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Isotria Medeoloides – a rare orchid

Orchid Culture and Rare Orchids

We have so many exceptional students at ACS on Shruti Dube has kindly agreed to let us publish this article on our website about rare orchids. A great read for horticulturalists and horticulture students alike -  

"The orchid family is the largest and one of the oldest flowering plant families on the earth with approximately 25,000 species found worldwide. There are more than 200 orchid species in North America. According to some studies more than half of these species have been endangered or threatened because of the destruction of its woodland habitat for development or forestry.



Among the list of threatened orchids one of them is a small-whorled pogonia called Isotria medeoloides. This species is threatened at the national level. It was first discovered by Frederick Pursh in 1814 and has since been considered the rarest orchid east of the Mississippi. It is globally imperiled, with most of the world’s populations in the states of Maine and New Hampshire in the United States. It is endangered in 16 of the 20 states where it remains. Pennsylvania, New Jersey and Kentucky in the United States have also lost this species.

I. medeoloides is a small, perennial orchid with 4-6 elliptical, pointed, grayish-green leaves which form a whorled ring around the upper part of stem. This distinctive leaf whorl gives the plant its name. The plant bears pale green flowers with the light yellow to pale green or white labellum. It prefers to grow in acidic soil and in young, open-canopy forest with beech, birch, maple, oak and hickory. The flowering period of small whorled pogonia is from mid-May to mid-June with flowers lasting from a few days to a few weeks. A plant stays in flower from 4 to14 days.  The flowers do not have any nectar and fragrance. There is no evidence of insect pollination or asexual reproduction. It is believed to be self pollinating. After pollination the fruit begins to develop and it reaches maturity in late summer and then split opens in late fall (Oct-Nov). Seeds are very tiny dust like with no stored energy. It is a non-clonal perennial species so reproduction by seed is an essential component of its population ecology.

Six closely-related fungi that work for Isotria have been found by scientists. Orchids depend on the supply of right fungi for their survival and the fungi that Isotria needs depend on trees. They found that species of Russula and Lactarius that can be associated with I. medeoloides are hosted by many ectomycorrhizal trees like oaks, beech and hickories etc. The fungi were identified from DNA sequences obtained from roots of the trees.  Botanists from Smithsonian have found that in Maryland, USA Isotria’s fungi interact with the roots of oaks, beeches and hickories and that typically occur in mature forests. If a forest is cut for any reason those old trees will be replaced by different trees and that may not be a favorable environment for orchids to grow again.

Different conservation steps have been taken and more has to be done to protect this species from extinction. Smithsonian Environmental Research Centre ecologists Dennis Whigham and Melissa McCormick are actively involved in conservation work and attempting to bring this orchid species back. They are trying to piece together a much larger puzzle connecting orchids, roots of trees, and microscopic fungi. Since 2008 they have monitored and doing research on Isotria’s population in the state of Virginia at Fort A.P. Hill (APH) and Prince William Forest Park (PWFP). Their research work was also extended to cover I. medeoloides populations in Shenandoah National Park (SNP), the Blue Ridge Parkway (BRP), and Quantico Marine Base, VA. In 2013, they began studies of a newly discovered population of I. medeoloides in Monongahela National Forest and a second site that was discovered on private property. Both sites are located near Elkins, West Virginia. They developed consistent methods for monitoring them.  Their populations require long term monitoring because some individuals go dormant.

During their research at APH and PWFP they found that a low abundance of mycorrhizal fungi in the soil and low light availability could be the cause of decline of population of I. medeoloides and its high rate of dormancy. At some places where canopy was thick they had it thinned out and that helped the population grow. It was apparent that the emergence of new plants, flowering and fruiting depends very much on good amount of light. Monitoring results have shown that greater availability of light makes orchids less dependent on their fungi.

Ongoing monitoring and research are revealing much about its biology and the best methods for its conservation. Abundance of orchids in any given area indicates better health of an ecosystem. Orchids thus, can be regarded as keystone species in forest ecosystems. So saving Isotria medeoloides is ultimately saving the ecosystem!"

Written by Student Shruti Dube

Student of Orchid Culture Course

[22/10/2021 05:39:19]

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