Dahlia rupicola

 

Dahlia rupicola Sørensen (1969) is known from western Durango and eastern Sinaloa along the state line with Durango at elevations of about 1800-2300 meters (6,000-7,500 feet). It inhabits sunny rock ledges, sometimes on cliff facings high above the highway. Associates include species of Agave, begonias, mosses, ferns, and sometimes D. coccinea. Its finely dissected leaves give it a beautiful ferny appearance.

 

Canes are perennial from thickened rhizomes, and most are 0.4-1.8 m (1.3-5.9’) tall. The multi-stemmed plants are often erect but sometimes hang down along the rock face (DES, personal observation). New stems are green and glaucous; older growth is somewhat brittle, tan, glabrous, and with prominent lenticels. Leaves are opposite along the stem, thrice compound, and frequently have dissected stipels at the lowest rachis nodes. Flower heads are about 8-9 cm (3.1-3.5”) across; ligules are pale lavender with a yellow spot at the base, disc florets are yellow. Flowering occurs during August and September, but may begin in July during some growing seasons (DES, personal observations). There are 34 chromosomes per cell (n=17).

 

 

 

 

 

 

References

 

Saar, D. E. 1999. A phylogenetic analysis of the genus Dahlia (Asteraceae): an interdisciplinary study. Ph.D. dissertation, Department of Biological Sciences, Northern Illinois University, DeKalb, IL, USA, 266pp.

 

Sørensen, P. D. 1969. Revision of the genus Dahlia (Compositae, Heliantheae-Coreopsidinae). Rhodora 71: 309-365, 367-416.