Three Varieties of the White Bog Orchid

The White Bog Orchid, Platanthera dilatata, has three varieties, though these varieties are not immediately evident to the casual observer, since they involve primarily the length of the spur and that is often hidden by the flowers themselves or by the bract on the stem of the flower.  This difference may seem of little account and not sufficient ground for considering these to be different varieties, but as Paul Martin Brown points out in his Wild Orchids of the Pacific Northwest and Canadian Rockies, this difference in spur length as well as the fact that they have different ranges "may be related to specific pollinators."

The ranges of these three varieties overlap a great deal.  We know several areas where two varieties or even all three varieties can be found, but very seldom are the different varieties found growing intermixed with one another.  They all have the same fragrance, so strong that the whole area will be perfumed on a warm and still day, so if the difference does indicate different pollinators, one would think that the pollinators are at least the same kind of insect, perhaps butterflies or moths., and indeed we have seen butterflies feeding from these flowers on several different occasions and in different locations.

The variety with the shortest spur is Platanthera dilatata var. albiflora.  This variety is not as common as the next, but we have found it fairly frequently.  Where found it seems to be abundant.  It is this variety which is believed to hybridize most easily with different species of the green Platantheras.

The second variety is Platanthera dilatata var. dilatata, which has a spur that is about the same length as the lip.  This variety is by far the most common and we have found it growing all over the Pacific Northwest, often with Platanthera stricta and sometimes by the thousands in every wet area.

The third variety is, in our experience, the rarest.  It has a spur that is much longer than the lip and for that reason also more noticeable than the spurs on the other varieties.  Though we have made a point of looking for this variety we have found it in only a few widely separated locations.

All three varieties are prone to having flowers in which the lip is caught in the "hood" formed by the petals and sepals, so that the flowers are not fully open.  Variety dilatata seems most prone to this, and we have found flower spikes on which very few of the flowers are fully opened.

One other variation has to do with the shape of the lip which in all the varieties is "dilated" (broadened) at the base.  Very often in varieties albiflora and dilatata this "dilation" is so sharp that the base of the lip looks almost square.  We have never this in variety leucostachys.

Note: these notes are to be taken only as observations and not as having any scientific authority.

Platanthera dilatata in the Canadian Rockies

One of the joys of traveling in the Canadian Rockies from mid-June to mid-July is seeing the Bog Candles, so very aptly named, in every wet location along the highway.  Driving the Yellowhead Highway we began to see them along the road north of Blue River and saw them again along the road from Tete Jaune Cache all the way to Jasper National Park.

They are often growing by the hundreds and even thousands in open boggy areas and their white flower spikes stand out like candles amid the surrounding vegetation.  When one stops to examine them more closely their sweet fragrance is almost overwhelming.  They certainly are one of the attractions of  what is often a long and tiring drive.

We found two varieties on this trip, the short-spurred Platanthera dilatata var. albiflora (below), and the mid-length spurred var. dilatata, the two varieties often growing and blooming together.  The latter is considered to be more common but we found both varieties in abundance.  Neither seemed to be more common than the other, though we made no counts.

Bog Candles (Platanthera dilatata)

This is the easiest of the Platantheras to identify on account of its pure white flowers and its sweet scent. Its white flowers make it more visible than some of the other species, and its scent perfumes the air wherever it grows.  It is very common, but always worth seeing.

We have found it on almost every hiking trip and along the roadsides in every mountainous area of the Pacific Northwest, often by the thousands. Along the Yellowhead Highway in the mountains of British Columbia, for example, we have seen it blooming mile after mile in every marshy spot.

There are three varieties of this species, distinguished by the length of the spur, which probably indicates different pollinators for each. Var. albiflora has a spur shorter than the lip, var. dilatata a spur the length of the lip and var. leucostachys, a spur much longer than the lip.

The plants can be quite short, around 20 cm, but are often much taller, around 100 cm. The 2 cm flowers are crowded along the length of the stems in large numbers, often over 100 flowers per plant. We have noticed that quite often the lip catches in the dorsal sepal so that the flower does not open completely.

There are several natural hybrids of this species and its varieties with P. stricta and sparsifolia.  These usually resemble P. dilatata, except for the flower color which is greenish, rather than pure white.  The only one of these natural hybrids that we've seen has been sufficiently different to warrant a separate post.

This species also ranges from Alaska across Canada and the northern United States as far south as Pennsylvania and Indiana, California and New Mexico. Varieties albiflora and leucostachys, however, are more limited in range, and can be found only in the western United States and Canada.

Variety albiflora

Variety dilatata

Variety leucostchys