Dahlia spp. Photo by James Gaither.
You must look up high to see tree dahlias! They bloom at the top of slender 20-foot stems. The petals are up to six inches long and ray shaped, and can be found in shades of pink and purple with golden disc florets in their centers which physically define their lineage to the daisy family (Asteraceae). These lofty, exuberant tree dahlias originate in the cloud forests of Central and South America. Each spring they grow rapidly from underground tubers developing compound leaflets often 36-inches long. By late fall, they have reached 15 feet or more and are ready to bloom. There are 26 species of tree dahlias; they can be single or double, erect or drooping, rose- colored or white, depending on the species. The tree dahlias that thrive in the Mesoamerican Cloud Forest collection at the Garden are Dahlia imperialis and Dahlia tenuicaulis, both with lavender flowers and the 'Double White' cultivar.
Dahlias originated in the highlands of Mexico and were nurtured in the fabulous gardens of Montezuma, the Aztec king, whose civilization reached its peak in 1200 A.D. Cortez conquered the Aztecs in 1552 and brought many plants from Mexico including tree dahlias back to Spain for propagation. The Aztecs called tree dahlias "cocoxochitl" or "water pipes," because their 4-inch thick stems were hollow and used to transport water from the mountains to the lowlands. In our Nursery, Curator Don Mahoney propagates tree dahlias by planting 12-inch sections of these "pipes" with nodes, standing upright or lying flat in potting soil. In just nine months a stem can be ready to bloom. They are susceptible to wind, and grow best in forests where they are protected.
The Mesoamerican Cloud Forest garden blooms during our fall months when the majority of other plants in the Garden have gone dormant. Our mild seasons and abundant fog approximate similar conditions found in their high elevation tropical homelands.
||Prefers shade, moderate water and well drained soil
||Pink/purple to white flowers appear in the fall
||Great for areas that you want to have some growth and color within a year from planting. Best when planted with other shrubs and trees for protection from wind
||The dahlia is the official flower of San Francisco; for a breathtaking display of other species and cultivated dahlias, check out the dahlia display on the east side of the Conservatory of Flowers
IN BLOOM CONTRIBUTORS:
Text by Kathy McNeil. Photos by Joanne Taylor. Profile by David Kruse-Pickler.