Echinomastus johnsonii var. lutescens

Echinomastus johnsonii var. lutescens is a yellow-flowered form of that species, known from NW Arizona. plants there have dark red-brown spines and pretty common if you are looking at the right place.
It is an interesting plant, on a larger side for any Echinomastus. Flowers are persistently yellow with red center. You can see new fruits set on older blooms of this season. They ripen very quickly, in little over one month, then splitting and dropping seeds to the ground not far from the mother plant.
Population near Searchlight NV has yellow and pink flowering plants, but that form is considered johnsonii sensu stricto.
The photograph is taken in the desert west of Wikenburg AZ, on a rolling hills with sandy soils, at the end of April. This plant is rarely seen in cultivation, mainly due to pure understanding of it cultural requirements. It is moderately quick growing plant, blooming readily at a size of about 3 inches.