Blackbrush

Blackbrush often appears to be dormant during the summer months displaying dry leaves and flowers.

NPS/

The aromatic, many-branched blackbrush offers insight into past climates. Gazing at one of these inconspicuous, stubborn gray tangles of spines is an invitation to travel back in time. Approximately twelve thousand years ago, in the waning days of the cooler, wetter Pleistocene epoch, blackbrush reigned supreme. Twisty forests of it stretched to the horizon, painting the landscape that would later transform the Mojave Desert a deep, somber gray.

In this wetter epoch, blackbrush had the luxury of reproducing slowly and growing to a ripe old age. Ample moisture ensured that the shrubs would don coats of cheery yellow flowers each spring, and that the seeds these flowers dropped would germinate successfully.

Today’s visitor to Parashant National Monument can walk among the ancients in the Mojave Desert’s lower elevations. Look for dark gray mounds of Blackbrush growing on slopes. They are barely hanging on as global temperatures rise in response to climate shifts. These stands are a reminder of the way things were in the Pleistocene, when Blackbrush flourished and flowered year after year. Though heavy rains still trigger blossoming, the seeds can only germinate if the desert gets two wet winters in a row. As the favorable combinations of moisture and temperature grow smaller, these stalwart shrubs have no choice but to hunker down and wait.