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Species Spotlight

The Baccharis Tribe

By Doug Moore

As birding proved a bit slow on my Whitehouse walk for the International Migratory Bird Day, the group focused mainly on the abundant wildflowers and plant diversity. Just off-trail below the bat houses, Nancy Zierenberg of the Arizona Native Plant Society noticed a curious little shrub with thin, asymmetrical leaves, and packed with hundreds of just-ready-to-pop flower buds. Taking a piece home, “Z” later e-mailed that she thought the shrub was Yerba-de-pasmo, Baccharis pteronioides. Her ID was confirmed when I returned to the spot a few days later to take photos and found the plant in full bloom. Its dozens of distinguishing small, creamy-white flowers were swarming with butterflies, solitary bees and other pollinators!

Yerba-de pasmo, “herb of astonishment or wonder” in English, is in the composite, or sunflower, family. It is a small member (max. 3’ x 3’) of the genus Baccharis, which also includes Seep Willow and the infamous Desert Broom. In fact, there are six species of this genus in the Santa Rita Mountains, of which at least Desert Broom (B. sarothroides), Seep Willow (B. saliciflolia), and Yerba-de pasmo grow in Madera Canyon. Plants of this genus are dioecious, meaning that the sexes are separate- male plants produce male flowers and female plants produce female flowers. Each “flower” of a composite plant is actually an aggregation of tiny individual blossoms. Typically no larger than the head of a thumbtack and white to cream-colored, Baccharis blooms are made up entirely of disc flowers and contain none of the petal-like ray flowers seen in more typical daisies and sunflowers. Though small, these flowers often appear irresistible to insects; a glance at a flowering Baccharis will often provide an excellent cross-section of the pollinators currently out and about. All members of the genus have traditional medicinal uses; infusions of Yerba-de-pasmo leaves were used for “chills”.

Mere mention of Desert Broom often elicits gasps of horror and outrage from gardeners and allergy sufferers. Though a true native plant, Desert Broom loves disturbed soils and is invasive along roadways, housing developments and agricultural land. In the fall, legions of silk-tasseled seeds blow about in “desert snow” believed to add to plant-part allergies. None-the-less, due to hardiness and the amazing attractiveness of their flowers to insects, Desert Willow and other Baccharis relatives make excellent landscape plants! The trick is to grow only male plants, as it is the females that produce seeds and the mess. When the plants start to flower, it is easy to distinguish the male flowers with pollen; propagate a male plant or two and quickly pull all the rest!

In Madera Canyon, Yerba-de Pasmo blooms from April-Sept. A nice patch of Seep Willow, the most water-loving member of the tribe, can be found on either side of the Proctor Road crossing of Madera Creek and blooms August-September. Desert Broom grows along the road up to the canyon and at the intersection of the Proctor Loop and Proctor Road; it blooms September-November. If you want to see beautiful hairstreak, blue and queen butterflies, as well as discover a host of other interesting insect pollinators, seek out a flowering Baccharis! Even “weeds” can have redeeming qualities!