The Lady Slipper newsletter, and now blog, 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. In this article from 2010, the late Tom Barnes, wildflower photographer and former president of Kentucky, takes an in-depth look at the gentians (Gentianaceae family) . This article ran in Vol. 25, No. 4. If you would like to see these and other past issues, visit the Lady Slipper Archives, where all issues from Vol. 1, February 1986 to Vol. 39, 2024, can be found.
Gentians: All Fall Color is Not Red, Yellow and Orange
Thomas G. Barnes, Ph.D.
Extension Wildlife Specialist, Department of Forestry, University of Kentucky
Fall is the time of the year when the leaf peepers begin their road trips across the Commonwealth in search of reds, yellows, oranges, and other colors in the tree canopy. For wildflower enthusiasts it is a time of the year when they think of other activities since the goldenrods and asters are done flowering and the drabness of winter is quickly approaching. For those who do love searching for unique wildflowers, like so many do for our native orchids, this is the time of the year to search for fall flowering members of the gentian family, those that typically have beautiful blue flowers. When you think of the rarity of the native orchids found in Kentucky, approximately 38% are listed as rare, special concern, threatened or endangered. Of the fall gentians, 68% fall in those same categories. So if looking for rare plants is your venue, then the fall gentians are an excellent group to focus on. I hope to share with you some information about gentians in general and then which species can be found in Kentucky.
The fall flowering gentians all belong to the genus Gentiana and there are six species: G. puberulenta (prairie closed), G. decora (Appalachian or showy), G. andrewsii (Closed or bottle), G. saponaria (Soapwort), G. flavida (Pale), and G. villosa (Striped). The Pale gentian actually is the first of the group to flower in August, typically before the fall season actually kicks in September and October. But we will include it in the discussion as well. Other members of the gentian family that reside within the state include the Screw-stems (Bartonia virginica and B. paniculata), American columbo (Frasera carolinensis), the stiff gentian (Gentianella quinquefolia), the Pennywort (Obolaria virginica) and the Marsh- Pinks (Sabatia angularis and S. campanulata).
The gentian family of 87 genera and more than 1600 species are known to occur on every continent except Antarctica. They are most often associated with the deep blue flowers found in the Rockies or the Alps but their color can vary from deep blue to pink, red and yellow. The name Gentiana (one of the largest genera in the group with more than 360 species) is derived from Greek and was originally named by Dioscorides and Pliny the Elder somewhere between 50 and 100 AD. According to these two botanical scholars, the name derived from the last of the king of Allyria (near Albania of today) Genthios who originally discovered its medicinal properties sometime between 180 and 68 BC. This given name is still used by the people of Albania and surrounding areas. Gentians were believed to have evolved from the tropics and moved north and while some species are still found in the tropics, by far the most species now occur in temperate regions of North America, Europe and Asia.
In general, members of the gentian family do not have simple or glandular hairs anywhere on the plant, they have simple, opposite, entire leaves with a prominent midrib with few secondary veins. The flowers are typically bisexual with petals and sepals that are fused at the base. The petals are often large and colorful and twisted (contorted) to the right in the bud. The stamens are inserted into the corolla tubes and the ovary is both superior and bicarpellate.
While many different creatures pollinate gentians including moths, hummingbirds, and bats, by far the most important pollinator of North American gentians is the bumblebee. These strong insects are capable of prying open the closed flowers (for species like G. andrewsii and saponaria) and accessing the pollen. Sometimes they actually chew a hole in the side of the flower and gain access. The other interesting pollination story about gentians is that most of the fall blooming species close up at night and only open on bright sunny days. Why would a plant do such an outrageous thing? The answer is quite simple. Closing the flowers at night helps protect the pollen from cold and dew or rain and ensures that the pollen is fresh when the bees begin flying when the temperature increases. This means that the pollen is less likely to spoil and remain fresh. The actual opening and closing of the flowers in the gentians is a result of expansion and contraction of the cells that form the petal.
Here is another interesting facet of the gentians. They have true blue flowers. Since blue flowers are uncommon in nature, how is this color formed by the plant? It basically involves complicated biochemistry associated with anthocyanins. These flavenoids differ from other plant pigments (like chlorophyll for green and carotenoids of yellows, reds, and oranges) in that they exhibit a wider variety of colors. When anthocyanins are found in the petal vacuoles (large sacs that make up 90% of cell volume) they produce reds, purples and blues. What complicates the equation is that pH affects the anthocyanin chromophore (that part of a visibly colored molecule that absorbs light). The creation of blue flowers results from stabilizing the blue anhydrobase anion from weakly acidic to neutral in a system which we do not understand at this time. We do understand that there are four primary ways that plants produce blue flowers: 1) generating a more oxidized chromophore (add oxygen or remove electrons), 2) increasing vacuolar pH to more neutral, 3) adding metals like Al3+,Fe3+, to the anthocyanins, and 4) stacking aromatic groups to the anthocyanin chromophore so that it absorbs a different wavelength of light. Most plants use a combination of strategies to create the blue color. It appears that the blue color in gentians is formed adding metals, oxidizing and stacking.
Once a gentian has been pollinated and the seed is mature, the seeds are primarily dispersed by wind. Many of the gentian seed pods rattle in the wind and hence the tiny seed is dispersed farther from the mother plant. If you are attempting to grow gentians from seed, the seed should be sown as soon as possible after ripening as viability appears to decrease dramatically under storage. The seeds should be sown directly onto the growing medium, do not cover with soil, and the seeds need darkness to germinate. It typically takes between two to seven years to produce mature plants that will flower and some species can’t be grown because they have an intricate relationship with soil mycorrhizae.
Now that you understand a bit about gentians, lets discover some Kentucky blues beginning with the largest and showiest of them all, the prairie gentian (G. puberulenta). Of the fall blooming species, this is the only one where the corolla is mostly open compared to the others which are mostly closed. This species is listed as endangered by KSNPC and is only known from several locations in the Mississippian Plateau area. It is a true prairie or grassland species which ranges from Canada through the Great Plains and reaches it southern distribution in Kentucky and Tennessee. This perennial reaches from three-quarters to one and a half feet tall and stays in flower for about a month. The central stem has a reddish tint and it has up to three inch long and an inch and a quarter wide leaves. It has a long stout taproot with few lateral roots. It is usually considered an indicator of original prairie habitat.
The first of the closed fall gentians is Showy or Appalachian and is listed by KSNPC as special concern. In Kentucky it is only known from the three counties with true mountains, Bell, Harlan, and Letcher and is considered a southern Appalachian mountain endemic. It typically grows on the upland, sandstone ridges and at the edge of mesic forests or openings. The color of this species can vary tremendously and I have seen specimens that are quite blue to some that are almost white. In Kentucky they appear to be more cream colored with darker blue streaks
The closed or bottle gentian (G. andrewsii) looks quite similar to the soapwort gentian (G. saponaria). These are both wetland species and can typically be found in wet grasslands or open wet woods. The soapwort gentian can be found statewide whereas the bottle gentian is found in the Interior Plateau. The primary difference between the species is that G. saponaria has rounded corolla tubes that are equal or exceed the length of the appendages between them. In Kentucky G. saponaria is listed as infrequent and andrewsii is listed as rare. Hybrids between the two species have been reported in the literature.
The pale gentian is the earliest flowering of the closed gentian species often flowering in August. It is endangered and only known from several locations and the best population occurs on private land. It is also much taller than the previous listed species and can obtain heights of three tall or more. The flower color is typically white to off-white or cream but may have a hint of yellow or green. It is synonymous with G. alba.
The final pale colored fall gentian in the state is the striped gentian, G. villosa. This plant is listed as infrequent and pretty much occurs statewide except for the gulf coastal plain region. It typically grows in dry to wet woodlands or at the edge of open woodlands. It is more typical of size for the other gentians in the state growing from six to eighteen inches tall.
On a final note, the greater fringed gentian (Gentianopsis crinata) is a particularly beautiful species that occurs at the edge of bogs throughout the northeastern states and in the high elevations throughout the southern Appalachians. It has been discovered in both Ohio and West Virginia and there is no reason not to believe that it might occur in Kentucky because like most of the other fall gentians, the plants are pretty inconspicuous when not in flower and most botanists are not up in the well known bog systems in the mountains during the fall of the year. So perhaps one day with some exploring, this wonderful species could be an addition to our flora. Then when fall weather comes around, wildflower enthusiasts will have something else to look for and for photographers, well the possibilities are limitless when shooting fall blues.