Friday, November 11, 2022

Oriental Bittersweet in Winter

Oriental bittersweet fruits on bare winter vines twining around a shrubby host.
The yellow capsules and scarlet arils of Oriental Bittersweet stand out in winter.

Oriental, Asian or Asiatic Bittersweet (Celastrus orbiculatus) is an introduced vine that can girdle or smother its hosts. Efforts to remove this invasive plant are complicated by its similarity to native American Bittersweet (C. scandens).

Fortunately, mature female vines of each species are noticeably different, especially in fall and winter. Open this updated post from January 2021 to learn how to tell them apart. A two-page ID guide is free to download. 

Thursday, October 27, 2022

What is Tar Spot?

 Silver maple leaves fallen on grass. The leaves have several large, dark spots on the upper surface of the blades.

The black scabs on these Silver Maple leaves are signs of tar spot, a common fungal disease that also affects Norway, Red and other maples as well as willows, holly and sycamores.

The spots, called stromata, are the overwintering form of the fungus. When infected leaves fall, they often land with their upper surfaces, and so the stromata, facing up. That puts them in a good position to release wind-borne or rain-splashed spores next spring. The freed spores then infect new leaves, eventually producing light green to yellow spots on the blades that enlarge as the season progresses. The spots turn dark and tarry-looking in late summer and early fall. 

Although it looks bad, tar spot is rarely a serious disease. It can cause early leaf drop, but otherwise it's just unsightly. Raking and destroying infected leaves can prevent reinfection in ­­spring. In most cases, fungicides are not recommended.

Inside a Stroma

If you slice through a stroma in spring and examine it with a microscope, you'll find its lower surface covered with tiny, bowl-shaped structures called apothecia. Inside each apothecium are hundreds of  sacs called asci ("as-eye" or "ask-eye," singular ascus). Each ascus contains eight needle-shaped spores that are released through cracks in the overlying stroma. 

Left: An apothecium of Rhytisma acerinum with the dark, overlying stroma ruptured. A clear layer of asci covers the bottom of the apothecium. Right: A closeup of the asci with emerging needle-like spores. Both photos by Bruce Watt, University of Maine, 

Because tar spot fungi need living tissue to survive, spores are not released in fall. Instead, they are released in spring, when leaves are emerging from their buds. Blown by wind or launched by splashes of water, many of the spores won't land on a susceptible host. With a good measure of luck, some will, and the life cycle begins again.  

The "Womb" Fungi

Tar spot fungi are in the genus Rhytisma. Three species typically infect maples: native R. americanum and R. punctatum and introduced R. acerinum.

All three species belong to a large group of fungi called Ascomycetes, or sac fungi. The apothecia of sac fungi typically are open at the top, but those of Rhytisma are covered by a layer of fungal tissue in the stromata. 

Because the protected apothecia resemble wombs, they're also called hysterothecia, from the Greek root words "hystero," meaning uterus or womb, and "theca," meaning case or cup.


Leaf Diseases of Hardwoods: Tar Spots. Dr. Robert Blanchette, College of Food, Agriculture and Natural Resources, University of Minnesota.

Tar Spot of Trees and Shrubs. Brian Hudelson, University of Wisconsin-Madison Plant Pathology. Last Revised 12/18/2018. 

Rhytisma acerinum and Rhytisma punctatum, two causes of Tar Spot of maple. Heather Hallen Adams and Tom Volk, University of Wisconsin-LaCrosse. Fungus of the Month, October 2007. 


Wednesday, October 12, 2022

Are Psyllids the Solution to Invasive Knotweeds?

Help is on the horizon to manage these aggressive plants.
Fallopia japonica  (Houtt.) Ronse Decr., Japanese Knotweed
Fallopia sachalinensis (F. Schmidt) Ronse Decr., Giant Knotweed
Fallopia x bohemica (Chrtek & Chrtkov√°) J.P. Bailey, Bohemian Knotweed

A stand of Japanese Knotweed, Fallopia japonica, with bare remains of inflorescences.
A stand of Japanese Knotweed in October. Although these plants are green, others are starting to yellow. The spiky growths are inflorescences that have shed their flowers and fruits.

In Minnesota and around the world, invasive knotweeds are some of the most difficult plants to manage.

Aided by vigorous rhizomes that can extend several meters from a parent plant (1, 2), Japanese Knotweed, Giant Knotweed and their hybrid, Bohemian Knotweed, can displace native plants, change soil chemistry, alter microbe and invertebrate assemblages, and enhance soil erosion, especially on riverbanks (3, 4, 5). In addition, they are potentially allelopathic, meaning they can release compounds from living or decaying tissues that inhibit the growth of some plants (6, 7).

Knotweeds are spreading in North America and elsewhere, and as they do, so is the realization that controlling them is no easy task. (See EDDMapS for their distributions in North America; use the genus Reynoutria, a synonym.) Although a variety of chemical and mechanical control methods can be effective, all require years of repeated efforts and monitoring for renewed growth (8). Mechanical methods – digging and cutting – also demand meticulous attention, because fragments of rhizomes or stems left behind can regenerate the plants (9).

A large stand of Knotweed, Fallopia species, at the edge of a property. The plants extend into an adjacent paved trail.
This large stand of Knotweed covers about 2,000 square feet along a property edge. The property is adjacent to a lake, offering the riparian habitat where knotweeds thrive and spread. 

Biocontrol – the use of a plant’s natural enemies – now offers some hope for an efficient alternative. Small, sap-sucking insects called Knotweed Psyllids, Aphalara itadori, have been collected from Japan, part of knotweeds’ native range. After years of study to determine that the insects would effectively target only knotweeds, scientists released the psyllids into several field locations in North America.  

According to the North American Invasive Species Management Association (NAISMA, 10), one race of the psyllids, called the Kyushu line, was released on Japanese and Bohemian Knotweed populations in several states in 2020 and 2021. (Minnesota was not one of them.) Another race, called the Hokkaido line, was released on Giant Knotweed populations in 2021. The nymphs and adults feed on knotweed stems and leaves, removing sap from the plants and causing the leaves to curl. The insects leave behind lerp, a flaky or stringy crystallized form of honeydew, a sugary solution they excrete.

When winter arrives, the adult psyllids take shelter and enter diapause, a time of suspended activity. Because the insects are native to a similar climate in Japan, it is hoped the adults will survive winters here and resume activity in spring, as they do in their original range. However, according to NAISMA, no sustained populations have been confirmed. Additional races or populations are being studied for future release.  

Although psyllids are not yet a sure solution to knotweed invasions, the research is promising. It also highlights the importance of accurate plant identification, because different races of psyllids are effective on different knotweeds. The Kyushu race is more effective on Japanese and Bohemian Knotweed, whereas the Hokkaido race is better for Giant Knotweed. A third race, called the Murakami line, is being studied for release on Bohemian knotweed in Canada.

In Minnesota, Japanese, Giant and Bohemian Knotweed are on the state Department of Agriculture’s noxious weed list. They are classified as “prohibited-control,” meaning all propagating parts, including seeds and vegetative parts, must be prevented from spreading. In practice, that means treating at least the above-ground growth before the stems flower in late summer, and if the stems are cut, collecting and disposing of the cuttings so they don’t escape and establish knotweed stands elsewhere.

In other words, it’s a lot of work, especially in large patches. With some additional research and field tests, psyllids may someday make that work easier.

Resources for Knotweed Identification and Management

Grevstad, F.S., J.E. Andreas, R.S. Bourchier, and R. Shaw. 2022. Knotweeds (Fallopia spp.): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2022-19-KNOTWEEDS-P. [Accessed online at 23198.pdf (]

Dusz M-A, Martin F-M, Dommanget F, Petit A, Dechaume-Moncharmont C, Evette A. Review of Existing Knowledge and Practices of Tarping for the Control of Invasive Knotweeds. Plants. 2021; 10(10):2152.

Minnesota Department of Natural Resources. Non-native knotweeds: Japanese, Bohemian, and Giant knotweed. Website accessed October 10, 2022.

Mary H. Meyer, University of Minnesota Extension Service. Japanese knotweed, a major noxious weed. October 6, 2020.

Angela Gupta, Amy Rager and Megan M. Weber, University of Minnesota Extension Service. Japanese knotweed. Reviewed in 2019.

Minnesota Department of Agriculture. Knotweeds. (Brochure.) No date.

Minnesota Department of Agriculture. Japanese Knotweed. Website accessed October 10, 2022.

Minnesota Department of Transportation. Minnesota Noxious Weeds. February 5, 2020.

Linda M. Wilson. British Columbia Ministry of Forests and Range. Key to Identification of Invasive Knotweeds in British Columbia


1) Grevstad, F.S., J.E. Andreas, R.S. Bourchier, and R. Shaw. 2022. Knotweeds (Fallopia spp.): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2022-19-KNOTWEEDS-P. [Accessed online at 23198.pdf (]

2) Fennell M, Wade M, Bacon KL. 2018. Japanese knotweed (Fallopia japonica): an analysis of capacity to cause structural damage (compared to other plants) and typical rhizome extension. PeerJ 6:e5246

3) Lavoie, C. 2017. The impact of invasive knotweed species (Reynoutria spp.) on the environment: review and research perspectives. Biological Invasions 19: 2319-2337.

4) Matte, R., Boivin, M., and Lavoie, C. 2021. Japanese knotweed increases soil erosion on riverbanks. River Research and Applications 38 (3): 561-572. DOI: 10.1002.rra.3918

5) Colleran, B., Lacy, S.N., and Retamal, M.R. 2020. Invasive Japanese knotweed (Reynoutria japonica Houtt.) and related knotweeds as catalysis for streambank erosion. River Research and Applications 36 (9): 1962-1969. DOI: 10.1002/rra.3725.

6) Kato-Noguchi, H. Allelopathy of Knotweeds as Invasive Plants. Plants 2022, 11, 3. DOI: 10.3390/plants11010003.

7) Drazan, D., Smith, A.G., Anderson, N.O., Becker, R., and Clark, M. 2021. History of knotweed (Fallopia spp.) invasiveness. Weed Science 69(6): 617-623. DOI: 10.1017/wsc.2021.62.

8) Grevstad, F.S., J.E. Andreas, R.S. Bourchier, R. Shaw, R.L. Winston, and C.B. Randall. 2018. Biology and Biological Control of Knotweeds. USDA Forest Service, Forest Health Assessment and Applied Sciences Team, Morgantown, West Virginia. FHTET-2017-03. [Accessed online at]

9) Lawson JW, Fennell M, Smith MW, Bacon KL. 2021. Regeneration and growth in crowns and rhizome fragments of Japanese knotweed (Reynoutria japonica) and desiccation as a potential control strategy. PeerJ 9:e11783

10) USDA. Field Release of the Knotweed Psyllid Aphalara itadori (Hemiptera: Psyllidae) for Classical Biological Control of Japanese, Giant, and Bohemian Knotweeds, Fallopia japonica, F. sachalinensis, and F. x bohemica (Polygonaceae), in the Contiguous United States. Environmental Assessment, January 2020.

11) Grevstad, F.S., J.E. Andreas, R.S. Bourchier, and R. Shaw. 2022. Knotweeds (Fallopia spp.): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2022-19-KNOTWEEDS-P. [Accessed online at 23198.pdf (]

Monday, September 19, 2022

Plant Profile: Ghost Plant, Monotropa uniflora

 This forest native has no chloroplasts and can't photosynthesize. How does it survive? By cheating.

A clump of Ghost Plant soon after emerging, with several nodding, white stems.
Ghost Plant, Monotropa uniflora L.

Ghost Plant, also called Wax Plant, is well named. It looks like something fashioned, if not out of ether, then out of a chunk of paraffin and an active imagination.

Resembling a fungus more than a flowering plant, its pale, waxy stems and scaly leaves have no chloroplasts. They were lost somewhere along the plant’s evolutionary pathway, yet it manages to survive without being able to make sugars by photosynthesis. At first Ghost Plant was thought to be saprophytic, absorbing nutrients from decaying organic matter in its surroundings. That’s what fungi do, and it made sense that this plant, so similar in appearance, would do the same.

Each stem bears a nodding flower. 

From Partner to Parasite

Scientists then found that its roots, like those of most plants, don’t work alone. They are covered with and invaded by fungi, beneficial partners that reach farther into the soil to collect and transport nutrients, especially nitrogen and phosphorus, back to the plant.

These associations between fungi and roots, called mycorrhizae (MY-co-RY-zee, literally “fungus roots”), typically benefit both partners. The plant receives nutrients gathered by the fungus, and the fungus receives photosynthate made by the plant. It’s a textbook example of mutualism, a type of symbiosis in which both organisms gain something from their relationship.

Ancestors of Ghost Plant might have started out that way, with both the plant and the fungus sharing something with the other. Somewhere along the line, though, the relationship changed.  When Ghost Plant lost its chloroplasts, it could no longer give photosynthate to its fungal partner. The two-way relationship became one-way, and Ghost Plant behaved more like a parasite.

As a result, some of those fungal partners probably dropped off. With nothing to feed them, the fungi don't benefit from the relationship, and their association with Ghost Plant likely dwindled from a diverse many to a select few that either best met the plant’s needs or that failed to detect the ruse and avoid becoming hosts (1).

Tapping the Connection

Ghost Plant’s mycorrhizae are now associated only with fungi in the genus Russula, a group of mushroom-forming decomposers found all over the world (2). Russula also forms mycorrhizae with other plants -- green plants, plants that photosynthesize and send sugars to the fungus and then to Ghost Plant, if it’s joined to the same network.

Like tapping into a phone conversation, Ghost Plant takes some of what’s exchanged – in this case, sugars and nutrients – to support itself, without giving anything in return. It’s an adaptation that helps the plant survive in the deep shade of forest interiors. No need to grow tall or early or to develop leaves that can tolerate shade. Just plug into the web of connections between plants and fungi and take what’s needed.

The technical term for this is myco-heterotrophy, “myco” meaning fungus and “heterotroph” referring to organisms that feed on others. Ghost Plant is one of only 400 or so plants around the world that are fully myco-heterotrophic, meaning they spend their entire lives feeding on others through mycorrhizal connections (1).

Some scientists simply call the plant a parasite, either on the fungus or on the green plants connected to it. Others, citing the plant’s pickpocket habit, choose a more colorful term: Cheater.

Description and Range

Ghost Plant emerges and flowers in late summer. Each hooked stems bears a single flower at its tip. After flowering, the stems straighten and develop capsules full of tiny seeds. For more help with identification, see the Minnesota Wildflowers page for this species.

After flowering, the stems straighten and the flowers later develop capsules (right) with many seeds.

In Minnesota, Ghost Plant is mostly a northern species, but it’s also found in scattered counties in the south. It also grows in most of Wisconsin and generally in forests throughout the U.S. and Canada. According to Nature Serve Explorer and the Global Biodiversity Information Facility, Ghost Plant is also found in Central America, South America, Europe and Asia.

Cited References

1) Merckx, V., Bidartondo, M.I., Hynson, N.A. 2009. Myco-heterotrophy: when fungi host plants. Annals of Botany 104 (7): 1255-1261. doi: 10.1093/aob/mcp235

2) Massicotte, H.B., Melville, L.H., and Peterson, R.L. 2005. Structural features of mycorrhizal associations in two members of the Monotropoideae, Monotropa uniflora and Pterospora andromedea. Mycorrhiza 15: 101-110. DOI: 10.1007/s00572-004-0305-6

Additional References

Dance, A. 2017. Inner workings: Special relationship between fungi and plants may have spurred changes to ancient climate. Proceedings of the National Academy of Sciences USA 114(46): 12089-12091. Accessed online on 9/12/22 at

Van der Heijden, M.G.A., Martin, F.M., Selosse, M.-A., Sanders, I.R. 2015. Mycorrhizal ecology and evolution: the past the present, and the future. New Phytologist Foundation 205 (4): 1406-1423.

Monday, August 29, 2022

Plant Profile: Wild Cucumber

This native vine is aggressive but not invasive in North America. The story is different overseas.

A wild cucumber vine with upright clusters of white flowers.
Wild Cucumber, Echinocystis lobata (Michx.) Torr. & A. Gray. This vine was growing over vegetation in a wet prairie.

Wild Cucumber, also called Wild Balsam Apple, is a native, annual vine of riverbanks, lakeshores, wetland edges and damp forest edges. It’s especially evident in late summer, when its long vines produce upright racemes of white flowers. (See Flower Parts for Plant ID for an explanation of racemes and other inflorescences.)

The vines are fast-growing, even aggressive, and where several get started, they can swamp whatever they’re growing on, including other plants. The sight of them covering a tree, shrub, or garden can be alarming – some say creepy – but according to the experts, there’s little to fear.

In late summer, Wild Cucumber produces upright racemes of white flowers. Staminate (male) and pistillate (female) flowers are separate, but on the same plant. To use the botanical term, the plant is monoecious (mo-NEE-shus).

Because Wild Cucumber is a native plant, it’s had a long time to fit in. Throughout its natural range in most of the U.S. and Canada, it’s adapted to the other things it lives with, and they are adapted to it. The vines may overgrow and perhaps smother its host plants, but because of these mutual adaptations, overall, Wild Cucumber is not considered a threat.

A soldier beetle collecting pollen from staminate flowers.

In other words, although Wild Cucumber can be aggressive, it’s not invasive. The latter term is reserved for plants (or animals) that are both introduced and aggressive. They’re new to an ecosystem, and for a variety of reasons, they have a competitive advantage. For example, they may grow fast, reproduce prolifically, have extended growing seasons or have few pests and diseases, so they can easily displace other plants and disrupt ecosystems.

That isn’t happening here, but in Central Europe, Wild Cucumber is a pest. In Hungary, Poland, Austria and other countries, Wild Cucumber was introduced as an ornamental and escaped cultivation. It has invaded rivers valleys, lakeshores and wetlands, forming dense mats that block light from reaching native European plants. By 2014, the plant had become such a problem that it was considered “one of the 100 most dangerous invasive plant species in Europe” (1).

It's possible to anticipate and even prevent such problems. Invasive plants have some characteristics in common, and studying them can predict how a plant will likely behave if it’s introduced outside its native range.

Here are some of the characteristics of Wild Cucumber that make it invasive in Europe (1).

  • It has a broad native range
  • It can adapt to a range of environments.
  • It is a human commensal, meaning it benefits from association with humans.
  • It grows fast.
  • It reproduces in abundance, in this case by seeds.
  • Its seeds remain viable for more than a year.

Many of the same characteristics are found in other plants that are invasive. Common Buckthorn (Rhamnus cathartica), for example, also has a broad range – across Europe – and can grow in several habitats. This shrub or small tree was brought to North America as a hedge plant and escaped. A female can produce hundreds to thousands of seeds, and they are viable for up to five years. Common Buckthorn forms dense stands that displace other plants, and it has become a scourge of many forested ecosystems.

By comparison, Wild Cucumber is mostly harmless, at least here. It will flower for a few more weeks before forming prickly, oval “cucumbers” that are not edible. The seeds will shoot out of the fruit in autumn, overwinter, and germinate in spring. That's a good time to remove the seedlings if you don't want them. Wild Cucumber is an annual, so the parent vine will die after one season.

For more information about how to identify Wild Cucumber, see this page from Minnesota Wildflowers


(1) CABI Invasive Species Compendium. Echinocystis lobata (wild cucumber). Accessed August 19, 2022.

Sunday, July 31, 2022

How to Identify Native and Introduced Phragmites

A colony of Phragmites grasses with last year's panicles.
Phragmites australis subsp. americanus. Photo taken in early August in southern Minnesota.

Update: An abbreviated ID guide (PDF) is here

Phragmites or Common Reed, Phragmites australis, is a 12- to 18-foot tall, perennial grass of wetlands, shorelines and ditches. Two subspecies are common in the U.S. One is the native subspecies americanus; the other is the introduced subspecies australis.

Both subspecies grow in colonies, but subspecies australis is more aggressive and can dominate habitats to the near exclusion of other plants. For that reason, there is growing interest in identifying and mapping subspecies australis to determine the extent of its spread and to target those colonies for removal.

Although the subspecies look alike, there are several characteristics that, taken together, can identify one from the other. The most reliable characteristics are shown below, after a few terms used to describe grass stems, leaves and flowers.

Stems and leaves

A panel of two photos labeling the culm, blade, sheath and ligule.

The culm is the stem of a grass. Grasses have round culms that are hollow between the nodes, the swollen areas on a culm. The leaf blade is flat and ribbon-like, whereas the leaf sheath wraps around the culm below the blade. Where the blade meets the sheath, most grasses have a ligule, a membrane or hairy fringe visible when the blade is pulled away from the culm.


Grass flowers, called florets, are specialized for wind pollination. Each floret is composed of two narrow bracts, a lower lemma and an upper palea. Stamens and feathery stigmas emerge from between them.

Florets are arranged in small spikes called spikelets. At the base of each spikelet are two bracts called glumes. Glume length differs between the subspecies of Phragmites. More on that in a following section. 

Spikelets of Smooth Brome, Bromus inermis, are shown below. On the left are spikelets with brown anthers and feathery, white stigmas emerging from individual florets. On the right is a single spikelet spread apart to see the florets and glumes. The spikelets are about  3 cm (1.5 in.) long. 

A panel of two photos showing spikelets of smooth brome, with glumes and florets labeled.

Phragmites characteristics

To identify Phragmites subspecies, it’s best to look at more than one plant in a colony and at several characteristics of each plant. Hybrids are possible, but they’re said to be rare. 


To see ligules, pull back a blade from the middle third of the culm. (Ligules may be immature on the upper third of the culm and degraded on the lower third.) Ligule length differs between the subspecies. 

Subspecies americanus: 1-2 mm long, brown, become darker and smudgy in late summer and fall. The photo below was taken in early August.

Subspecies australis: 0.5-1 mm long, appearing as a thin, brown line. The photo below was taken in early July.

A panel of two photos showing the ligules of subspecies americanus and australis.

Stem color and texture
In summer and fall, examine the base of the culm. Be sure to look at the culm and not the sheath, if one is present. The photos below are from early July.

Subspecies americanus: Lower culm is smooth, somewhat glossy, often red.
Subspecies australis: Lower culm is ridged, not glossy, often green fading to brown.

The smooth, red lower stem of subspecies americanus and the green, ridged lower stem of subspecies australis.


In late summer, fall and early winter, examine the lower stem for the presence of leaf sheaths. The photos below are from mid-November.

Subspecies americanus: Sheaths are absent or easily removed.
Subspecies australis: Sheaths are persistent and harder to remove. 

The bare stem of subspecies americanus compared to the sheathed stem of subspecies australis in November.


In late summer and fall, measure glume length. By late fall some of the florets may be gone, but the glumes often persist. It's best to look at several pairs of glumes to get an idea of their average length. The photos below are from mid-November.

Subspecies americanus: Lower glume 3-6 mm long (most > 4mm); upper glume 5-11 mm long (most > 6 mm).
Subspecies australis: Lower glume 2.5-5 mm long (most < 4 mm); upper glume 5-8 mm long (most < 6 mm).

The glumes of subspecies americanus and australis along a metric ruler.


In late winter, spring or early summer, look at last season's panicles, the plume-like clusters of Phragmites spikelets. The photos below are from early July.

Subspecies americanus: Panicles bare, thinner, less branched.
Subspecies australis: Panicles fuzzier, thicker, more branched.

A panel of two photos contrasting the panicles of subspecies americanus and australis.


Amur Silver Grass and Reed Canary Grass are two smaller grasses that can be mistaken for Phragmites. 

Amur Silver Grass, Miscanthus sacchariflorus, is an introduced grass that has silvery-white panicles in late summer and fall. It grows 6-8 feet tall, shorter than Phragmites, and its leaf blades have a white midrib. Its ligules are a greenish-white, hairy fringe. The photos below were taken in early August.

A panel of two photos showing a colony and a ligule of Amur Silver Grass.
Amur Silver Grass plants and ligule.

Reed Canary Grass, Phalaris arundinacea, blooms in spring, not late summer, with smaller panicles that eventually contract. It's shorter than Phragmites, growing up to 5 feet tall. Its ligules are membranous and 3-8 mm long. 

A panel of two photos showing a colony and a ligule of Reed Canary Grass.
Reed Canary Grass colony and ligule.


Chadde, S.W. 2012. Wetland Plants of Minnesota. 2nd edition (revised). A Bogman Guide.

Judziewicz, E. J., Freckmann, R.W., Clark, L.G., and Black, M.R. 2014. Field Guide to Wisconsin Grasses. The University of Wisconsin Press, Madison.

Minnesota Aquatic Invasive Species Research Center (MAISRC). Identifying invasive Phragmites. Website accessed July 2022.

Swearingen, J., Saltonstall, K., and Tilley, D. Phragmites Field Guide: Distinguishing Native and Exotic Forms of Common Reed (Phragmites Australis) in the United States. Technical Note Plant Materials 56, October 2012. USDA Natural Resources Conservation Service, Boise, ID.

Saturday, July 16, 2022

Plant profile: Enchanter's Nightshade


A group of Enchanter's Nightshade with racemes of small, white flowers.
Enchanter's Nightshade, Circaea lutetiana L., in July. 

Enchanter’s Nightshade, Circaea lutetiana, doesn’t get a lot of positive attention. This native plant of the forest floor is often regarded as a weed, something to remove in favor of less aggressive, more attractive species. Its appearance is modest at best. Its name, though, suggests something less humble. What’s the story?

Mostly Inconspicuous

Compared to showier spring wildflowers, this summer bloomer isn’t much to look at. Individual stems grow up to a foot tall, sometimes longer, with opposite, egg-shaped leaves and smooth stems. The plant spreads with rhizomes to form colonies, especially in disturbed areas or canopy gaps where more light reaches the understory.

In July and August, Enchanter’s Nightshade produces small, white flowers on racemes. If not for their masses, the flowers would be easy to miss. Each is just a few millimeters across, smaller than an eraser on the end of a pencil, with a mere two sepals, two petals, two stamens and one pistil. They're beautiful, but minimal. 

Small, pear-shaped fruits follow. They’re covered with hooked hairs that grab onto anything that passes – shoelaces, socks, pants, fur. It’s impossible to ignore them, but it’s not the kind of attention that inspires admiration. A few steps through a patch catches a load of little stickers.

Flowers and fruits of Enchanter's Nighshade.

From Meek to Mythical

The ”enchanter” in the plant’s name is Circe, the sorceress of Greek myth. According to legend, she used herbs and potions to turn people into pigs, lions and wolves. One of the herbs in her concoctions was Circaea lutetiana, the plant that now bears her name. The species name lutetiana also reflects the plant’s supposed use in sorcery. Lutetia was the ancient city that is now Paris, France, called “the city of witches” in some accounts.

Studies of the plant’s chemistry don’t find much that is bewitching. Although it’s called a nightshade, it’s not a traditional member of that group. Nightshades are usually plants in the tomato family, Solanaceae (solan-AY-see-ee). In terms of chemistry, this family is known for its higher quantities of alkaloids, compounds that have uncertain roles in plants but a variety of physiological effects in humans. Some alkaloids, such as opium from poppies and cocaine from coca bushes, are mind-altering, euphoric and addictive.

In contrast, Enchanter’s Nightshade is in the evening primrose family, Onagraceae. Its chemistry features flavonoids, molecules that have various functions in plants. Some are pigments – the red of raspberries, for example – while others regulate growth or protect against UV radiation, among other roles (1, 2). Like alkaloids, flavonoids have potential use in medicine, but they aren’t mind-altering, and they aren’t associated with euphoria. In fact, they’re relatively benign. Circe might have worked some legendary magic, but Enchanter’s Nightshade wouldn’t have put much punch in her potions.

Adaptation and Potential Advantage

The ”nightshade” in its name, then, probably comes from its shady habitat. Like other plants of the forest floor, Enchanter’s Nightshade is adapted to an environment with limited light. One adaptation is its ability to colonize gaps or disturbances by growth if its rhizomes, underground stems that produce shoots along their length.

Unlike other clonal plants, Enchanter’s Nightshade holds some of that ability in reserve. Its new rhizomes do not produce shoots. Instead, they lengthen and branch until late summer, when some of them produce small tubers called hibernacles at their tips. Eventually the hibernacles are separated from the parent plant and from each other and go dormant. They are the vegetative equivalent of seeds, but with faster development the following spring to form patches of upright stems. In higher light intensities, this growth can be vigorous (3). 

Near the end of the season, tips of rhizomes (arrow) develop into tuber-like hibernacles.
The hibernacles overwinter and resume growth next spring, forming new rhizomes and
above ground shoots.

Although some consider that growth weedy and aggressive, it could prove useful. Restorationists are looking at Enchanter’s Nightshade and other “weedy natives” as potential cover crops where severe infestations of invasive plants have been removed. By shading out or otherwise competing with invasive plants that can reoccupy an area, Enchanter’s Nightshade may give native communities an improved chance to recover (4). 

It’s not magic, but it could be transformative. If research shows this to be an effective restoration technique, Enchanter’s Nightshade could help convert a landscape from diminished to diverse. 


(1) Falcone Ferreyra, M.L,  Rius, S.P., and Casati, P. (2012). Flavonoids: biosynthesis, biological functions, and biotechnological applications. Frontiers in Plant Science volume 33, article 222.

(2) Panche, A. N., Diwan, A. D., and Chandra, S. R. (2016). Flavonoids: an overview. Journal of nutritional science, 5, e47.

(3) Verburg, R.W., and During, H.J. (1998). Vegetative propagation and sexual reproduction ­in the woodland understorey pseudo-annual Circaea lutetiana L. Plant Ecology 134: 211-224.

(4) Reinartz, J., White, M., and Hapner, J. No date. A role for native weeds and aggressive plants for replacing (or competing with) invasives in badly degraded areas. Invasive Plants Association of Wisconsin. Accessed online on 7/13/22 at A Role for Native Weeds - Invasive Plants Association of Wisconsin (

Oriental Bittersweet in Winter

The yellow capsules and scarlet arils of Oriental Bittersweet stand out in winter. Oriental, Asian or Asiatic Bittersweet ( Celastrus orbicu...