The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. We occasionally feature an article from a past issue. This one, about Kentucky’s most widespread milkweed species, Common Milkweed (Asclepias syriaca), first appeared in the fall of 2011, Vol. 26, 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.

Kentucky’s Common Milkweed (Asclepias syriaca L.)
By David Taylor, US Forest Service

Common milkweed is a perennial forb that spreads by means of rhizomes and seed. It is one of about 115 species that occur in the Americas. Most species are tropical or arid land species. Plants may occur as a few individuals, but once established, form small to large colonies. Individual plants range from 1 to 2 m (~ 3 to 6 ft) tall. Leaves are elliptic to ovate to oblong and somewhat thick. Mature leaves are 15-20 cm (6-8 in) long and 5 to 9 cm (~ 2 to 3.6 in) wide, with a prominent midvein. The underside of the leaf is frequently finely pubescent. The stem is stout, usually simple, and green to black (see below) in color. When broken, the leaves, as well as stem and fruit, exude milky latex. Flowers are purplish to rosy pink to mostly white or even greenish and about 2 cm (0.75 in) long and 1 cm (0.4 in) wide. They occur in semi-spherical umbels (umbrella-like clusters) in the upper leaf axils. Flowers are somewhat complex in their structure, with structures not found in the average flower. The flowers are strongly and sweetly scented.

The fruits (pods), known as follicles, are formed from the union of multiple flowers. They are green, covered in soft spiky projections and are finely pubescent. When the seeds are mature, the follicle splits exposing the seeds. Each seed is equipped with a coma, a soft group of hairs. As the newly exposed seeds dry, the hairs of the coma expand allowing the seed to catch a ride on the wind. When broken, the leaves, as well as stem and fruit, exude milky latex.

Common milkweed is a widespread and somewhat weedy species. It is known from most of the eastern U.S and the eastern-most prairie states as well as southern Canada from New Brunswick to Saskatchewan. It is frequently found in fence rows, on roadsides, in fields, and in prairies and pastures. Given the opportunity, it will establish in gardens and even thin lawns. It is tolerant of light shade, but generally is a full sun species.

The genus name, Asclepias, commemorates Asklepios, the Greek god of medicine. Some of the species have a history of medicinal use including common milkweed (wart removal and lung diseases) and butterfly weed (aka pleurisy root— pleurisy and other lung disease). The specific epithet, syriaca, means ‘of Syria’ and is a misnomer: Linnaeus thought the species was native to Syria. This species is some times eaten as a salad herb, requiring multiple boilings of the young shoots before it is palatable. The reason for the boiling is to rid the shoots of various cardiac glucosides and other bitter principles. Milk weeds contain various levels of these compounds which render the plants toxic to most insects and animals. For some insects, the cardiac glucosides become a defense. They can store them in their tissue which renders them inedible or toxic to other animals. Monarch butterflies use this defense and birds leave them and the caterpillars alone. What the birds do not know is that northern monarchs feeding on common milkweed accumulate relatively little of the toxic compounds and probably would be edible. The more southern butterflies accumulate large amounts of the compounds from other species and are in fact toxic.

The stems contain a bast (inner ‘bark’) fiber used by Native Americans to produce twine and rope. The concentration and quality of the fiber make it potentially useful as a commercial fiber plant. Fiber quality is that of flax.

Common milkweed is an important pollinator and food plant for a large number of insects (more than 450 documented). It could be said that common milkweed is Nature’s mega food market for insects. Numerous butterflies, flies, bees, wasps, and beetles feed on the nectar and pollen produced by the flowers. Even hummingbirds will try, apparently unsuccessfully, to extract nectar. Aphids, especially the yellow-orange oleander or milkweed aphids (Aphis nerii), are commonly found on milkweeds including common milkweed. Large infestations of aphids can lead to formation of sooty mold on the plants which can turn the stems and leaves from green to gray to black. Two true bugs, the large milkweed bug (Oncopeltus fasciatus) and the small milkweed bug (Lygaeus kalmia) feed on the seeds, but the large milkweed bug is more often encountered. Large populations of either species can reduce the seed production potential of a colony of common milkweed by as much as 80-90%. The colorful (red with black dots) red milkweed beetle (Tetraopes tetraophthalmus) feeds on the leaves. The milkweed leaf beetle (Labidomera clivicollis), another orange-red and black beetle may feed on common milkweed but has a preference for swamp milkweed (A. incarnata). At least two caterpillars, the milkweed tussock caterpillar (Euchaetes egle) and the monarch butterfly (Danaus plexippus) feed on this plant. The red (or orange-red) and black coloration of most of these insects is known as aposematic coloration; that is, the colors advertise the fact that the organism is not good to eat. Other palatable species mimic the toxic species and gain some protection as a result. A well known example is the viceroy butterfly (Limenitis archippus) which mimics the monarch .

For monarchs, common milkweed is among the most important food plants. It is the primary food plant for northern U.S. and southern Canada monarchs and is a major food plant for monarchs in the central and southern U.S. Monarchs migrating from the mountains of Mexico lay eggs on milkweed species in northern Mexico and the southern U.S. The butterflies that result from these eggs move further north in stages, with a change in species of milkweeds utilized as they move north. Common milkweed is the usual northern species. Monarchs can be helped by encouraging existing common patches of common milkweed and planting new ones. The plant grows readily from seed and spreads quickly by deep rhizomes. Because common milkweed can be weedy and difficult to remove, care should be used to establish the plant only in places where spread can be tolerated.

The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. We occasionally feature an article from a past issue. This one, about the globally rare, and endangered, Short’s Goldenrod, Solidago shortii, first appeared in the summer of 1999, Vol. 14, No. 2 & 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.

If you would like to see this rare and beautiful goldenrod, plan now to attend the KNPS Fall Meeting on Oct. 15.

A Short Take on Short’s Goldenrod

by James Beck

Anyone out for an afternoon walk or Sunday drive in Kentucky during late August through mid October just can’t miss the bright yellows in every field and fencerow that belong to the Goldenrods (Solidago sp.). Mary Wharton considered 32 different species in the Commonwealth. Two of them, the White Haired Goldenrod and Short’s Goldenrod, are endemic in Kentucky. They are known only from our state. [Editor’s note: at the time this article was written, Short’s goldenrod was only known from Kentucky. Since then a small population has been discovered across the Ohio in at least one county in Indiana.] The White Haired Goldenrod (Solidago albopilosa), discovered by E.L. Braun in the limestone clifflines of what is now Red River Gorge, is known from 90 populations and is listed as Federally Threatened by the US Fish and Wildlife Service. Short’s Goldenrod, (Solidago shortii), listed as Federally Endangered in 1985, is both a beautiful plant, and one with a fascinating history.

This species was first collected by the eminent Dr. C.W. Short (then chair of the Medical Department at the University of Louisville) on Rock Island, which lies at the famous “Falls of the Ohio” between Louisville and Clarksville, Indiana. This is one of several islands and stony outcrops which were dry for part of the year and completely submerged for the remainder, representing the only serious navigational impediment on the Ohio River from Pittsburgh to New Orleans. Sent east for identification, the Goldenrod found at the Falls was subsequently described as a new species by Drs. John Torrey and Asa Gray, then hard at work on the landmark Flora of North America.

Civil engineering projects, culminating with the opening of a hydroelectric dam in 1930, have been historically blamed for the apparent disappearance and extinction of Short’s Goldenrod by the 1870s. It wasn’t until 1939 that the only other known population was discovered by Lucy Braun on rocky slopes and grazed pastures near Blue Licks Battlefield State Park at the convergence of Robertson, Nicholas, and Fleming Counties, Kentucky. Today 13 small subpopulations survive, all within the vicinity of Blue Licks.

The disappearance of this species at the Falls of the Ohio (which may have actually occurred some years before construction of the dam at Louisville) and its decline over the years at Blue Licks have always raised questions. Evidence exists that might support a connection between historic bison usage and S. shortii. Bison were possibly a seed dispersal mechanism, or perhaps Short’s Goldenrod benefited from the reduced plant competition that resulted from their trampling. The Falls of the Ohio represents the most logical crossing point of the Ohio River on a trail which led the bison from the Midwest to the springs and salt licks of central Kentucky. Blue Licks itself is a famous lick, one which lies on a well documented horseshoe-shaped bison trace which began at what is now Covington and made a large circuit through the region, meeting the Ohio again at present day Maysville.

Short’s Goldenrod is easily identified in the field. Totally smooth, leathery leaves and the length of its involucre (the circle of bracts or leaflet-like structures surrounding each flower) separate it out from most of the other local Goldenrod species. The Riverbank Goldenrod, (Solidago rupestris) is the most similar in form, although simple habitat differences (riverbanks versus dry, glady conditions) should end any confusion. Three other Goldenrods, S. altissima, S. ulmifolia, and S. nemoralis, grow with S. shortii at Blue Licks, but sufficient morphological differences exist between them and Short’s, and anyone with a little patience and basic knowledge of terminology should have little trouble finding it.

Short’s Goldenrod is not included in Wharton and Barbour’s Kentucky wildflower guide. The best key to it is the key to Solidago in Gleason and Cronquist’s Manual of the Vascular Plants of Northeastern United States and Adjacent Canada.

The easiest viewing of this rare species occurs in the Kentucky State Nature Preserve Commission’s Buffalo Trace Preserve, which is in the vicinity of Blue Licks Battlefield State Park. A truly unique and enjoyable day trip for any Kentuckian would be traveling from Lexington though Paris and on to the Park, all on US Highway 68. In just a few hours one could enjoy the majesty of the Bluegrass horse farms and the beauty of probably the rarest variety of our state flower.

The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. We occasionally feature an article from a past issue. This one, about a rare shrub native to Kentucky, sweet fern (Comptonia peregrina), first appeared in the spring of 2011, Vol. 26, 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.

Sweet fern—A rare Kentucky shrub with an interesting history

By Tara Littlefield, Botanist, Kentucky State Nature Preserves Commission

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.

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 ex-change).

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 in Ohio, 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, sweetfern 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 specie 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.

Berry, Edward W. 1906. Living and Fossil Species of Comptonia. The American Naturalist. Vol. 40, No. 475, pp. 485-524.

Darlington, Emlen. 1948. Notes on some North American Lepidoptera reared on Sweet Fern (Compontia as-plenifolia Linnaeus) with Description of new species. Transactions of the American Entomological Society (1890-). Vol. 74, No. 3-4, pp. 173-185.

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. Re-view of Paleobotany and Palynology. Vol. 163, p. 52-63.

Medley, Max and Eugene Wofford. 1980. Thuja occidentalis L. and other noteworthy collections from the BigSouth Fork of the Cumberland River in McCreary County, Kentucky. Castanea. Vol. 45, No. 3, pp. 213-215.

Natureserve Explorer, 2010.http://www.natureserve.org/explorer/servlet/NatureServe?searchSciOrCommonName=comptonia&x=7&y=7

Wilkins, Gary, Delcourt, Paul, Delcourt, Hazel, Harrison, Frederick, and Turner, Manson. 1991. Paleoecologyof central Kentucky sicne the last glacial maximum. Quaternary Research. Vol. 36, Issue 2.

Virginia Tech Woody Database http://www.dendro.cnre.vt.edu/dendrology/syllabus2/factsheet.cfm?ID=869

Zomlefer, W. 1994. Guide to Flowering Plant Families. University of NC Press, Chapel Hill.