Here in the Pacific Northwest and up into Canada there are five Piperia species, though two others have been reported periodically from Washington and Oregon, but without verification. The Piperias have been separated from the genera Habenaria and Platanthera. They share a tuber-like root, very slender spikes and flowers with similar-looking lips and petals. The leaves of all these species almost always wither around the time of flowering, so that the flower spikes appear as leafless stems. The two unverified species are Piperia leptopetala, the Lace Orchid, and Piperia michaelii, Michael's Piperia. The five species known to grow in our area are as follows:
Piperia unalascensis, the Alaskan Piperia.
This is the most common of the five Piperias and has the widest range, growing from Alaska south to California and east across southern Canada and the northern United States into the Great Lakes region. It is also, in my opinion, the least attractive of the five species, with small green or greenish-yellow flowers. It can grow in large clumps and to a height of over 80 cm, and the flowers, though numerous are less than 1 cm in size and have a tiny spur that is barely visible.
There is a dwarf form of this species, forma olympica, that grows only in one location in the Olympic Mountains (these last two pictures show this form).
Piperia candida, the Slender White Piperia.
Piperia candida has been recently separated from Piperia unalascensis and the flower color is the most obvious difference. Its flowers are white instead of green, though there are also differences in the shape of the spur and in the fact that this species has a day-time though faint fragrance. In plant size, flower count, bloom time and habitat it is is like the Alaskan Piperia, but in our experience is somewhat more rare than its green cousin.
Piperia elegans, the Elegant Piperia.
The Elegant Piperia is rightly named and the most attractive of the five species. The plants can be very large, over 80 cm with numerous, tightly packed flowers that are somewhat larger than those of the previous two species, but still smaller than 1 cm. It, too, has a faint fragrance but a much longer spur, that is nearly 1 cm. Is is quite easily identifiable and cannot really be mistaken for any of the other species. The tall plants with their white, long-spurred flowers are distinctive
Piperia elongata, the Long-spurred Piperia.
This and the following species are quite easily confused. In plant size, number of flowers, size of flowers and length of spurs they are very similar. The plants are 60 cm or less and they have numerous flowers more or less crowded on the stems. This species, however, has flowers that are dark green with a spur that curves downward, often paralleling the stem. The flowers, though small and less than 1 cm in size are quite attractive with their long, 1.5 cm spurs.
Piperia transversa, the Flat-spurred Piperia.
The Flat-spurred Piperia is named not for the shape of of the spur but for its position, one of the distinguishing characteristics. The flowers are the same size as Piperia elongata and the spurs the same length, but the spur is held horizontally and in some cases even curves upward a bit. That and the white flowers with a green or yellowish green mid-vein to each of the segments separates this from the Long-spurred Piperia.