There are three members of the Platanthera hyperborea complex in Manitoba. These are Platanthera dilatata (Pursch) Lindley (tall white northern bog orchid), Platanthera aquilonis Sheviak (northern green bog orchid) and Platanthera huronensis (Nuttall) Lindley (green bog orchid).

All three of these species bloom from mid June until early August with the prime blooming period in mid-July. Platanthera aquilonis and Platanthera huronensis range widely in Manitoba from the south to at least Churchill in the North. Preferred habitat of these two species is moist ditches and meadows in the prairies and parklands, and open fens and bogs or moist sedge meadows of the northern coniferous forests. Platanthera dilatata does not range as far north, with the northernmost collected specimen from the Split Lake/Gillam area. This species can be found in open fens and bogs, on floating sphagnum mats and moist sedge meadows in undisturbed areas. Platanthera dilatata is normally found in habitat that is wetter than where you would find the other two species.

Platanthera dilatata is easily identified as it has pure white flowers, a lip that is moderately to strongly dilated and has a spur that is usually slender and is about the same length as the lip. The fragrance of clove is characteristic. The other two species of this group create a great deal more difficulty in identification and the purpose of this article is to provide some guidance that may be of assistance in the field.

Photo 2: Partial inflorescence of Platanthera aquilonis. Note the lip colour and the spur size, shape and position. Pollinia can be seen rotated downward.	Photo 4: Close-up of Platanthera huronensis - allogamous type. Note position of anther sac: upright, nearly parallel with the pollinia retained.
Photo 3: Close-up of Platanthera aquilonis blossom. Note the position of the anther sacs: diverging at the base close at the apex and the downward rotation of the pollinia.	Photo 5: Close-up of Platanthera huronensis - autogamous type. Note position of anther sac: upright, nearly parallel with the pollinia rotated downward from the anther sacs.

Cytological studies by Dr. Charles Sheviak during research on this complex noted that within the green flowered plants of this group, some were diploid (two sets of chromosomes) while others were tetraploid (four sets of chromosomes). It was this revelation that led Sheviak to look carefully at the morphology of the flowers and resulted in the recognition of the new species Platanthera aquilonis. Platanthera aquilonis is diploid while Platanthera huronensis is tetraploid. This cytological information is of not much assistance in the field except for the fact that occasionally the tetraploid (Platanthera huronensis) will produce extremely robust specimens.

In the field Platanthera aquilonis can usually be identified by a dull yellowish coloured lip, that has nearly straight sides with angles rounded but not dilated. The spur is stout, club shaped and blunt, about 3/4 of the length of the lip but often appears shorter because it is curved sharply forward with the tip of the spur beneath the middle of the lip. The flowers are scentless and are autogamous (self-pollinating). Occasionally because of environmental conditions or flower variability, these described characteristics are not distinct and may appear similar to those of Platanthera huronensis. For more conclusive identification, a magnifying lens, preferably a 10X loupe, should be used to examine the structure of the column and manner of pollination. The anther sacs of Platanthera aquilonis are low and spread widely at the base with the tips close and almost touching. Self-pollination occurs as the pollinia rotate forward out of the anther sac and contact the stigmatic surface, the pollinia sometimes breaking up and spilling pollen grains.

Platanthera huronensis characteristically has whitish-green flowers that could also be described as an icy-green colour. The lip is lance shaped with the base moderately to roundly dilated and is not yellow as with Platanthera aquilonis. The spur is often simply pendant or may be slightly forward curved and may vary from being a slender cylindrical shape to a thicker more club shaped form. Normally the spur is approximately as long as the lip. The flowers are fragrant and can be either allogamous (cross pollinating) or autogamous. The anther sacs are elevated and almost parallel, only slightly diverging at the base and are separated at the apex. Self-pollination occurs in a manner similar to Platanthera aquilonis while in those plants that cross pollinate, the pollinia remain in the anther sacs until removed by the pollinating insect.

Please note that occasionally plants do occur which are intermediate between the two species and may be very difficult to identify. It is possible that these may be hybrids or this may simply be due to plant variability.

During a trip to Churchill in July 2003 with Dr. Sheviak and his wife, we drove to Thompson and took the train to Churchill. A number of locations along the route to Thompson and locations at Churchill were checked for the presence of these species. Both Platanthera aquilonis and Platanthera huronensis were found at many of the locations checked. All specimens of Platanthera huronensis from the Grand Rapids area and north to include Churchill were found to be autogamous. In the south, specimens of both the allogamous and autogamous types were observed.