Two Orchids at Tar Hollow

Yesterday I spent the day at Tar Hollow State Park. A good chunk of that time was spent walking the wrong way towards where I thought my car was parked and then subsequently realizing my mistake and backtracking a few miles, but the rest of the time I was looking for the Large Whorled Pogonia orchid (Isotria verticillata).

This orchid is really beautiful with greenish brown flowers, whorled leaves, and a bumpy labellum (the term for the bottom petal of an orchid flower) used to guide pollinators. It is a member of the orchid tribe Pogonieae, which comes from the word “pogon”, which means bearded. This orchid is noteworthy due to its close relation to an orchid that is commonly considered the rarest orchid in North America, the Small Whorled Pogonia (I. medeoloides). Besides the difference in size, the Large Whorled Pogonia differs from its less common cousin in color, scent, clonality, and frequency of outcrossing (1). Small Whorled Pogonia gets its specific epithet from its similarity to immature cucumber-root (Medeola virginiana), which frustratingly often co-occurs with both species of Whorled Pogonia. These plants were very common at Tar Hollow and I did a few double takes as I walked along the trail to make sure I was not overlooking the orchid I was searching for, mistaking it for another cucumber-root.

As I was walking along the road (tragically, in the opposite direction of my car as I would later learn), I glanced up on the hill beside the road and quite unexpectedly saw two Yellow Lady Slippers (Cypripedium parviflorum) in full flower. The only other time I have seen this orchid in flower is at Clear Creek Metro Park where they are enclosed in a cage to protect them from poachers and deer. There are several subspecies of Yellow Lady Slipper, and they are thought to hybridize with each other and other species of Cypripedium making identification to subspecies difficult (2). The labellum of Lady Slipper orchids acts as a trap for pollinators so once they enter, they must pass the reproductive parts of the flower to make their way out (3).

I was really happy I got to see the Whorled Pagonia orchid in flower and even though my legs are very sore today from my blunder, if I had gone the correct way to my car I wouldn’t have seen the Yellow Lady Slippers. Next time I go to a new park in search of orchids (which will certainly happen before May is over), I will plan a route and bring a map.

Sources: 1, 2, 3

More Photos from Tar Hollow State Park

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