Similar to Platanthera orbiculata and Platanthera macrophylla, Platanthera hookeri has a pair of large rounded leaves that lie flat against the ground. In 19th-century Vermont the leaves were applied as a plaster to heal weak lungs, and to heal bruises and reduce soreness. The species was named by 19th-century English botanist John Lindley for his colleague Sir William Jackson Hooker, director of Kew Gardens in London. Lindley was instrumental in saving the garden from destruction in the 1830s.
There are four known populations. Two additional populations have been reported in the last 20 years that recent surveys have failed to relocate. Populations of this plant have declined sharply over the past 100 years. The reasons for this are unknown, but acid rain has been speculated as a likely cause.
Populations have persisted at very low levels over the past ten years. No more than five populations were known at any one time and now only two populations are known. This trend of small fluctuating numbers will probably continue into the foreseeable future.
There has been a large decline in populations of this orchid especially since the beginning of the 1950s. In the first half of the 20th century, 36 new locations were found for this orchid but only 11 in the second half of the century and none since the year 2000. Five populations were known in the 1970s but only three new populations were discovered since then and only two are still surviving today. From these data we can imagine that this orchid was not an uncommon sight in our forests before the 1950s but now it is almost gone.
The real reasons for the decline of this orchid are unknown. Substantial habitat remains throughout the state but past land management practices, habitat destruction, and other factors such as the increase in the deer herd, climate change, and pollution have all been suggested. More detailed research into its decline is needed.
Once more is known about the direct threats to these plants, appropriate management can be undertaken. With so few populations known today and the sharp decline observed over the past 100 years, frequent monitoring should take place to better understand the dynamics influencing these populations.
Research needs to be undertaken to discover why this plant is in severe decline throughout the state. More detailed studies on the demography of the species should also be done to understand the factors that influence its appearance each year.
This orchid is found in dry to moist woodlands and forest, but seems to prefer more forested areas with open understories or successional forest, particularly those dominated by poplar and pine (New York Natural Heritage Program 2005). Dry to mesic coniferous and deciduous forest (Flora of North America 2002). Rare in rich, well-drained deciduous woods (Rhoads and Block 2000). Rich moist woods (Gleason and Cronquist 1991, as Habenaria hookeri). Coniferous or mixed woods, thickets, and borders, especially on wooded dunes and sandy soil near the Great Lakes; less often in deciduous forest or hemlock-hardwoods (Voss 1972, as Habenaria hookeri). Dryish woods (Fernald 1970, as Habenaria hookeri).
Historically this orchid was reported throughout much of New York, ranging from the Hudson Valley and Adirondack foothills, west through central and western New York. Today it is only known from a few populations near Ithaca and the eastern Adirondack foothills.
A plant ranging from Newfoundland and Nova Scotia, south to New Jersey and Pennsylvania, and west to Manitoba, Minnesota, and Iowa.
Hooker's orchid grows up to 10 inches tall from two broadly rounded to widely oblong, thick, green leaves up to 6 inches long that lie flat on the ground. The green flowering stem has no leaves and is topped by an unbranched inflorescence of 10-15 yellowish-green flowers on flower stalks that arise at an upward angle from the stem. The flowers are only about 3/4 inch wide with a tongue-shaped lip that curls up at the end and a long spur that angles down at the back.
The leaves of this orchid are orbicular, broadly elliptic or oblong-obovate, lay flat on the ground, thick, 5-16 cm long, and 2.5-12 cm broad. The scape is fleshy, naked, and 7-25 cm high. The flowers are greenish or greenish-yellow, sessile in a strict spike 5-25 cm long, and 2-4 cm wide. The upper lance-acuminate sepal is 7-11 mm long and the lateral sepals are 8.5-11.5 mm long. The petals are 6-9 mm long. The lip is 9-13 mm long and the spur is 1.4-2.5 cm long.
This orchid often does not flower, and identification based solely on the leaves is difficult. Plants with a flowering stalk are easiest to identify.
Platanthera orbiculata has a scape with a few leafy bracts present and basal leaves that may reach up to 21 cm long. Its white or greenish-white flowers tend to appear later than Platanthera hookeri. Platanthera macrophylla is also bigger with very thin leaves up to 24 cm. The flowers are usually whiter than Platanthera orbiculata and with a very long spur 2.9-4.5 cm long. These two orchids bloom about 2-3 weeks later than Platanthera hookeri.
Depending where in the state you look, flowers may be observed sometime between mid-May to early August. The peak flowering period appears to be late June to early July. While plants often do not flower, surveys should nonetheless be conducted during the peak blooming period. Vegetative plants are more difficult to locate and identify.
The time of year you would expect to find Hooker's Orchid vegetative, flowering, and fruiting in New York.
Platanthera hookeri (Torr. ex Gray) Lindl.
Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.
Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.
Flora of North America Editorial Committee. 2002. Flora of North America, North of Mexico. Volume 26. Magnoliophyta: Liliidae: Liliales and Orchidales. Oxford University Press, New York. 723 pp.
Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.
Mitchell, Richard S. and Gordon C. Tucker. 1997. Revised Checklist of New York State Plants. Contributions to a Flora of New York State. Checklist IV. Bulletin No. 490. New York State Museum. Albany, NY. 400 pp.
New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.
New York Natural Heritage Program. 2021. New York Natural Heritage Program Databases. Albany, NY.
Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.
Rhoads, Ann F. and Timothy A. Block. 2000. The Plants of Pennsylvania, an Illustrated Manual. University of Pennsylvania Press, Philadelphia, PA.
Voss, E.G. 1972. Michigan Flora, Part I. Gymnosperms and Monocots. Cranbrook Institute of Science Bulletin 55 and the University of Michigan Herbarium. Ann Arbor. 488 pp.
Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research http://www.fccdr.usf.edu/. University of South Florida http://www.usf.edu/]. New York Flora Association http://newyork.plantatlas.usf.edu/, Albany, New York
Information for this guide was last updated on: August 28, 2019
Please cite this page as:
New York Natural Heritage Program. 2021. Online Conservation Guide for Platanthera hookeri. Available from: https://guides.nynhp.org/hookers-orchid/. Accessed April 13, 2021.