red pine (Pinus resinosa), paper birch (Betula papyrifera) or quaking aspen (Populus tremuloides) in the northern Minnesota forest where it grew (3). Beneath the surface, its mycelium wraps around the tips of the trees’ roots, forming a sheath. Some of the hyphae in the sheath grow into the root and form a net around some of the cells. That’s where the exchange occurs: The fungus gives water and nutrients to the plant, while the plant gives organic molecules to the fungus. 

Illustration of an ectomycorrhiza, which forms a sheath around root tips. Hyphae cross the epidermis and enter the root cortex. There they form a net, called a Hartig net, between the cells. The unit of measurement in the upper right scale is 100 microns. One hundred microns is the approximate width of a human hair. The photographs are colorized images produced by a scanning electron microscope, or SEM. Illustration by Atrebe10, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license, via Wikimedia.

This symbiotic relationship is called a mycorrhiza (MY-co-RY-za), literally “fungus root.” The sheathing type, called an ectomycorrhiza, is relatively new, about 200 million years old give or take a few million years. An older type, roughly 400 million years old, doesn’t sheath a plant’s roots but instead grows inside the root cells themselves, where the exchange of nutrients, water and organic compounds occurs. This type is called an endomycorrhiza or arbuscular mycorrhiza, the latter named for the tree-like growth, called an arbuscule, the fungus forms inside the cells.

Development of mycorrhizae (plural, ending in -zee) was critical to the transition of plants from water to land hundreds of millions of years ago (4, 5 7). These early land plants had no roots or vascular (conducting) tissues. Those that eventually developed symbiotic associations with fungi had an advantage, because mycorrhizae could extend the plant's reach into the soil to obtain water and nutrients. Mycorrhizae were so beneficial that they developed independently many times over, involving different plants and fungi (6).

Given that far-reaching history, it’s no surprise that there are more types of mycorrhizae than the two described above. Ecto- and endomycorrhizae are the most common, but there are at least two more types (6). Whatever the type, in most cases both partners benefit and often are dependent on each other for survival. Without their association, neither partner would thrive. Their ecosystems wouldn’t, either.

That’s because approximately 80% of modern terrestrial plants are mycorrhizal, although the percentage of such plants in a community can vary (7). Prairies, deciduous forests, coniferous forests, and other terrestrial ecosystems are generally dominated by mycorrhizal plants. They are the foundation of these systems, supporting all the trophic (feeding) levels above them. A mycorrhizal white pine, for example, grows the cones that hold the seeds that feed a variety of birds and mammals, which in turn have their own roles in their communities.

Mycorrhizae are so important to ecosystems that restoring highly disturbed places, such as mines and abandoned agricultural fields, can be helped by adding mycorrhizal fungi to soils or seeds when restoration begins. Mycorrhizae have also been suggested as possible remedies for high carbon dioxide levels in our atmosphere, because they can help move carbon below ground. These practices will be the subjects of the next post.

References

1.      Two cases of severe Amanita muscaria poisoning including a fatality. Ethan M. Meisel, MD, and others. Wilderness and Environmental Medicine, Vol. 33, No. 4, 2022.

2.     Notes from the field: Acute intoxications from consumption of Amanita muscaria mushrooms — Minnesota, 2018. Joanne Taylor and others. MMWR Morb Mortal Wkly Rep 2019, Vol. 68: pp. 483–484, 2019.

3.     Fungus associates of ectotrophic mycorrhizae. James M. Trappe. Botanical Review, Vol. 28, No. 4: pp. 538-606, 1962. Available for reading with a free JSTOR account at https://www.jstor.org/stable/4353659.

4.     The origin and evolution of mycorrhizal symbioses: from palaeomycology to phylogenomics. Christine Strullu-Derrien and others. New Phytologist, Vol. 220, No. 4: pp.1012-1030, 2018.

5.      History of mycorrhizae. Jake Sun, Lindenwood University. The Confluence, Vol. 1, No. 2: Art. 2, 2022.

6.      Mycorrhizal Fungi. Society for the Protection of Underground Networks. Website accessed February 3, 2025.

7.      Coevolution of roots and mycorrhizas of land plants. Mark C. Brundrett. New Phytologist, Vol. 154, No. 2: pp. 275-304, 2002. 

Are Fungi Plants?

In early classification systems, these morel mushrooms (Morchella esculenta) were included with plants.

 
At one time, morel mushrooms and other fungi were considered plants. That was when all life was classified as either plant or animal, and morels sure didn’t look like animals. They emerge from the soil, they don't move, and they produce “fruiting” bodies (mushrooms) for reproduction. In addition, its cells are surrounded by rigid walls, as are the cells of ferns, grasses, trees and other living things that are true plants. (Most bacterial cells also have walls, but that's another topic.)

It wasn’t until the 1960s that fungi were placed in their own kingdom. Ecologist Robert Whittaker thought they should be separated from plants because they are decomposers, not producers. In other words, they break down and absorb organic matter, whereas plants make organic matter by photosynthesis. In ecologists’ terms, fungi are saprotrophic (literally, rot feeders) whereas plants are autotrophic (self-feeders). There are exceptions in each group, but they’re in the minority.

Other differences became apparent as the decades went by. Fungal cell walls, for example, are made of chitin, long chains of modified glucose molecules. That’s the same material that forms the exoskeletons of insects. Plant cells, however, are mostly cellulose, twisted and bundled chains of glucose without the modifications present in chitin.

Other differences appear inside their cells. Fungal cells have no chloroplasts, the organelles where photosynthesis takes place. They also lack chlorophyll, the green pigment primarily responsible for absorbing light energy. That makes sense, since fungi aren’t photosynthetic.

Plant cells (left, from a moss) contain chloroplasts, the green organelles where photosynthesis takes place. Fungal cells (right, from a Morchella, or morel, mushroom) do not. This is one difference between plants and fungi. Moss cells: Kelvinsong, CC BY 3.0, via Wikimedia Commons. Morchella cells cropped from image by Marc Perkins CC BY-NC 2.0, via Flickr.

There are other differences, but maybe these are enough to show that fungi and plants aren’t closely related. Even so, the line between them can be muddy. Some older botany textbooks include at least a chapter about fungi. And as mentioned above, mushrooms and other large reproductive bodies are still called “fruiting” bodies, even though they’re not at all like the fruits produced by flowering plants.

It can be confusing. What’s not confusing or unclear is that fungi, though not plants, are important to plants for many reasons. For example, fungi made it possible for plants to colonize land, a step in development not only for plants but for entire terrestrial ecosystems. More on that in the next post.

Plants for Bee Specialists

Jerusalem artichoke, Helianthus tuberosus, is one of several sunflower species favored by the sunflower mining bee, a specialist pollinator.

The sunflower mining bee, Andrena helianthi, has discriminating tastes.

This native bee is a specialist, gathering pollen primarily from plants in the aster family, Asteraceae (formerly Compositae, also called composites). To be more specific, it favors pollen from plants in the genus Helianthus, the sunflowers, to feed its larvae. (1).

In pollinator terminology, the sunflower mining bee is oligolectic, meaning “few chosen.” It’s far from alone in having narrow food preferences. According to the recent Minnesota Statewide Bee Survey (2), about 30% of the nearly 360 bee species confirmed in the survey are oligolectic.

Benefits and Drawbacks of Oligolecty

Given that high number, there must be advantages to oligolecty. One possibility is that the bees co-evolved with a few host plants that offer more digestible pollen (3). Entomologists at the University of Wisconsin found that the larvae of the blueberry mason bee, Osmia ribifloris, thrived when fed preferred host pollen that also included the microbes naturally found in that pollen. In contrast, larvae fed microbe-free pollen from the preferred host plant were much less fit, and larvae fed pollen from non-host plants had intermediate fitness (4).

Plants benefit from the relationship, too. Species visited by oligolectic bees have dedicated pollinators that transfer pollen among only a few kinds of plants, which makes successful pollination more likely. The plant loses less pollen to insects that carry it to a wider variety of plants, most of which can’t use it.

The potential disadvantage for both oligolectic bees and their plant hosts is that if either one becomes rare, its partner could become rare, too. A spiraling decline of both bees and plants happens when, for example, a plant population is displaced by an invasive species or fails to thrive in a warmer or wetter environment. As the plant becomes less abundant, so does the oligolectic bee that depends on it. In turn, as the oligolectic bee becomes less abundant, so can the plant that depends on it for pollination. If fewer seeds are produced, the population may decline further, with consequent effects on the oligolectic bee, and so on. It’s a vicious circle that can be difficult to interrupt.

The Habitat Solution

Difficult but not impossible. The answer is to provide habitat, including preferred host plants, for the sunflower mining bee and other oligolectic species. Fortunately, there are several resources to learn which plants or groups of plants benefit which bee species.

Entomologist and ecologist Jarrod Fowler compiled a list of bee specialists documented in the Central U.S., a region that includes Minnesota, Iowa, Wisconsin, North Dakota, and South Dakota (3). He also tabulated their preferred plant(s) and found that species in the aster or sunflower family, Asteraceae, and the bean or pea family, Fabaceae, were visited most frequently by specialist bees in this region.

In addition, he noted the top 25 genera that support oligolectic bees. The genera found in this region include Helianthus (sunflowers), Heterotheca (false goldenasters), Solidago (goldenrods), and Symphyotrichum (asters).

Although Helianthus is a favorite of sunflower mining bee, the insect has also been collected from the flowers of (l to r) cup plant (Silphium perfoliatum), New England aster (Symphyotrichum novae-angliae) and goldenrod (Solidago) species, here showy goldenrod (S. speciosa).(1)

The Minnesota Department of Natural Resources’ Minnesota Bee Species List is another useful resource (5). The list of around 460 bees includes both those that collect pollen and those that are parasites on other bees’ nests. For those that collect pollen, the table provides the species’ lecty (range of pollen preference, either oligo- or poly-) and its nesting habitat, if either is known.

The species list in the Minnesota Statewide Bee Survey (2) includes not only the bees’ names and lecty, if the latter is known, but also the ecological province(s) where each species was found. The report includes distribution maps of the bee species as well as their conservation status, or S-rank, which can range from S1 (critically imperiled) to S5 (secure).

The 2024 Featured Plant series from the Board of Water and Soil Resources (6) highlights several plants that support specialist bees or other insects. A Featured Plant is posted online at the beginning of each month.

If you observe and photograph bees visiting plants, consider submitting your records to iNaturalist. Several bee-related projects are hosted on this online platform, including Minnesota Native Bees. To find other projects, go to the iNaturalist website, choose Projects from the Community drop-down menu, and type “bees” into the search box.

Who knows, maybe the sunflowers you watch this summer and fall will host sunflower mining bees. Although the bees were uncommon to rare in the state’s bee survey, you could be the lucky one who spots this specialist pollinator.

References

1)  Andrena helianthi, Robertson 1891. Discover Life. Website accessed July 3, 2024.

2)   Minnesota Statewide Bee Survey 2014-2023. Minnesota Department of Natural Resources.

3)   Pollen Specialist Bees of the Central United States. Jarrod Fowler, 2020.

4)   Dharampal, P.S., Hetherington, M.C., and Steffan, S.A. 2020. Microbes make the meal: oligolectic bees require microbes within their host pollen to thrive. Ecological Entomology 45: 1418-1427. DOI: 10.1111/een.12926. https://par.nsf.gov/servlets/purl/10253224

5)    Minnesota Bee Species List. Minnesota Department of Natural Resources, August 2023.

6)     Board of Water Resources Featured Plant series, 2024. (Red-berried elder is the July featured plant; plants featured in earlier months are in the Featured Plant archive.)

Plant Profile: Wild Ginger

A single flower emerges between a pair of leaves of wild ginger, Asarum canadense.

In spring, wild ginger is one of the first plants to emerge on the deciduous forest floor. Softly hairy leaves grow in pairs from shallow rhizomes, eventually expanding into heart- or kidney-shaped blades 3-5 inches wide. Mature petioles, or leaf stalks, are several inches long, and like the leaves, they are finely white-hairy. To an imaginative observer, they resemble pipe cleaners.

A single, reddish-brown, tubular flower develops in the axil of each pair of leaves. The flower is close to the ground on a slightly bent peduncle, or flower stalk. The flower has no petals, but its three, long-pointed sepal resemble petals and curve back over an open floral cup.

Inside the cup, the stigmas – the parts that receive pollen – mature first. They’re in the center of the flower, supported by their styles and surrounded by 12 stamens. Initially the stamens bend down and away from the stigmas, their pollen-bearing anthers lying parallel with the bottom of the cup. Over several days, the stamens straighten.

This dissected flower shows a central column of several upright stamens (solid arrow) surrounding stigmas and styles, which are hidden. The whitish dust around the top of the column is pollen. Several anthers still rest on the bottom of the cup (dashed arrow). 

Left: A flower with most stamens upright and a few still lying on the bottom of the floral cup.
Right: An older flower with all stamens upright.

A Pollination Puzzle

Pollination is a bit of a mystery. Many general references say the flowers are pollinated by flies and ground beetles attracted to the flowers’ fleshy color and supposed rotting-meat odor. As it turns out, that’s an assumption passed from one reference to the next, but it’s easy to see why it persisted.

Wild ginger doesn’t look like something pollinated by bees or butterflies. Although the flowers are beautiful in their details, they’re generally drab and mostly hidden under the leaves. They don’t look anything like the brightly colored, conspicuous flowers typically pollinated by bees or butterflies. Instead, their maroon to brown color matches that of animal flesh, like the flowers of some other plants pollinated by flies.

The bright yellow flowers of marsh marigold (Caltha palustris), left, are typical those pollinated by bees and other insects. The flower structure of skunk cabbage, center, looks and smells like decaying animal flesh and is pollinated by flies. Wild ginger, right, more closely resembles a fly-pollinated flower, at least in color. Photos not to scale. Skunk cabbage photo © 2009 Katy Chayka at Minnesota Wildflowers, used with permission granted on the website. 

Skunk cabbage (Symplocarpus foetidus), another Minnesota native, is a good example. It emerges in late winter or very early spring, even while snow covers the ground. Its flowering structure is a reddish-brown, leaf-like spathe enclosing a club of flowers called a spadix. As the plant’s name suggests, the structure has a fetid, dead-skunk smell. The small flowers on the spadix are pollinated by flies and beetles drawn to the plant’s carrion-like color and odor.

Other Evidence

Wild ginger doesn’t smell that bad. A sniff test finds that, at worst, the flowers can have a slightly unpleasant odor, but they don’t smell so strongly of rotting carcass that you would recoil. “Earthy” might be the best word to describe it. Some even say the flowers have a sweet smell. In any case, they aren’t obvious fly bait.

Early studies of wild ginger find other contradictions with the fly-pollination hypothesis. In the late 1940s, Harvey E. Wildman of the University of West Virginia experimented with wild ginger flowers to answer the question of how they’re pollinated (1). He removed the stamens from one group of flowers and left another group intact. In each group, he covered some of the flowers in wax paper bags (after ensuring no insects were inside the flowers) and left others uncovered. After several weeks, he checked the flowers for seed development.

None of the flowers with stamens removed, even those that were uncovered, developed seeds. In fact, all such flowers he checked had either fallen off or withered. In contrast, most of the flowers left intact developed “sound seeds.” That includes the ones that were covered. Wildman also reported that few insects were found inside any of the flowers.

If the flowers were strictly cross-pollinated by flies or other insects, at least some of the uncovered ones without stamens would have developed seeds, because something would have brought pollen to their stigmas. At the same time, the intact, covered flowers would not have developed seeds, because insects did not have access. Wildman concluded that wild ginger is primarily self-pollinated, not cross-pollinated.

Timed for Cross-Pollination?

Although Wildman’s experiment is illuminating, pollination is still a head-scratcher. One way plants foster cross-pollination is by staggering the development of stigmas and anthers inside a single flower, and wild ginger does exactly that. As mentioned above, the stigmas mature first, Eventually the filaments and anthers straighten and approach the stigmas, but not before the flowers have had a chance to receive pollen from another plant. This suggests that self-pollination is a back-up rather than a primary means of fertilization. Are we missing a pollinator? 

Whether self-pollinated or somehow cross-pollinated, fertilized flowers later develop seeds within capsules. When the capsules open in mid-summer, they expose small seeds with tiny fat bodies attached. The bodies, called elaiosomes (e-LY-oh-somes or e-LAY-oh-somes) attract ants, which carry the seeds back to a nest, eat the elaiosomes or feed them to their young, and leave the seeds to germinate, safely out of reach of seed predators. Seeds can also fall next to the parent plant and germinate there.

Left: The swollen ovary at the base of the flower indicates that this flower has been fertilized. Center: The same flower viewed from above. Each of the twelve dots around the center is what remains of a stamen. Right: Seeds are released in mid-summer. Each is just a few millimeters wide and long, with a golden-brown elaiosome attached. 

Rhizomes for Spread, Not for Spice

A rhizome of wild ginger (arrow).

If its seeds don’t succeed in helping wild ginger reproduce, its rhizomes can. (See the previous post for more about rhizomes.) The plant is almost aggressive in its vegetative spread, quickly filling suitable habitat, especially where it has limited competition.

Many say the rhizomes are aromatic and ginger-y in smell and taste. Although they have a long history of use as medicine and flavoring, ingesting them in any form is discouraged now. Wild ginger rhizomes and other parts have been found to contain variable amounts of aristolochic acid, a compound known to damage kidneys and perhaps cause cancer (2, 3). Handling the plants can also cause dermatitis.

This isn’t true of ginger roots (rhizomes) or ginger spice found in grocery stores. Culinary ginger is “true” ginger, Zingiber officinale, a tropical plant. It is not related to Asarum canadense.

Where to Find Wild Ginger

Wild ginger is native to deciduous and mixed deciduous-coniferous forests. It prefers full to part shade and moist, humus-rich soils. It wilts in prolonged drought. 

Wild ginger range in the upper Midwest and North America. Maps from USDA NRCS Plants Database (4).

Cited References

1)      Wildman, Harvey E. 1950. Pollination of Asarum Canadense L. Science 111 (2890): 551. http://www.jstor.org/stable/1676584.

2)      McMillin, D.L., Nelson, C.D., Richards, D.G., and Mein, E.A. 2003. Research Report: Determination of Aristolochic Acid in Asarum canadense (Wild Ginger). Meridian Institute.

3)      Qingqing Zhou, et al. 2023. Overview of aristolochic acid nephropathy: an update. Kidney Res Clin Pract 42 (5): 579-590.

4)      USDA, NRCS. 2024. The PLANTS Database (http://plants.usda.gov, 05/01/2024). National Plant Data Team, Greensboro, NC USA.

Other References and More Information

Anderson, M.K. Ed. 2000, 2003 and 2006. Plant Guide: Canadian Wildginger. USDA NRCS National Plant Data Center, Davis, California.

Baskin, J. M., & Baskin, C. C. 1986. Seed Germination Ecophysiology of the Woodland Herb Asarum canadense. The American Midland Naturalist, 116 (1), 132–139. https://doi.org/10.2307/2425945

Dunphy, S.A. Meadley, K. M. Prior, and M.E. Frederickson. 2016. An invasive slug exploits an ant-seed dispersal mutualism. Oecologia 181: 149-159. DOI 10.1007/s00442-015-3530-0 .

Hayden, W. John. 2010. Don't Judge a Book by its Cover: The Curious Case of Wild Ginger Pollination. Bulletin of the Virginia Native Plant Society 29 (1): 1, 6.

Schultz, K. 2014. Using shade to propagate Canadian wild ginger (Asarum canadense L.) and other woodland forbs. Native Plants Journal 15 (3): 231-235. DOI: https://doi.org/10.3368/npj.15.3.231.

Stritch, L. No date. Plant of the Week: Wild Ginger (Asarum canadense L.). USDA, US Forest Service.