A New Variety of Saxifrage in South Carolina
Article and photo’s by Dan Whitten, Senior Master Naturalist
On Feb. 25, 2021 there was a televised news segment about a newly described plant called Shealy’s Saxifrage, which is botanically known as Micranthes petiolaris var. shealyi. P. McMillan and L. Cushman named this new plant after Dr. Harry Shealy. The segment featured an interview with Greg Lucas of SC DNR and said that it was only found in Pickens County at Nine Times Preserve (NTP). On March 8th, I saw a Facebook post of pictures of the plant and so planned my trip for March 12th to go see for myself.
Before my hike to NTP, I looked up in Weakley’s Flora (Oct.20, 2020 draft) as to what made the plant unique. I found that M. petiolaris var. petiolaris, or Cliff Saxifrage, was a summer flowering perennial while M. petiolaris var. shealyi, or Shealy’s Saxifrage, was a late winter, early spring flowering annual. The flower morphology was also different, with Cliff Saxifrage having bilaterally symmetrical petals with the upper 3 having 2 yellow spots each and the lower 2 without spots. The Shealy’s Saxifrage, according to the key and description, had five radially symmetrical petals each with the 2 yellow spots.
When I found the plants in bloom along the woodland borders at the edge of the rock outcrop, I began to take photos. I also observed most plants were flowering and had many unopened buds. But there were only a small number of flowers arranged radially with more flowers in the 3 and 2 arrangement typical of Cliff Saxifrage. This led to questions that were later answered when I read the publication that presented the argument for this being a new variety of plant. This article is in Phytotaxa 452.2.2 and entitled “Micranthes petiolaris variety shealyi: A New Variety of Micranthes (Section Stellares, Saxifragaceae) from South Carolina”. Cushman, Richards, McMillan.
According to the article, several characteristics make this plant a new variety in addition to its floral morphology.
1.) The plants have different phenology, as demonstrated by their different flowering times. The NTP population blooms from mid-Feb. to early May while the Cliff Saxifrage blooms from late May to September.
2.) The range is different. The NTP population is just outside the normal range of Cliff Saxifrage, which (in South Carolina) is in the higher elevations of Oconee, Pickens and Greenville Counties. The NTP population is at 1600’ above sea level while the other variety is well above 2000’.
3.) The plants have different durations. These lower elevation plants are annuals since they sprout from seeds each year. They see higher temperatures year round and mostly dead by June (though it has been observed that a few of the NTP plants in moister years and deeper soils have survived the summer, and these are more robust in form). The higher elevation plants (which have cooler and moister conditions) persist as perennials.
You may be wondering, how durable are these differences? To find out, a few plants from NTP and from a population at 5,200’ at Black Balsam Knob (BBK) were observed for several years in two offsite locations chosen to mimic the original sites. Even though grown side by side, they each retained their respective phenology, morphology, and duration.
So what I take away from having read about these plants is that all the early blooming plants as found at Nine Times Preserve are Shealy’s Saxifrage, even though many have a different flower morphology from the type specimen as described by Cushman, Richards and McMillan. Patrick McMillan has said that we are possibly seeing evolution and speciation before our very eyes.
For more information and some excellent detailed photos, see Jim Fowler’s blog on Nine Times.
It is possible that other populations of low-elevation, early flowering Shealy’s Saxifrage exist. Weakley’s Flora (October 2020 draft) says, “additional material perhaps matching this taxon has been found in Polk County, NC”. Also, acting on the advice of a reliable friend, I found an early spring flowering Micranthes from the Pinnacle Mountain Trail in Jones Gap SP. I am looking forward to the next chapter in the scientific community’s quest to increase our knowledge and understanding of this new variety!