A great purple hairstreak butterfly feeds on desert broom. Photo by Vince Pinto

Arizona, including our Sky Islands region, tends to be a place associated with wildflowers. Just the southeast quadrant of the state hosts approximately 2,000 species of flowering plants, a good number of which have evolved to blossom in late winter and spring. To say that this early floral pageant is mercurial is to understate the case. Precipitation, or lack thereof, renders this annual affair a decidedly fickle one. 

Late spring witnesses a pulse of flowering succulents, particularly in the cacti and asparagus (think agaves and yuccas) families. Fast forward to monsoon season and yet another salvo of flowers graces the landscape. Summer blossoms tend to be a bit more consistent than those of spring, albeit at varying levels of abundance. 

Once the monsoons have passed, an even more tenuous rain lottery ensues. Autumn is not a time to expect wildflowers in the Sky Islands. Yet they do exist, occasionally coexisting with leftover monsoon wildflowers in years of extra summer precipitation, but very rarely bursting forth with unbridled exuberance.

Given that competition for pollinators can be fierce, some local plants have evolved to largely or fully flower in fall. If soil moisture is sufficient, a good number of species are primed to take full advantage of such infrequent conditions. Some are reprises of flowers better represented at other times. Ocotillo falls into this category with occasional sprinkles of flaming red blossoms incongruously bedecking a few tips of this unique succulent. 

Most of autumn’s opportunistic species seem, however, to fall into one lone plant family—Asteraceae. The aster, sunflower, or composite family is a highly successful one. Just in the 9,000 or so acres of Sonoita Creek State Natural Area—situated just over a hill from our own Raven’s Nest Nature Sanctuary—about 86 members of the family dot the land. Few other plant families are so abundant in our region.

With the subpar monsoon season now in our rear-view mirror, expectations of a large fall bloom should be set quite low. No doubt a few species will technically fall into the autumn bloomer category even this year. The season began on September 21. Thus, any plant daring enough to bloom after that date up until the winter solstice is indeed a fickle fall flowerer. 

Usually come hell or high water, a relatively consistent autumn bloomer is desert broom. This somewhat infamous native plant gets a bad rap for its penchant for spreading in homeowners’ yards, particularly in disturbed areas. Further besmudging its reputation is the pollen that allergy sufferers must bear and the copious fluff—“Arizona snow”—that annoyingly accumulates near one’s doorstep. 

Before condemning this aster family member, however, take time to carefully observe both the male and female plants in bloom. You may well hear desert brooms before laying eyes on the flowers, so rife are they and so loudly abuzz with visiting pollinators. Native bees, non-native honeybees, wasps, various fly species, a bevy of beetles, bountiful butterflies, some true bugs, and others fairly make the terminal whitish flowers writhe with activity. There to feast upon them are mantids, assassin bugs, birds, and other predators of invertebrates.

This much maligned, yet crucial, plant is not alone. Joining it are a host of other aster family members. At Raven’s Nest we often admire both yellow and purple spine asters here at 4,000 feet. In Madera Canyon, look for goldenbush— an evergreen sporting rich yellow flowers that smell of honey. They ride above the evergreen foliage that itself smells richly aromatic when crushed. Out in the San Rafael grasslands, search for tall vigueras with their yellow flowers. (Yellow seems to be the autumn flower color now in vogue, evolutionarily speaking.) Even taller sunflowers may join the vigueras, especially along the side of the road. Up in the soaring heights of our tallest ranges, also in the aster family, a few yarrows with their lacy foliage and clustered white blooms may be present.

Autumn may not be a time to count on flowering plants here in the Sky Islands, but surely that very capricious quality renders them that much more special. A bit of tantalizing dessert to the main floral fare sprinkling the remainder of the year.

Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers a wide variety of private, custom-made courses, birding & biodiversity tours. Visit ravensnatureschool.org