Trees
Utah juniper
The shaggy-barked evergreen of pinyon-juniper country, sometimes called Utah cedar.
Blackbrush
A tangled desert shrub of shallow soils whose branches darken when wet.
Blackbrush is an intricately branched shrub of shallow sandy to clay desert soils. Its branches darken when wet, which gives it its name. Small leaves grow in opposite pairs and are drought-deciduous: the plant drops them when conditions are too dry and grows them back when moisture returns.
Most of the world's blackbrush grows in Utah. It depends on rodents to plant its seeds; look for burrows beneath the shrubs. The National Park Service says historic photos show only 1% of the blackbrush at Arches died over 100 years, and some plants may be thousands of years old.
Seeing it
At Arches it flowers in April and May.