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You can usually recognize H. trachypleura by the big domes of little yellow flowers and the wiry leaves. It grows in a lot of sunlight, often in disturbed areas.
When you're in an area where H. trachypleura grows, there seems to be a lot of it. But those places are few and fairly far between: about 8 counties in Colorado, a few in southeastern Wyoming and some in New Mexico.
The inflorescence is a compound umbel.
Umbels are a cluster of flowers shaped like a dome. The flowers are on the end of stems, called pedicels, that are all about the same length and all start at the same point. That point is at the end of a stouter stem called a peduncle.
It's kind of like the ribs of an umbrella.
A compound umbel is a big umbel made up of a lot of small umbels.
For H. trachypleura there are about 15 - 20 florets in each of the small umbels. About 15 - 25 of the small umbels make up the big umbel.
The shape of the umbels range from just slightly convex to almost half a sphere.
The leaves are finely dissected into long, narrow lobes. They look like dill, but larger.
The plants are usually 15 - 30 cm tall. The stems are mostly upright, green and ribbed.
H. trachypleura blooms early, in April, May and June. It's native to Colorado, New Mexico and Wyoming.
The name of the genus, Harbouria, comes from J. P. Harbour, a botanist who collected around Colorado in the 1862 with E. Hall and the more famous C. C. Parry.
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