Wavyleaf thistle flowers are sometimes white

Description:

Cirsium undulatum (Nutt.) Spreng.While the flowers of this species most typically are pink to rose-violet, they can also be creamy white (this is the first time I have seen a white flowered specimen of this species and it was the only Wavyleaf thistle in the vicinity that did).July 16, 2011, Wasatch foothills, Mile High area, Salt Lake County, Utah, approx. 5,000 ft. elev.Associated species included Petradoria pumilia (in flower), Cryptantha humilis (only a few plants here, with nutlets), Eriogonum umbellatum (in flower, also very few plants here), Bluebunch wheatgrass, Gambel's oak, Lygodesmia grandiflora (in flower) and others. This thistle was partly shaded; typically plants are found in completely open areas.