Platanthera huronensis (Tall Northern Bog Orchid)
|Also known as:
|part shade, shade, sun; bogs, marshes, rocky lakeshores, wet meadows
|June - August
|4 to 40 inches
|Wetland Indicator Status:
|GP: OBL MW: FACW NCNE: FACW
|MN county distribution (click map to enlarge):
|National distribution (click map to enlarge):
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Long, spike-like raceme of 10 to 60, 3/8-inch irregular flowers. Flower color ranges from pale green to greenish white, the lower lip often whiter than rest of flower. An upper (dorsal) sepal and two lateral petals form a hood above, 2 oval to lanceolate petal-like sepals spread laterally, often curling back at the tips. The lower lip is also lanceolate though more narrowly so than the lateral sepals, and also has a slight to pronounced round dilation at the base. The tip of the lower petal often stays touching the tip of the hood above during the entire bloom period. A tubular, curved spur is behind. Flowers are typically noticeably fragrant.
Leaves and stems:
Leaves are few to several on a single stem, oblong to lance-linear, up to 12 inches long and to 2 inches wide, sheathing the stem, reducing in size as they ascend the stem and becoming bract-like in the upper plant. Stem, leaf surfaces and leaf margins are hairless.
Until recently, in Minnesota Tall Northern Bog Orchid and Northern Green Orchid, (Platanthera aquilonis) were considered to be Platanthera hyperborea, also called Northern Green Orchid but whose range is now considered limited to Greenland and parts of Alaska. There are several easy discriminators between our two species that are helpful when applicable. In Minnesota the range of P. huronensis is restricted to northern boreal forest habitats, its spike can reach nearly 3½ feet in height with up to 60 flowers, and its flowers are typically whitish green and fragrant. It also is a tetraploid species that can occasionally produce incredibly robust specimens (see images) that can have well over 100 flowers on a thick, club-like spike. P. aquilonis is diploid and will never exhibit this trait. While P. aquilonis is found throughout the range of P. huronensis, it also extends across the entire western prairie region where P. huronensis would likely never be encountered (see range maps). It rarely exceeds 2 feet in height with a maximum of 40 flowers and as few as 5, the flowers often conspicuously greenish yellow and without fragrance. Where these characteristics overlap makes field ID a challenge even for experts and requires 10x magnification and a metric ruler. The most precise information for these characteristics can be found in Welby Smith's book “Native Orchids of Minnesota”. For P. huronensis the lower lip is lance-shaped to nearly linear, 4.5-7 mm long by 1.5-3 mm wide, with a slight to pronounced dilation near the base and the anther sacs are borne upright, nearly parallel to one another above the stigma. Also the spur is typically more cylindrical and longer, 4.5-7 mm long. The hood of P. aquilonis also tends to be more flat where P. huronensis is more erect, especially when a flower is in its prime. Flora of North America has a good illustration of these characteristics. The tendency, in many specimens, for the tip of the lower lip to remain adhered to the tips of the upper sepal and petals can make close observation of these traits difficult.
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Photos courtesy Peter M. Dziuk taken ar various locations in Aitkin, Cass, Dakota, Hubbard and Lake counties.
Have you seen this plant in Minnesota, or have any other comments about it?