Black Rock Canyon at Joshua Tree

A Joshua Tree in the lower Black Rock Canyon.

Joshua Tree National Park was the final NPS stop on my April loop through the Southwest. The park straddles the border of the Mojave and Sonoran deserts, the former encompassing the northern part of the park and extending up to Death Valley, and the latter desert encompassing the southern portion of the park.

Arriving after dark after driving through Kingman, AZ, Mojave National Preserve, and a short segment of old Route 66, I camped in the north central part of the park at the Indian Cove Campground. It was not crowded and a lovely spot, encircled about by the large fractured boulders that are one of the common landscape features of Joshua Tree. The morning light revealed all of the flowers present near my campsite, especially yellow patches of Desert Senna. The area looked like a tended garden with rocks and the lovely flora.

Packing up camp, I drove to the northwest corner of the park for a hike up Black Rock Canyon. There is another campground at the trailhead with a series of trails that radiate to the east and south. The canyon is initially wide, sandy, and full of the other iconic feature of the park: Joshua Trees (Yucca brevifolia). I saw (and heard) several quail in this area including a pair or two. The birds quickly scurried to and fro over the ground, not at all interested in getting close to a human.

Quail at Black Rock Canyon.

With some elevation gain heading along the trail to the south, the valleys grew narrower and rockier, and new woody species and more flowers became evident. I first noticed juniper, then pines (Pinus monophylla) and oaks. Joshua Trees were still present, as was the related but shorter species, Mojave yucca (Y. shidigera).

There were many flowers in bloom, including orange desert mallow (Sphaeralcea ambigua), the common desert dandelion (Malacothrix glabrata), bladderpod (Peritoma arborea), and Wallace’s woolly daisy (Eriophyllum wallacei), a tiny yellow aster found in sand along the edges of the trails. I also observed vines and fruits of wild cucumber, a plant not uncommon in the chaparral of coastal California, with its spiked fruits shaped like kiwis. The fruits in this area were particularly large and seemed to be among the largest I’ve ever seen of this species.

Diversity of blooming plants. Clockwise from upper left: Sphaeralcea ambigua (desert mallow), Phacelia sp., Malacothrix glabrata (desert dandelion), Salvia columbariae (chia), Layia glandulosa (white tidy-tips), and Eschscholzia glyptosperma (desert gold poppy). 

Many cacti were in bloom with their very showy flowers. The beavertail (Opuntia basilaris) had large flowers with concentric layers of ruffled pink petals. There were similarly-colored flowers on the hedgehog cactus (Echinocereus engelmannii) and red blooms on the related E. mojavensis. The flowers of the beavertail had a sweet, perhaps fruity, smell that seemed familiar but I could make the association in my mind.

Blooming cacti. Left: Opuntia basilaris (beavertail cactus). Center: Echinocereus engelmannii. Right: E. mojavensis.

The Black Rock Canyon area had an interesting assortment of wildlife too: the quail previously mentioned, many flying insects, chipmunk, and lizard. I had to pass a swarm of bees on the trail that was congregating around the tiniest of water holes seeping from a rock.

More desert fauna. The bees at right were congregating around a very tiny water
seep from a desert rock.

I am still learning about the differences among the various deserts of the Southwest. The Mojave is the smallest and driest of these deserts (MacKay 2013). Various maps show somewhat different boundaries between the southwest deserts, but basically the Mojave Desert stretches from Joshua Tree NP in the south to the Landcaster area in the west, Death Valley National Park in the north, and the southern tip of Nevada and northwest corner of Arizona to the east (Pavlik 2008, Mackay 2013). To the north of the Mojave is the cooler desert of the Great Basin that encompasses most of Nevada, while to the south and east is the Sonoran Desert that stretches south into the Baja and Sonoran regions of northern Mexico.

Two perspectives on the geographic extent of the Mojave Desert and nearby deserts in the US Southwest. My travels through the Southwest took me through the Great Basin, Colorado Plateau, Arizona/New Mexico Plateau, and Mojave Desert. Base maps from the USGS and EPA; in the public domain.

Sunrise at the Indian Cove Campground.

Some characteristic species can help guide one through the various deserts of the region. The Joshua Trees are indicative of the Mojave, occurring in places from NW Arizona to Joshua Tree to the high desert north of Los Angeles. The Sonoran desert has the iconic saguaro cactus (not seen on my trip) and the wonderful ocotillo with its flaming branch tips of red flowers. I did not see ocotillo in the northern part of Joshua Tree (which is Mojave territory), but saw it in abundance at the southern end of the park on a previous trip (that area is Sonoran territory). Interestingly, I also saw a population along Interstate 40 south of Kingman, AZ.

The Mojave Desert has a high diversity of plant species (>2600), a wide range of elevations which provides for a diversity of habitats, and a rate of plant endemism of about 25% (MacKay 2013). Mackay (2013) suggests the area may be under-explored botanically, with the possibility of future plant discoveries.

References

MacKay P. 2013. Mojave Desert Wildflowers. 2^nd ed. Rowman & Littlefield

Pavlik BM. 2008. The California Deserts. An Ecological Rediscovery. University of California Press, Berkeley, CA.