From the Lady Slipper Archives: Sweet Fern

The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. This is one of a series of reprints from past issues. This article, about sweet fern (Comptonia peregrina), first appeared in Vol. 26, No 1, Spring 2011. If you would like to see other past issues, visit the Lady Slipper Archives, where all issues from Vol. 1, No. 1, February 1986 to Vol. 35, 2020.

Sweet fern—A rare Kentucky shrub with an interesting history

By Tara Littlefield, Botanist, Kentucky State Nature Preserves Commission

Comptonia peregrine
Comptonia peregrine, KSNPC file photo

The wax myrtle or bayberry family (Myricaceae) is known for its odor. These plants have resinous dots on their leaves, making their leaves aromatic. Plants in this family have a wide distribution, including Africa, Asia, Europe, North America and South America, missing only from Australasia. Myricaceae members are mostly shrubs to small trees and often grow in xeric or swampy acidic soils. More familiar members of the wax myrtle family include many in the Genus Myrica (sweet gale, wax myrtle), some of which are used as ornamentals and are economically important. In addition, the wax coating on the fruit of several species of Myrica, has been used traditionally to make candles.

So what does this interesting family have in common with Kentucky’s flora? We are lucky to have just one species in the wax myrtle family, Sweet fern (Comptonia peregrina). In addition, it is also a monotypic genus restricted to eastern North America. This means that the genus Comptonia has only one species (C. peregrina) worldwide, and just happens to be found here in KY! Of course the common name sweet fern is misleading. This woody shrub is certainly not a fern. However, the leaves have a similar shape to pinnules of a fern frond (leaf). But having sweet in the common name is no mistake. If you crush the leaves throughout the growing season, a lovely smell is emitted as the essential oils volatilize into the air.

Female flowers (short round catkins with reddish bracts) and male flowers (elongated catkins clustered at the branch tips) – www.nativehaunts.comphenology.html

Sweet fern is a clonal shrub that grows up to one meter high and spreads through rhizomes. The leaves are alternate and simple, linear and coarsely irregularly toothed, dark green above and a bit paler below. It is monoecious (meaning male and female flowers on different plants). The female flowers are not showy— short rounded catkins [dense cluster of apetalous flowers, usually associated with oaks, birches and willows] with reddish bracts. The male flowers are elongated yellow-green catkins clustered at the branch tips, the pollen being adapted to wind dispersal. The fruit is a round, bur-like cluster of ovoid nutlets that turn brown when mature in late summer. The bark is reddish and highly lenticeled (small corky pores or narrow lines on the bark that allow for gas exchange).

While very common in the northern part of its range (northeastern United States and Canada), sweet fern is state listed endangered in Kentucky, along with being state listed as rare inOhio, Tennessee, South Carolina, West Virginia, Georgia, and North Carolina. The populations of sweet fern in the southern part of its range are isolated and disjunct from the common habitats up north. There seems to be a close association of these remnant populations with the Appalachian Mountains, which suggests that the populations in the southern ranges remained in protected “refugia” during periods of great plant migrations, such as during glaciations.

Sweet fern is typically found in openings in coniferous forests with well drained dry, acidic sandy or gravely soils with periodic disturbances. In the north, it can be found in pine-oak barrens or jack pine and spruce forests that are maintained by fire, creating openings and decreasing competition. It has also been noted to colonize road banks and even highly disturbed soils such as mined areas. Contrary to these open coniferous habitats with periodic fire, the remnant populations of sweet fern in Kentucky and Tennessee are found on sandstone cobble bars, which are maintained by annual floods. Despite being found on habitats that are maintained by different disturbance regimes, these two communities share a few things in common—they are both dry, acidic, sandy and nutrient poor. Disturbances are a natural occurring impact in these communities that removes shrubs and saplings, thus decreasing competition so that sweet fern can thrive.

Sweet fern has adapted to these specialized habitats. It is a fires adapted species; it will resprout after a fire and increase its clonal sprouts through underground rhizomes. It is also a xerophyte, a plant adapted to dry conditions. And since it is adapted to living in nutrient poor, acidic soils, it has evolved with the bacteria Frankia that fixes nitrogen, somewhat like the more famous nitrogen fixing legumes who have partnered with the bacteria Rhizobium. Did you know that there are over 160 species of nonleguminous plants that fix nitrogen? It is also the host of the sweet fern blister rust (Cronartium comptoniae) which reduces the growth of pines, particularly Jack pine. What interesting relationships this shrub has with bacteria and fungi! In addition, sweet fern is the food plant to larvae of many species of Lepidoptera (moths and butterflies). These include the Io moth (Automeris io), and several Coleophora case-bearers (some of which are found exclusively on sweet fern).

But perhaps the most fascinating facts about the rare shrub sweet fern is what it can tell us about the evolution of plants, the history of the earth, and the paleovegetational past of Kentucky. Geologically speaking, sweet fern is an old plant. In Kentucky, it was most likely more common some 20,000 years ago during the last glaciation, as Kentucky used to look like Canada. Analysis of pollen in sediment cores taken from natural ponds in Kentucky confirms this, spruce and jack pine was common in the uplands in the bluegrass. Sometimes it is difficult to think of plants migrating north and south in order to adapt to a changing climate. But what is even more mind blowing is that the genus Comptonia is perhaps millions of years old. Numerous fossils of dozens of extinct species of Comptonia have been found all across the Northern hemisphere, and the earliest of the fossils have been dated back to the Cretaceous period (the age of the Dinosaurs) over 65 million years ago. The first flowering plants (angiosperms) evolved only 135 million years ago, so Comptonia is one of the oldest living plants in the world—a true living fossil!

So when April comes around, and all of the spring wildflowers are emerging, think of sweet fern tucked deep into the gorges of Big South Fork and Rockcastle, its catkins releasing pollen in the wind, using the nitrogen fixed from its bacterial friends, withstanding the massive floods of two of Kentucky’s last wild rivers. And if you use your imagination, you may be able to see dinosaurs and tree ferns in the distance.

  1. Berry, Edward W. 1906. Living and Fossil Species of Comptonia. The American Naturalist. Vol. 40, No. 475, pp. 485-524.
  2. Darlington, Emlen. 1948. Notes on some North American Lepidoptera reared on Sweet Fern (Compontia asplenifolia Linnaeus) with Description of new species. Transactions of the American Entomological Society (1890-). Vol. 74, No. 3, pp. 173-185.
  3. Liag, X., Wilde, V., Ferguon, D., Kvacek, Z, Ablaev, A., Wang, Y., and Li, C. 2010. Comptonia naumannii (Myricaceae) from the early Miocene of Weichang, China, and the paleobiogeographical implication of the genus. Review of Paleobotany and Palynology. Vol. 163, p. 52-63.
  4. Medley, Max and Eugene Wofford. 1980. Thuja occidentalis L. and other noteworthy collections from the Big South Fork of the Cumberland River in McCreary County, Kentucky. Castanea. Vol. 45, No. 3, pp. 213-215.
  5. Natureserve Explorer, 2010.
    https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.134920/Comptonia_peregrina
  6. Wilkins, Gary, Delcourt, Paul, Delcourt, Hazel, Harrison, Frederick, and Turner, Manson. 1991. Paleoecology of central Kentucky sicne the last glacial maximum. Quaternary Research. Vol. 36, Issue 2.
  7. Virginia Tech Woody Database
    http://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=869
  8. Zomlefer, W. 1994. Guide to Flowering Plant Families. University of NC Press, Chapel Hill.

From the Lady Slipper Archive: Kentucky’s ‘Tropical’ Fruit, the Pawpaw

The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. This is one of a series of reprints from past issues. This article, about North America’s largest native fruit, the pawpaw (Asimina triloba), found in every county of KY, first appeared in the fall of 2005, Vol. 20, No. 3. If you would like to see other past issues, visit the Lady Slipper Archives, where all issues from Vol. 1, No. 1, February 1986 to Vol. 34, No. 1, Winter/Spring 2019 (after which we moved to this blog format) can be found.

The author, John Thieret, left a huge legacy to the native plant community when he passed in 2005. “Kentucky has lost its most renowned American plant taxonomist of the 20th century. John W. Thieret, Professor Emeritus of Biological Sciences at Northern Kentucky University, retired Director of the Northern Kentucky University Herbarium, Associate Editor of Sida, Contributions to Botany, and Editor of the Journal of the Kentucky Academy of Science (JKAS) passed away on 7 December 2005, at Alexandria, Kentucky.”

To learn more about this giant of Kentucky Botany, read the articles and tributes to him in the Winter 2005/Spring 2006, Vol. 20, No. 1, of the Lady Slipper archives.

Kentucky’s ‘Tropical’ Fruit,
the Papaw

by John Thieret, NKU

pawpaw fruits
Photo: Ellwood J.Carr, from the collection
of the Pine Mountain Settlement School

A visit to a fruit/ vegetable market in the tropics is a great experience. All sorts of plant products that we in the temperate zones do not recognize are there. Among these are fruits of the Annonaceae, the custard-apple family, including the bullock’s-heart, cherimoya, guanabana, sweetsop, and soursop. These are unknown to most people in our part of the world, but we do have a member of the Annonaceae that does NOT grow in the tropics, our papaw, Asimina triloba. This is a shrub or small tree, which, as I have seen it, never exceeds perhaps 20 feet in height and 6 inches in trunk diameter, although there are reports of individuals 50 feet tall and with a trunk 2 feet in diameter, truly a mega-papaw.

A common enough plant, the papaw thrives in rich woods over much of eastern U.S. from northern Florida to far eastern Texas, then north to New York, far southern Ontario, Michigan, Iowa, and southeastern Nebraska. It grows throughout Kentucky, almost certainly in every county.

Although some papaw enthusiasts wax ecstatic over the fruits, papaws are not everyone’s favorite. This divergence in appreciation stems from, first, natural differences in fruits from different trees and, second, differences in people’s taste buds. I have found fruits from some trees not worth the effort of trying to get them down from the branches. But other trees can produce fruits that I’d describe as almost excellent. The best papaws I ever tasted were in southern Illinois on a rather cool, almost frosty fall morning. Yes, quite worthwhile. The Indiana poet James Whitcomb Riley described, in hoosier dialect, the gustatory experience:

And sich pop-paws! Lumps a’ raw
Gold and green,—jes’ oozy th’ough
With ripe yaller—like you’ve saw
Custard-pie with no crust to.

Another assessment of the taste, by an Indiana lad, is included in Euell Gibbons’ book Stalking the Wild Asparagus: “They taste like mixed bananers and pears, and feel like sweet pertaters in your mouth.” I’ll second that, at least for a good papaw.

Long before Europeans began their assault on the North American continent,the indigenous peoples, along with various animals—possums, raccoons, squirrels, and skunks—sought the fruit. The first Europeans to see it—some 450 years ago—were De Soto and his entourage. They wrote of it, mentioning its “very good smell and excellent taste.” About 200 years later the plant was introduced into cultivation by Europeans who brought seeds to England. Then in1754 the first illustration of the papaw appeared in Catesby’s Natural History of Carolinas (see right). Lewis and Clark, in the early 19thcentury, found the fruits to be welcome additions to a meagre diet. To this day, the fruits are collected and used by country people and by city dwellers who like to eat their way through the landscape.

As for ways to use the fruits, first and foremost they can be eaten out of hand. As they ripen, they change from green to brown or nearly black, then looking not especially appetizing (recalling ripe plantains). The fruit pulp, creamy and sweet, contains several large,flattened, brown seeds. One of my friends made a necklace for his wife from the seeds. Better, I guess,than one made from finger bones.

Enthusiasts use the fruit for pies, puddings,marmalade, bread, beer, and brandy. I’ve tasted papaw bread and found it OK. Barely. I once tried to make papaw bread—I’ll say no more about that dismal experience. (The persimmon bread I attempted was no better.)

On a few occasions I have seen the plant grown as an ornamental. With its large, somewhat drooping leaves, it is rather attractive. The maroon flowers,which bloom in spring when the leaves are still young and covered with rusty down, are not all that conspicuous, and the fruits—well, my experience has been that papaw plants in cultivation as lawn specimens just do not make many fruits. As a matter of a fact, I have always noted that, even in the wild,the fruits are not abundantly produced. Maybe I just was not at the right place at the right time. The plants seem to require cross pollination, which is a disadvantage to those who would use them as ornamentals and, at the same time, would like some fruits.

If you have never tried one of the fruits, head for the woods in the autumn and attempt to find one. Maybe someone you know can help you. Even if you do not find the fruit much to your liking—maybe you will,maybe you won’t—you will have had a new gustatory experience.

For many years attempts have been made by horticulturists to ‘improve’ the papaw and make it into a commercially viable fruit. Their efforts notwithstanding, the fruit remains a Cinderella. On only one occasion have I seen papaws for sale: at a roadside farmer’s stand in southwestern Ohio among a fine display of squashes of a dozen kinds. Breeding and selection work has been carried out in several places, notably at Kentucky State University where about 1700 papaw trees grow in KSU’s 8-acre experimental farm and where the PawPaw Foundation is headquartered. Once, in Pennsylvania, I saw a papaw orchard of maybe 50 trees. I wish now that I had stopped and spoken with the orchard’s owner.Perhaps, with continued efforts at breeding and selection, papaws might some day be common items in our temperate fruit and vegetable markets, as common even as are the annonaceous cousins of Asimina triloba in markets of the tropics. This is the goal toward which papaw enthusiasts and breeders are striving.

From the Lady Slipper Archive: 2005 Wildflower of the Year, SHOWY GOLDENROD (Solidago speciosa)

The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. This is one of a series of reprints from past issues. This article, about one of Kentucky’s loveliest goldenrods, first appeared in the spring of 2005, Vol. 20, No. 1. If you would like to see other past issues, visit the Lady Slipper Archives, where all issues from Vol. 1, No. 1, February 1986 to Vol. 34, No. 1, Winter/Spring 2019 (after which we moved to this blog format) can be found.

The author, Mary Carol Cooper, left a huge legacy to the native plant community when she passed in 2016. In almost every native plant gathering, her name is mentioned and a moment is given over to appreciate her knowledge, which she freely shared. Her passion led many of us to our love of natives; she was a mentor and friend to many of us.

2005 Wildflower of the Year
SHOWY GOLDENROD (Solidago speciosa)

By Mary Carol Cooper
Salato Native Plant Program Coordinator
Salato Wildlife Education Center

Showy goldenrod (Solidago speciosa)
Photo by Tom Barnes

Wildflower enthusiasts from all across the state have selected Showy Goldenrod (Solidago speciosa) as the Salato Native Plant Program’s Wildflower of the Year for 2005. The Wildflower of the Year is chosen based on the number of nominations it receives and how well it fits the established criteria; must be native to Kentucky, common and widespread across the state, seeds must be readily available, must be easy to grow, and must have good wildlife value.

Showy Goldenrod is a hardy perennial that grows 2 to 6 feet tall, depending on where it is planted. It is a rather showy species with stout, smooth, reddish stems and smooth, deep green leaves that are 4 to 10 inches and not toothed. It grows in rich thickets, woodland openings, fields, and prairies. It likes average to well drained soil and grows in sun to partial sun. It has dense upright pyramidal flower clusters. Each flower head has 6 to 8 rays. Showy Goldenrod blooms in late in the summer (August to September) and is wonderful as a late summer nectaring source for bees, butterflies and hummingbirds. It also provides food for several species of songbirds such as the Goldfinch, Junco, Pine Siskin, Song and Tree Sparrows.

Goldenrods are insect pollinated and their pollen is heavy and sticky. Therefore their pollen is never in the wind, so contrary to popular belief, this is not the plant that has always been blamed for causing hay fever. It is ragweed that causes all the misery! Ragweed blooms at the same time and is wind pollinated. I’ve enjoyed watching more and more floral designers use goldenrods in their arrangements and wonder how many people are aware that their lovely bouquet is full of the “dreaded goldenrod”.

Goldenrod is truly a North American flower. There are approximately 125 species in North America and more than 30 of these are native to Kentucky. Since the State Flower is Solidago ssp. this must mean that we have 30 State Flowers! Two of out native goldenrods, White-Haired Goldenrod and Short’s Goldenrod are on the Federally endangered species list.

Showy Goldenrod makes a nice background or midground plant in a sunny perennial garden. Establish this plant at the very rear of the garden or in the very middle of a circular or oval garden. Allow 3 feet between plants as this species grows into large clumps very fast. They can be divided every year or so and given to friends and neighbors. Nice companion plants are Ironweed, Great Blue Lobelia and New England Aster. Plants naturalize quickly on dry sunny banks. The cuttings are outstanding in arrangements.

The genus name Solidago comes from the Latin word that means “to make whole” or “to heal”, a name chosen because of medicinal power the plant was believed to have. The Native Americans used this plant for many things including ridding people from pain and evil spirits. One Goldenrod superstition says that he who carries the plant will find treasure, therefore, Goldenrod is the symbol for treasure and good fortune.

Goldenrod seeds and plants are available from many native plant nurseries. It is also very easy to propagate either by seeds, or division. Sow seeds thickly in outdoor seedbeds early in the fall or sow stored seed later in a flat indoors or in a cold frame. Transplant when there are 3 to 4 leaves. When the roots fill the pot, transplant in the garden after the last frost date. Collect seeds in late September or October. Cut off seed heads and put them upside down in a large paper bag. Let them dry for up to a week and then shake them in the bag and put the seeds in a sealed container.


Citizen science opportunity: have you seen falcata alfalfa?

By Jonathan O.C. Kubesch, University of Tennessee—Knoxville

Falcata alfalfa (Medicago sativa ssp falcata) is a stunning subspecies of the purple-flowered alfalfa commonly seen in the eastern United States (Figure 1; USDA-NRCS Plant Materials Program, 2015). Falcata alfalfa was introduced to South Dakota from Siberia by an eager professor in the early 19th century, however, the subspecies has appeared in the Kentucky flora in the time since (Shaw et al., 2020; Smith 1997). Falcata alfalfa improves the quantity and quality of forages for rangeland with tradeoffs for native species richness in South Dakota (Xu et al., 2004). The Kentucky collections may have come in seed bagged from elsewhere, especially as seed production shifted from the region to the Willamette Valley of Oregon (Figure 2).



Figure 1. Falcata alfalfa. Courtesy of Bing Creative Commons (accessed August 19, 2020).

Falcata alfalfa’s use in rangelands presents a question: why alfalfa has not naturalized into the South? Given it has historically been found in cultivated and disturbed environments, has the species formed any stable populations outside of agricultural use? And given falcata’s success in the High Plains, why hasn’t the species been used in the South?

Figure 2. The Willamette Valley of Oregon. July 10, 2020.
Figure 3. Falcata alfalfa (USDA PI 631577) growing on a misting bench in Knoxville, Tennessee. August 19, 2020.

Falcata is promising given its performance in low fertility conditions (USDA-NRCS Plant Materials Program, 2015). A research project at the University of Tennessee is investigating the horticultural performance of falcata alfalfa in the Southeast. Seed from the United States Department of Agriculture—by way of Canada and originally from eastern Italy—is being grown to study the plant in the eastern United States (Figure 3; USDA PI 631577). Concerns about introducing new plant species into the Southeastern flora prompted this present article. A fair number of plants introduced to the eastern United States have gradually moved outside of agricultural fields, such as tall fescue (Schedonorus arundinaceus), but the subspecies of alfalfa have not escaped and persisted for extended periods in the wild. 

The Tennessee-Kentucky Plant Atlas is a helpful tool for this sort of research (Shaw et al., 2020). Documenting the localities and conditions that falcata alfalfa has been found in the native flora should expound on these questions and theories regarding the species and subspecies persistence in the Southeast. Through the Atlas we can tell that escaped alfalfa does not necessarily take over native habitat in Kentucky and Tennessee in the same way that alfalfa has persisted in the High Plains of South Dakota. However, the Atlas is limited to collections made before 2002 (Shaw et al., 2020). With that in mind, citizen scientists are critical to documenting falcata alfalfa in Kentucky in 2020. The species should be seen where the purple flowered alfalfa occurs, such as disturbed areas and pastures.

Continue reading Citizen science opportunity: have you seen falcata alfalfa? →

From The Lady Slipper Archives: New England Aster: 2010 Wildflower of the Year

The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. With this article, we will begin to occasionally feature an article from a past issue. This one, about one of Kentucky’s loveliest natives, the New England Aster, first appeared in the summer of 2010, Vol. 25, No. 2. If you would like to see other past issues, visit the Lady Slipper Archives, where all issues from Vol. 1, No. 1, February 1986 to Vol. 34, No. 1, Winter/Spring 2019 (after which we moved to this blog format) can be found.

The author, Mary Carol Cooper, left a huge legacy to the native plant community when she passed in 2016. In almost every native plant gathering, her name is mentioned and a moment is given over to appreciate her knowledge, which she freely shared. Her passion led many of us to our love of natives; she was a mentor and friend to many of us.

New England Aster: 2010 Wildflower of the Year

By Mary Carol Cooper, Salato Center Native Plant Program Coordinator

The Wildflower of the Year is chosen based on the number of nominations it receives and this year more wildflower enthusiasts statewide voted than ever before! They chose New England Aster (Symphyotrichum novae-angliae) as the Salato Native Plant Program Wildflower of the Year for 2010. Aster comes from the Greek word for “star.” It describes the star-like form of the flower. Other familiar words using “aster” are astronomy, astrology and astronaut. According to Greek legend, the aster was created out of stardust when Virgo (the maiden Astraea, goddess of innocence and purity) looking down from heaven, wept. Asters were scared to all the gods and goddesses and beautiful wreaths made from the blossoms were placed on temple altars on very important festive occasions. Known in France as “eye of Christ” and in Germany as starworts, asters were often burned to keep away evil spirits. A hodgepodge of asters was thought to cure the bite of a mad dog. Shakers used the plant to clear their complexions and ancient Greeks used it as an antidote for snakebites and to drive away snakes. Virgil believed that boiling aster leaves in wine and placing them close to a hive of bees would improve the honey. Native Americans found many uses for asters, from treating skin rashes and earaches to stomach pains and intestinal fevers. Nerve medicines and cures for insanity were made from some asters and others were eaten as food. Some were smoked in pipes as a charm to attract game, especially deer. Today there are no medical uses for asters.

New England Aster, photo by Thomas Barnes

The genus Aster has recently undergone a name change due to close study using DNA testing and other techniques. There are about 150 flowering plants in North America traditionally placed in the aster genus. About 50 of them are considered common and widespread. Now there is only one species left with the name Aster. The other species have been given several tongue-twisting generic names. For the botanist, renaming of the asters brought accuracy and order. For the layperson, it removed some wonderfully colorful names and replaced them with unspellable and unpronounceable names! Aster novae-angliae was translated as “star of New England” and now as Symphyotrichum novae-angliae, it is literally “fused hairs of New England.” The word Symphyotrichum was created in 1832 to describe the hairs on the seeds of a European plant.

New England Aster is an erect perennial that grows to a height of 2’ to 6’ tall with a stout root crown or thick, short rhizome and clustered stems, usually with spreading hairs. The leaves are alternate, sessile, entire, lanceolate, 1” to 4” long with pointed lobes at the base that conspicuously clasp the stem. The ray flowers range from violet, rose, or magenta and are very showy. The disk flowers are yellow. This aster is one of our largest and showiest asters. There can be from 40 to 80 ray flowers on a head! These asters bloom from August to October and are a critical late-season nectar plant for butterflies, especially the Monarch, that stock up for their long migration to Mexico. New England Asters are found in mesic to wet open woods and fields across Kentucky. They prefer average to moist soil and full sun. Not only are the New England Asters critical for Monarch butterflies, it is the host plant for the Pearl Crescent and one of the host plants for the Saddleback Caterpillar Moth. Several game birds, including the wild turkey, a few songbirds, including the tree sparrow, and small mammals, such as the chipmunk and white-footed mouse, feed on the leaves and seeds. Work plantings of New England Aster into your fall landscape. Use them singly or in small groups in the rear of a sunny border. They look beautiful with our native sunflowers, goldenrods, mistflower and rose mallow. They are also perfect for rain gardens as they thrive on moist to dry soil. They are easy to naturalize in roadside ditches, road banks, and open grassy areas. A sunny site where soil remains moist throughout the season is also ideal. Asters have always been recognized as decorations. The flowers of most species last several days after being picked and put into vases, so what better than New England Asters in beautiful fall arrangements along with other fall bloomers.

Ecological Effects of Amur Honeysuckle Infestations

By David D. Taylor

This article expands on Invasive Plant Corner – Bush Honeysuckle (Lonicera Spp.), in the April 2020 issue.

Amur honeysuckle (Lonicera maackii) is the most widespread and arguably the most invasive of the nonnative invasive honeysuckle shrubs in Kentucky. Jeff Nelson’s article on Amur honeysuckle provides a general overview of the species. This article provides some details as to why this species is so invasive and why is an ecologically undesirable species.

Amur honeysuckle, native to central and northeastern China, Japan (rare), Korea, and far eastern Russia, occurs as an understory shrub in open hardwood and mixed hardwood-conifer forest consisting of oaks, elms and other hardwoods and fir, spruce and hemlock. It is also known from and more common in riparian and scrub communities (Luken and Thieret 1996). It grows as scattered individual shrubs or small clumps, not unlike viburnums do in Kentucky. Large, dense stands do not typically occur, but in open, riparian areas it can be weedy. In its native range, individuals typically do not exceed 4 inches diameter and 20 feet tall (Yang et al. 2011). In Kentucky, the species is often an understory shrub in open forest, but forms dense thickets at forest edge, along fence rows and in open areas. It grows larger here as well, to 6 inches diameter and 30 feet tall (personal observation).

Large Amur honeysuckle, two stems 5 inches or greater in diameter.
29 April 2020. 
Photo by David Taylor

This shrub leaves out early in spring, often breaking bud in mid-March, long before native trees and shrubs. By mid-April of most years, leaves are fully expanded, and the shrubs are actively growing. In the fall, Amur honeysuckle typically senesces (leaves turn yellow and drop) in late October to mid-November, and sometimes not until early December. Native trees and shrubs typically break bud late March to mid-April and do not fully expand until early May. In eastern Kentucky, they are actively dropping their leaves by mid- to late October in most years. The extra 5-8 weeks of photosynthetic activity in the honeysuckle allows it to store additional energy giving it an edge over native species (McEwan et al. 2009). It is also somewhat tolerant of late freezes. Both promote its invasive nature.

Tall Amur honeysuckle, approximately 27 feet tall. 
29 April 2020. 
Photo by David Taylor

While Amur honeysuckle grows better in full sun (Luken 1995), it is known to survive in 1 percent of full sunlight in the heavy shade of trees (Luken et al. 1997a). The native spring flowering spice bush (Lindera benzoin) by comparison, requires about 25 % of full sun to survive (Luken et al. 1997a). Forest grown Amur honeysuckle under heavy shade tends to produce few stems which grow upward toward light specks. They tend not to have much branching, nor do they attain much diameter. In the open, individual shrubs produce numerous stems and branching is extensive. Maximum diameters are obtained in the open (Luken et al 1995a). Overtopped Amur honeysuckle shrubs respond with the production of long, upright stems that seek light. Honeysuckle in open forest may branch extensively and produce heavy shade.

Continue reading Ecological Effects of Amur Honeysuckle Infestations →

Native clover conservation in the Bluegrass: an agronomic perspective

Jonathan O.C. Kubesch, University of Tennessee

Clovers are an odd group of plants caught between agriculture and agronomy, especially in the Bluegrass. Agronomists and cattlemen find clovers important for their nitrogen contribution and nutritive value to livestock. Horse owners fear clover for the fungal pathogen behind slobbers. Wildlife managers use them for food plots. Of the roadside clovers, most came to Kentucky with settlers (Ball et al., 2015; Bryson and DeFelice, 2009). Those red and white clovers came with the tall fescue and Kentucky bluegrass. These species play an important role in Kentucky agriculture; however, the horse parks and cattle farms have replaced the natural ecosystems in the state (Noss, 2013; Campbell, 2014; Campbell, 2010).

In addition to these introduced species, Kentucky has three prominent native clovers: annual buffalo clover, running buffalo clover, and Kentucky clover (Vincent, 2001). Although collections of the native clovers have been made across Kentucky, it is really very uncommon to find these populations unless one knows where someone else has previously found it. It is unlikely that the reader will find these species in the local park or native area.

Annual buffalo clover (Trifolium reflexum), is spread throughout most of the eastern United States. The beautiful blooms have led to its potential as a horticultural species (Quesenberry et al., 2003). Of the native clovers, the genetics of the flowering in annual buffalo clover have been the most explored: red, white, and pink flowers (Quesenberry et al., 2003). At one point, it was favored over naturalized white clover in unimproved grazing lands (Killebrew, 1898).

Running buffalo clover (Trifolium stoloniferum) is a perennial species limited to the Ohio River Valley and Missouri. Plants spread on thick runners like strawberries. The species was investigated as a potential forage in the 1990s, and has been the subject of interest for herbivory dynamics in the eastern United States. The thick seed coat requires scarification in order for the seed to germinate (Kubesch, 2018; Sustar, 2017). Hoof action has been proposed as a driver in the ecology of the species, but a general disturbance regime seems necessary for the species to persist in the landscape (Kubesch, 2018). With some sandpaper and a few hours of free time, seed can be scarified. Running buffalo clover grows readily in the greenhouse.

Running buffalo clover in the greenhouse. Photo credit: Jonathan Kubesch
Continue reading Native clover conservation in the Bluegrass: an agronomic perspective →