Friday, January 6, 2023

What Is a False Terminal Bud?

A basswood winter twig with red lateral and terminal buds.


On trees and shrubs, a false terminal bud is a lateral bud at the end of a twig. Unlike a true terminal bud, it doesn’t enclose the growth at the tip of a stem or branch.

This happens in some species when growing shoots don’t harden off in fall. Instead, their stems die back, leaving the end-most lateral buds to take over as the last buds on the twigs.  

According to several keys, false terminal buds are found only on woody plants with alternate lateral buds. The stems of plants with opposite buds may also wither or die back before winter, but the end-most pair of buds are not called false terminal buds. 

This difference may seem trivial, but some winter keys use false and true terminal buds to separate species into groups or to confirm a plant’s identity. Fortunately, with a hand lens and some practice, there are reliable ways to recognize each.


True terminal buds

Consider a stem of a deciduous (leaf-shedding) tree or shrub with alternate leaves along its length and a growing shoot at its tip. By mid-summer, the plant begins forming buds in leaf axils, the angles between leaves and stems. These are axillary or lateral buds, also called leaf buds. When leaves are shed in fall, their petioles (leaf stalks) leave marks below these buds, called leaf scars.

At the same time, growth stops at the tip of the stem and the young shoot is enclosed in either bud scales or protective leaves. This is a true terminal bud (c). It has no leaf scar (b) below it, and it is often larger than lateral buds (a). 

A diagram of a branch that develops a true terminal bud, labeled "c," and lateral buds and leaf scars, labeled "a" and "b."
I

















False terminal buds

Now consider a stem that, instead of forming a terminal bud, dies back to the closest lateral bud. This is a false terminal bud. It has a leaf scar below it and is about the same size as other lateral buds.

The stub of the withered stem may project above the base of the bud on the side opposite the leaf scar. The mark it leaves, called a branch scar (b), can be mistaken for a leaf scar, but it won’t have vascular bundle scars. This can be hard to see without a hand lens. Also, in some species with false terminal buds, the bud is noticeably angled toward or away from the twig (a).

A diagram of a branch that develops a false terminal bud, labeled "a," and the branch scar that sits above the base of the bud, labeled "b."


Examples

Black Walnut (Juglans nigra) is a tree with alternate buds (a) and heart-shaped or three-lobed leaf scars. The true terminal bud (b) is larger than the lateral buds and does not have a leaf scar. The last lateral bud (c) sits just below the terminal bud. 

A series of three photos showing lateral and true terminal buds of black walnut.




American Elm (Ulmus americana), another tree with alternate buds, has false terminal buds. In the photos below, a branch scar is evident above the base of the bud (a) and a leaf scar (b) is on the opposite side, below the bud. Like some other species with false terminal buds, the bud is angled. 

A series of three photos showing the false terminal bud, leaf scar and branch scar on a winter twig of American elm.













Silver Maple (Acer saccharinum) is a tree with opposite or paired lateral buds (a) and a true terminal bud (b) that is larger than the lateral buds and has no leaf scar (c). The last pair of buds (d) sits just below the terminal bud. 

Two photos showing the true terminal bud, opposite lateral buds and leaf scars on a winter twig of silver maple.











Basswood (Tilia americana) is a tree with alternate lateral buds and false terminal buds. Below, the false terminal bud has a leaf scar (a) and is about the same size as the lateral bud below it. The branch scar (b) is smaller and darker than the leaf scar. 

A panel of three photos showing the false terminal bud, leaf scar and branch scar on a winter twig of basswood.












Highbush Cranberry (Viburnum trilobum, V. opulus) is a shrub with opposite buds. It does not form terminal buds of any kind. Instead, in fall, the ends of the stems (a) wither back to the last pair of opposite buds (b), which will resume growth in spring. As this pattern repeats, the shrub branches in a Y-shaped form called sympodial growth (c).



Two photos showing stems of highbush cranberry withered back to the last pair of opposite buds. One photo shows the Y-shaped branching pattern that results from the growth of the lateral buds in spring.


















Some Winter ID Guides

The following guides can help with winter ID of trees and shrubs. When using any guide or key, look at several twigs and buds to see what’s typical. Variations are common.

The LEAF Program from UW-Stevens Point is a K-12 forestry education initiative that offers many online resources. Under Curriculum & Resources, choose LEAF Tree Identification Tools. The LEAF Winter Tree ID Key is available there as a downloadable PDF.

Pocket Reference for Winter Tree Identification. Champaign County Forest Preserves, Mahomet, IL.

Fruit and Twig Key to Trees and Shrubs, by William M. Harlow, PhD. Reprint edition, 1959. Dover Publications, Inc., New York. ISBN 0-486-20511-8. 


Monday, December 19, 2022

Winter Identification of Deciduous Trees and Shrubs

Several ironwood trees with brown leaves in a snowy understory.


In winter, trees and shrubs can be identified using twigs, bark, overwintering fruit and sometimes leaves. This post offers some tips and terms for winter ID. A printable version is available for free through the Downloads tab.  


Tip #1: If they're within reach, look at twigs. 


A twig of green ash showing nodes, brown, blunt buds, and pale, semicircular leaf scars.











As in this photograph of Green Ash (Fraxinus pennsylvanica), look for the size, color, shape and texture of terminal, or end, buds and lateral, or side, buds (b). Lateral buds are attached at nodes (a) and are arranged in one of four patterns:
  • Alternate: One bud per node   
  • Opposite: Paired, or two buds per node
  • Subopposite: Paired but not quite opposite
  • Whorled: Three buds per node
Green Ash has opposite buds (d). 

The size and shape of leaf scars (c) can also help identify a species. These scars are left by petioles, or leaf stalks, when they fall from the tree. Green Ash typically has light, semicircular leaf scars.

    

Tip #2: Within leaf scars, look for vascular bundle scars.


These scars are made when strands of water- and food-conducting cells are severed in fall. Their size, number and arrangement are typical for a species. Some are easier to see with a magnifying lens. 

A series of three photos showing the vascular bundle scars of green ash, red elderberry and Catalpa.


Above left: Green Ash bundle scars are small, brown dots arranged in a semicircle.
Center: The bundle scars of Red Elderberry (Sambucus racemosa) are raised, irregular shapes arranged at the points and along the sides of a triangular leaf scar. 
Right: The bundle scars of Northern Catalpa (Catalpa speciosa) are light brown dots arranged in an oval.


Tip #3: Look at bark. 

Bark color and texture are helpful clues but can change with age. Also look for lenticels, spots or irregular shapes on the bark of younger trees or shrubs. In the photographs of Green Ash below, lenticels are the white spots on the reddish-brown bark of the sapling shown on the left (arrows).

On the right is a mature Green Ash showing the typical honeycomb-like pattern of ridges and furrows of its bark.

Two photos showing the reddish-brown, speckled bark of a green ash sapling and the gray, honeycombed bark of a mature tree.


Tip #4: Look for overwintering fruit.

Some species retain their fruits, or parts of them, well into winter. Also look under the shrub or tree for fruits that may be on the ground or on top of the snow.

A panel of four photos showing the overwintering fruits of winged burning bush, box elder, Kentucky coffee tree, and Amur cork tree.

Clockwise from top left: Red capsule walls of Winged Burning Bush, Euonymus alatus; samaras of Box Elder, Acer negundo; pods of Kentucky Coffee Tree, Gymnocladus dioicus, each 3 to 4 inches (7-10 cm) long; and the fruits of Amur Cork Tree, Phellodendron amurense


Tip #5: A few species hold on to their leaves.

Some trees are marcescent -- their leaves turn brown but aren't shed in fall. In this region, oaks (Quercus), Ironwood (Ostrya virginiana) and Blue Beech (Carpinus caroliniana) are among the few trees that are marcescent. 

Below is Ironwood, an understory tree that retains its leaves through winter. 

Ironwood trees with brown leaves in a snowy understory.









Tip #6: Remember MAD Cap Buck Horse.

Bud arrangement -- alternate, opposite, subopposite or whorled -- can quickly narrow choices for identification. One way to remember which species have an opposite arrangement is the mnemonic MAD Cap Buck Horse:

M            Maples (Acer)

A            Ash (Fraxinus)

D            Dogwoods (Cornus, except for alternate-leaved dogwood, C. alternifolia)

Cap        Plants that are or were in the family Caprifoliaceae, including honeysuckles (Lonicera), wolfberry or snowberry (Symphoricarpos), elderberry (Sambucus) and viburnums (Viburnum). 

Buck Horse    Ohio Buckeye (Aesculus glabra) and Horse Chestnut (Aesculus hippocastanum)


Although this mnemonic is helpful, it doesn't include all trees and shrubs with opposite buds. For example, Wahoo and Burning Bush, genus Euonymus, also have opposite buds. So does Bladdernut, Staphylea trifolia, an understory shrub.

Most remaining species have alternate buds. Common Buckthorn, Rhamnus cathartica, is unusual in having subopposite buds. Catalpa, another unusual species, has whorled buds. 


Tip #7: Look at the pith.

The pith is the center of a branchlet or twig. The appearance of the pith -- hollow or solid, color, texture -- can help confirm the identity of a tree or shrub. For example, honeysuckle shrubs (Lonicera, left photo below) have hollow piths, and Red Elderberry (Sambucus racemosa, right photo below) has a soft, yellow pith.

Two photos showing the cut twigs of honeysuckle and red elderberry.






Tip #8: Try these guides.

The LEAF Program from UW-Stevens Point is a K-12 forestry education initiative that offers many online resources. Under Curriculum & Resources, choose LEAF Tree Identification Tools. The LEAF Winter Tree ID Key is available there as a downloadable PDF.

Pocket Reference for Winter Tree Identification. Champaign County Forest Preserves, Mahomet, IL.

Fruit and Twig Key to Trees and Shrubs, by William M. Harlow, PhD. Reprint edition, 1959. Dover Publications, Inc., New York. ISBN 0-486-20511-8. 


Monday, December 5, 2022

Progress in Buckthorn Management

Seedlings of Common Buckthorn rise from the seedbank after an area is cleared of larger plants. Suppressing reinvasion
is a major challenge of Buckthorn management. 












Researchers at the University of Minnesota rank Buckthorn high on their list of problem invaders. They’ve been studying Common Buckthorn, Rhamnus cathartica, and Glossy Buckthorn, Frangula alnus, for years, and last summer they shared some of their findings.

Their white paper, Managing Invasive Buckthorn, focuses on two areas of research: goat browsing to manage Buckthorn growth and native plant cover to suppress reinvasion. Here are highlights from their work.


Goat Browsing Has Potential – and Pitfalls

On steep hillsides or other inaccessible places, goats are an alternative for removing buckthorn. Their browsing and trampling can reduce Buckhorn abundance and open the canopy, allowing more light to reach other plants.

Goats are most effective on small Buckthorn within the animals’ reach. To limit damage to other plants, fall is the best time to release the animals, but that’s also when they’re most at risk of acquiring meningeal worms. These brain parasites can infest snails and slugs that the goats also consume while browsing. Co-grazing ducks and geese with goats can lessen the risk, as waterfowl can eat infested snails and reduce their numbers but not get sick.  

Goats don’t eat just Buckthorn; they’ll eat other plants, too, including desirable ones. Some plants may rebound the following year, but they’ll be competing with Buckthorn that also resurges under the newly opened canopy. As explained in the next section, that’s why establishing cover is important after Buckthorn is removed, whether by goats or other means. A good way to suppress Buckthorn’s return, the researchers found, is to increase competition.

Part of this Buckthorn thicket was cleared with a forestry mower. Just a few 
years later, it has regrown to become as dense as the unmowed portion.









Native Cover Suppresses Reinvasion and Rebuilds Communities

Buckthorn management doesn’t end when the plants are cleared from an area. Reinvasion and a return to dominance are common, because Buckthorn can regrow from the seed bank or from cut stumps that weren’t treated with herbicide.

Fortunately, the researchers discovered a way to suppress reinvasion. They experimented with dense plantings or seedings of trees, shrubs, grasses and forbs and found that if light availability under plant cover drops below 3-4%, Buckthorn regrowth is limited. In closed forests with less light, planted trees and shrubs worked best to establish that cover. In more open areas, such as oak woods, both planted stock and seeded grasses and wildflowers were effective. The scientists are now experimenting with less dense planting and seeding.

Even after plant cover is introduced, it is important to monitor a site for germinating or sprouting Buckthorn.  As the native planting matures and casts more shade, removing Buckthorn should become easier as fewer plants survive. It’s a years-long effort, but with the right combination of techniques, Buckthorn should recede as the native plant community returns.

More Resources

For help identifying Buckthorn in winter, see this updated post from January 2021 or download this free, two-page guide. Additional Buckthorn information is available from the Minnesota Department of Natural Resources and the Minnesota Department of Agriculture.


Reference

Bernhardt, C., et al. 2022. Managing Invasive Buckthorn. University of Minnesota College of Food, Agricultural and Natural Resource Sciences and the Minnesota Invasive Terrestrial Plants and Pests Center.  CFANS-Buckthorn-White-Paper-June-2022.pdf (umn.edu)




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, Bugwood.org. 









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.

References

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 (bugwoodcloud.org)]

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. https://doi.org/10.3390/plants10102152.

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


References

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 (bugwoodcloud.org)]

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 https://doi.org/10.7717/peerj.5246

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 https://bugwoodcloud.org/resource/pdf/Biology_&_Biological_Control_Series/FHTET-2017-03_Biological_Control_of_Knotweeds_508.pdf.]

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 https://doi.org/10.7717/peerj.11783

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 (bugwoodcloud.org)]


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 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5699097/.

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.  https://doi.org/10.1111/nph.13288.

What Is a False Terminal Bud?

On trees and shrubs, a false terminal bud is a lateral bud at the end of a twig. Unlike a true terminal bud, it doesn’t enclose the growth a...