Lesser Butterfly Orchid (Platanthera bifolia) is similar in general form to the Greater Butterfly Orchid but can be distinguished by looking into the "throat" or spur of the flower.
In this species the throat is narrow and closed, with the two pollinia (egg-shaped masses or clumps of pollen) lying parallel and close together. The spike is also narrower in overall appearance, and in general the individual plants are smaller than those of the Greater Butterfly Orchid (but robust specimens occur which can contradict this general rule).
All names: Platanthera bifolia (L.) Rich.; Habenaria bifolia (L.) R.Br.
NBN Atlas mapping: Species account : NBN Atlas UK Species Observations database
iNaturalist: Species account : iNaturalist World Species Observations database