I’ve only seen this in two trails: one, on the back side of Arroyo Burro Rd., blooming 26 June 2011 (hiked the same trail 14 June and only buds were visible). It was about 2.25 miles from Camino Cielo. N34.5196114,W119.7521541 On the left side of the road when going downhill. There was another patch about a quarter mile further down. I also so a single plant on the backside of Romero trail about ¼ mile down from the road (28 June), and then two weeks later a large patch started blooming where the road meets the trail.
Patches at higher elevation started blooming later than lower patches. Any patch seemed to bloom for at most a month.
This may be distinguished from P. michaelii (also in our area) by the shape of the bottom petal (among other things). In P. m. the bottom petal, the lip, is rounded and broad, while in P. e. the lip is triangular and thinner.