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.

Rediscover hedgerows

By Alicia Bosela, Owner of Ironweed Native Plant Nursery

Hedgerows—strips of mixed plants and shrubs—are a wonderful under-utilized and under-appreciated habitat. They have been called linear nature preserves in the sense that they can be highly diverse (combining meadow and forest plants), they support a wide array of wildlife, and they provide ecosystem functions that sustain the health of our air, land, and water. 

Hedrerow 2 -- Mindy Rose
Photo by Mindy Rose.
Cecropia Betty Hall
This Cecropia moth cocoon would be well protected in a hedgerow.
Photo by Betty Hall.

Their benefits to wildlife span the spectrum.  The woody species alone might read like a veritable critter buffet: hazelnut, wild plum, persimmon, red mulberry, wild crabapple, and elderberry.  Other food for wildlife includes both early nectar—blooming redbud, viburnum, dogwood, hawthorn, and black cherry—and late season nectar—asters, sunflowers, and goldenrods.  Hedgerows provide shelter for wildlife, a nesting place for birds and create corridors that allow safe passage for scores of species from salamanders to rabbits.  The leaf litter is a virtual nursery for developing stages of lightning bugs and other beneficial insects.  Many Lepidoptera (moths and butterflies) roll up in leaves to overwinter in the litter, snug as a bug! 

When we think of attracting wildlife like hummingbirds and butterflies to our yard, our first thought might be of a continuously flowering native pollinator garden.  While pollinator gardens are highly recommended and needed, we have learned from the monarch that a dearth of larval host plants might be a weak link in the chain of our pollinator’s lifecycle.  In general, woody plants host the caterpillar stage of more Lepidoptera than herbaceous plants.  More woody host plants mean more caterpillar food and more caterpillars to feed native birds and their young. 

From a management perspective, it is important that invasive exotics like autumn olive, Bradford pear, wintercreeper, bush honeysuckle, and privet be removed in favor of native plants.  A study by Dr. Tallamy, a University of Delaware entomologist and ecological gardening advocate concludes, “…in terms of the everyday needs of the animals that eat caterpillars, we found 96 percent less food available in the invaded (non-native hedgerow) habitats!” 

…native hedgerows are certainly a habitat worth rediscovering…

There are physical benefits of hedgerows as well. They catch and store water, act as windbreaks, and protect against erosion. In residential areas, they are great privacy fences, sound buffers, and can prevent snow drifts. A final benefit of native plant hedgerows is that they really ‘pay it forward’ when birds disperse seed from native plants instead of spreading seed from invasive exotics. Though under-utilized, native hedgerows are certainly a habitat worth rediscovering.

Hedgerow 1 Mindy ose
Hedgerows provide habitat and they’re beautiful–it’s a Win! Win!
Photo by Mindy Rose.

References: Nature’s Best Hope by D. Tallamy (2019).

Alicia Bosela owns Ironweed Native Plant Nursery in Columbia Kentucky, a certified woman-owned business. Before opening her own nursery, she was the Assistant Director of Clay Hill Memorial Forest Environmental Education Center. You can contact her at www.ironweednursery.com.

Ironweed Nursery logo

Book Review: The World of Clovers

By John M. Gillett and Norman L. Taylor, Michael Collins (Editor)

Reviewed by Jonathan O.C. Kubesch, University of Tennessee—Knoxville

Author’s Note: True clovers (Trifolium spp.) are the focus of this article. All scientific names abbreviate Trifolium to T.

The World of Clovers, by John M. Gillett and Norman L. Taylor (2001), is a fantastic primer on the global diversity of the genus Trifolium. Conceived in concert with a world seed collecting effort, Gillett and Taylor work to describe the many known species of this familiar genus. The global distribution of the genus is discussed and the book highlights origins for these species. Native clover species form intriguing distributions. This book covers details in morphological diversity beyond the traditional field guide using photographs. Notes cover the trivial and surprisingly nuanced characteristics of each species. In the 20 years following publication, some new information has developed about these species in the genus Trifolium. However, the book is a strong introduction for the botanist to explore a wider world of clovers.

This book is especially relevant to Kentucky botanists. Norman L. Taylor sought to collect every known species of clover and seed bank them in Lexington, KY. This work led to a framing of the genus (~230 species) with ever-expanding global coverage. Clovers are native to North and South America, Africa, Europe, and the Near East. Surprisingly, clovers are not native to Australia! The Great Plains and Coastal Plain have few native clovers, but the woodland-grassland mosaic of the Southeastern United States supports a handful of native species, such as the running buffalo (T. stoloniferum), Carolina (T. carolinianum), and running glade clovers (T. calcaricum) in addition to the introduced Eurasian species, such as red (T. pratense) and white clovers (T. repens).

The World of Clovers appeals across disciplines and levels. Gillett and Taylor seek to make the diagnostic information as accessible as possible, using common language to avoid a technical glossary. The description and photograph accompanying each species’ seed suits the conservation mission. The black-and-white images on the pages are complemented by an enclosed CD. Moving beyond the traditional field guide or agronomic factsheet, the book gives reproductive biology information. This reproduction section of each species entry suits efforts to propagate plants in cultivation or to encourage success in the wild. The number of cross-pollinated species draws additional attention to the plight of pollinators.

Clovers have served primarily as forages for wildlife and livestock. However, the horticultural benefits of these species also come to mind. The authors mention Kura clover and buffalo clover as two prominent candidates for their ornamental beauty. Of buffalo clover, as an extension of Norman Taylor’s personal fondness, Clovers says, “Many consider this species the most beautiful of the clovers….” In addition to the technical details, these small comments offer some humanity to the often impersonal business of plant sciences. New finds in the taxonomy of the clovers have led to the identification of a new species, Kentucky clover (T. kentuckiense), which is closely related to buffalo clover (T. reflexum)(Chapel and Vincent, 2013).

In 20 years of scientific and economic advancement the world of clovers has changed. Taylor passed in 2010, and his collection was split between Washington State and Georgia USDA seedbanks. Similarly, the use of clovers in agricultural settings has expanded to develop living mulch and perennial ground cover systems. Clovers will hopefully reduce the use of synthetic inputs in agricultural to the benefit of adjacent natural ecosystems.

Dr. Michael Vincent’s 2001 summary of Kentucky’s Trifolium, complements the World of Clovers in further detail on the 11 (now 12 due to the subsequent discovery of T. kentuckiense) species seen in Kentucky (Vincent, 2001). Clovers are part of the historical herbivory and current cropping of the state. This book is a limited description at the species level which the ecologist may apply in conjunction with similar guides on the KY flora.

The World of Clovers is useful to professional and citizen scientists because it encompasses the diversity of the genus. This book goes beyond the traditional field guide, but also comes in an accessible form for the everyday user. Clovers exist under cultivation as well as in Kentucky’s natural areas. The genus Trifolium has grown in a small degree in the time since publication, but the book offers wider coverage that serves both the hiker and horticulturalist.

Acknowledgements

Norman Taylor deserves special mention to his dedication in preserving the native clovers of Kentucky. This article is part of the ongoing efforts of the Kentucky Clover Recovery Team. Will Overbeck provided helpful suggestions and strong editorial contributions. Special thanks to David Barker, Daniel Boone, and Ken Quesenberry for recommending this book. Thanks to Sarah Grace Holland, for her supporting my native clover research.

References

Chapel, K. J., & Vincent, M. A. (2013). Trifolium kentuckiense (Fabaceae, Papilionoideae), a new species from Franklin and Woodford counties, Kentucky. Phytoneuron 2013-63: 1–6.Chapel and Vincent 2013.

Gillett, J. M., & Taylor, N. L. (2001). The World of Clovers. Ames, IA: Iowa State University Press.

Vincent, M.A. (2001). The genus Trifolium (Fabaceae) in Kentucky. J. Ky. Acad. Sci. 62(1):1-17.

Jonathan Omar Cole Kubesch is a graduate student pursuing a master’s degree in crop science at the University of Tennessee. He studied evolution and ecology—as well as agronomy—at the Ohio State University. He works on forages, grasslands, and prairies with a particular passion for native clovers.