The shaded understory of the Mesoamerican Cloud Forest is brightened this month by the electric purple flower heads of Bartlettina sordida, commonly known as bartlettina or purple torch. This large tree daisy has been grown at the San Francisco Botanical Garden since 1988, originating from a seed collection made by Dr. Dennis Breedlove in Oaxaca, Mexico. Bartlettina sordida is a member of the daisy family Asteraceae, a large plant family that contains many familiar plants such as dandelions and sunflowers. While many of its close relatives measure only inches tall in height, B. sordida towers above them-and you-reaching heights of up to 8 to 10 feet. Most of the other tree daisies in the garden's collection bloom primarily in the fall. However, Bartlettina sordida's striking flower display is produced throughout the spring as well, making it a show stopping beauty many times of the year.
The peculiar flowers are not individual flowers, but rather clusters of many flowers. Typically, a daisy has two types of flowers that make up its inflorescence: ray flowers which mimic petals and disc flowers which make up the center. Bartlettina sordida lacks ray flowers, giving its inflorescences a puffy, petal-less appearance. The flowers are a favorite of pollinators in the garden and bloom just in time to serve as a popular meal for the pipevine swallowtails. Lean in to smell the fragrant flowers and catch the mild perfume resembling lilac and honey.
Cloud forests, which are named for the perpetual moisture that rises from humid lowlands and condenses into fog at higher elevations, are rich centers of plant biodiversity that particularly under threat from human encroachment and climate change. Thanks to San Francisco's wet winters and the summer fog, the San Francisco Botanical Garden is uniquely situated to grow the unusual flora from the cloud forests of Mexico and help preserve and protect some of its stunning biodiversity.
Bartlettina sordida will thrive in any garden with bright shade and rich moist soil. No pest or disease problems have been noted on this vigorous plant. It is, however, frost tender below 25 °F. It is easy to grow and propagate, but like many plants in Asteraceae, Bartlettina sordida is known to become weedy in habitats with ample moisture.
IN BLOOM CONTRIBUTORS: Text and profile by Sarah Callan. Photos by Joanne Taylor and Mona Bourell.