Plant communities, or what we call "associations," describe groupings of various plant species that are often dependent upon latitude, soil characteristics, and elevation. Using these descriptions makes it easier to understand why certain plants only grow in certain places; it also helps to identify plants in unfamiliar terrain.
Plant associations within the park are divided into tree-dominated, shrub-dominated, herbaceous-dominated, and sparse/non-vegetated. Each association is named after the most conspicuous plant in the landscape.
Tree-dominated plant associations in Joshua Tree include: California juniper, singleleaf pinyon, Joshua tree, desert willow, ironwood, California fan palm, blue palo verde, smoketree, Gooding willow, Freemont cottonwood, and mesquite
Shrub-dominated associations are the most diverse group, numbering 49. Mormon tea, creosote bush, creosote bush/white bursage, blackbrush, brittlebush, cheesebush, Mojave yucca, teddy-bear cholla, and desert almond are just a few examples
Herbaceous-dominated associations are those communities that are mostly comprised of species like perennial bunch grasses or annual grasslands. Joshua Tree has two herbaceous-dominated associations: big galleta grass and cheatgrass.
Sparse associations include non-vegetated areas (e.g. desert pavement, rock outcrops, dunes, playas, washes, and disturbed areas) and areas with less than two percent shrub cover. These areas may be dominated by annual wildflowers during moist years, but normally appear devoid of vegetation.