Research Report #46 — Pink Lady-Slipper
By: Mohonk Preserve
Tags: Plants, Flowers, Environment, Nature, Conservation

For many years scientists and naturalists have been studying and observing the flora and fauna of the Shawangunk Ridge. Foremost among them was Daniel Smiley, for whom Mohonk Preserve’s Daniel Smiley Research Center is named. Dan wrote numerous reports summarizing his observations on various topics. This regularly occurring series will feature some of these reports; some hold tremendous scientific value today and just await an interested researcher to follow up, others showcase a quirky sense of humor or highlight an oddity of nature.

Read the Report: Pink Lady-slipper. August 1977. Daniel Smiley.

A Note from Paul C. Huth, Director of Research Emeritus: The Pink Lady-slipper, Cypripedium acaule, is a member of the Family Orchidaceae, and is one of two members of this native, perennial genus that are documented in the Shawangunk Mountains. The other is the Yellow Lady-slipper. The status of the Pink Lady-slipper is considered by the New York Flora Atlas to be “relatively secure.” Dan Smiley notes in this Research Report, “In the Northern Shawangunks the Pink Lady-Slipper….is found quite generally, but sparingly, on thin-soil dry sites.” In 1924, State Botanist Homer D. House, in his important work, “Annotated List of Ferns and Flowering Plants of New York State,” gave the status of the Pink Lady-slipper as “Common throughout most sections of the State where the soil is not strongly calcareous.”

Pink Lady-slipper © Renee Zernitsky

Dan prepared this report in August 1977, to see if there was any change in the distribution and population of this species, in relation to the decline he had documented for the Yellow Lady-slipper a few months earlier. In this report, Dan looked at records from four locations in the vicinity of Mohonk where historically plants and bloom had been noted, and in some cases, blossom counts were made. The first record of a Pink Lady-slipper in Dan’s Species Card File is for one “seen in bloom” near the Mohonk House on 22 May 1931. For when to look for blooming, Dan noted from the record that an average spring blooming date was “May 20th” for 16 years during the period 1952 thru 1977. Earliest was on 4 May, and latest was noted on 1 June. Bloom lasted, depending on the weather during the blooming period, for about three weeks.

Pink Lady-slipper Herbarium Specimen © Mohonk Preserve Daniel Smiley Research Center Archives

As for indicative trends over a short timeframe, Dan used a lady-slipper stand in open pine woods south of Sky Top where, in 1964, 85 flowers were counted in a relatively concentrated area. In 1968, there were 28, 1969–15, 1970–28, 1972–0, 1973–3, and 1974–1977–0. The number of plants without flowers also declined from 43 to 10. Assessing the larger picture, Dan noted “the canopy has remained much the same….and has not changed significantly in closure….(but) there has been some increase in the shrub zone.” Curious, at another stand where Dan’s brother Keith Smiley had counted 58 Pink Lady-slipper flowers in June 1968, a repeat count of the same area by Dan in May 1977, revealed only 3. Later inspections at both sites by Mohonk Preserve Research staff revealed a continued population but at a very low ebb.

White Lady-slipper © Mohonk Preserve Education Outreach Coordinator Christy Belardo

Where usually vigorous stands of Pink Lady-slippers are found, occasionally an albino, or white-flowered form, can be found. Most have pure white flowers, but occasionally they can be “seen with pink veins.” Dan reports that from his records, “albinos of this species have been noted often,” many times though only revealing single plants in a stand. A staked plant in one stand “continued to have white blossoms for 9 years.” Dan recalled that his father had known of “‘patches’ of white ones at three locations” in his time. Dan made visits to these sites and found the stands barely hanging on.

Pink Lady-slipper © Renee Zernitsky

Dan revealed from assembling this Research Report that he “had not been aware of the decreasing number of Pink Lady-Slippers” at the previously known stands around Mohonk. “The cause of these decreases is unclear to me.” But from his years of field experience, he offered possible causes, including “increasing competition from other plants….climatic fluctuations….acid rain or pollutants….stands may be running out….(and) Deer browse.” Dan noted in one white pine grove which had supported a lady-slipper stand, there had been “some loss of large old white pines with a carpet of needles underneath.” And, while some pines remained, there were no lady-slippers. Dan wondered if “perhaps, the exclusion of fire from this area in the last hundred years has decreased conifer reproduction and permitted increased competition from (mountain) laurel.” Later, Dan also considered the dependency of orchids, and most other terrestrial plants for that matter, on their vital relationship with mycorrhizal fungi in the soil, but which could not then be easily observed or measured.

Mohonk Preserve Research Associate Ilse E. G. Biedermann, at a staked plot of Pink Lady-slippers © Director of Research Emeritus Paul C. Huth

In 1989, as a result of a Mohonk Preserve research agreement with scientists at the Brooklyn Botanic Garden Research Center in Ossining, Research Scientist Ilse E.G. Biedermann, a plant tissue culture and orchid specialist, was appointed a Preserve Research Associate, to study population declines of Pink and Yellow Lady-slipper Orchids in relationship to mycorrhizal fungi. Ilse’s premise was that these “Lady’s-slippers can only exist with a mycorrhizal fungus that pre-digests the necessary nutrients from the soil.” In three different stands over several years she staked and documented vigorous blooming lady-slippers and non-blooming leaf pairs, rated individual plant vigor, treated some with mycorrhizal inoculate, and changing soil pH surrounding others by adding lime. In her laboratory, Ilse developed a population of Shawangunk lady-slippers in tissue culture, where mycorrhizal manipulation could be investigated. One of the reveals of Ilse’s research was the significant role of soil moisture, or lack thereof, at critical times for plants in generally dry locations and for germination and survival of young moisture reliant plants and their dependent mycorrhizae over time.

Mohonk Preserve volunteers and naturalists Barbara Petersen and Roger Roloff © Mohonk Preserve

Serendipitously, a stand of Pink Lady-slippers on the Northern Preserve, noted by Dan in 1941, was found and became of interest to naturalists and Preserve volunteers Barbara Petersen and Roger Roloff as part of their annual spring botanical field trips, and which they included in Preserve Spring Wildflower Public Programs which they led for 16 years. The size of the stand and number of blossoms noted in steep Chestnut Oak and Pitch Pine dominated forest was of particular interest. In May, 1996, Barbara and Roger began exploring the stand and counting blooming plants and non-flowering leaf pairs in this ridge summit location. Of interest to the Preserve Research staff, on 22 May 1999, they counted “183 blooming flowers and 106 flowerless leaf sets”, and in one part of the stand, “was one white lady’s-slipper, with other flower parts either light green or white.” In 2002, a lower number of flowers and plants they felt might be related to dryness in the summer and fall before.

Pink Lady-Slipper © Barbara Petersen

In 2005, Barbara and Roger extended the count area to include another rich nearby section of plants. Becoming experienced with general plant characteristics, that year they also noted many flowering plants “had shorter stems than we remember in other years, but many had stems up to 17 inches too. The shortest blossom barely nosed above pitch pine duff in a favored haunt….” Their counting has continued to the present, this spring reaching 24 years! These “Pink Lady’s-Slippers seem to be thriving on these sections of the ridge. In our annual counts….the totals (while quite variable year to year) have increased….”

One wonders if the size and extent of this Pink Lady-slipper population provides a more stable, widespread, and readily available mycorrhizal fungus resource for sustainable plant growth and reproduction.

Read the Report: Pink Lady-slipper. August 1977. Daniel Smiley.