The selection of a seed-bearing variety of Cosmos atrosanguineus (Hook.) Voss

The southern highlands of Mexico are home to a wild ‘dahlia’, a perennial cosmos, Cosmos atrosanguineus. It reaches 60 cm with dark stems and narrow leaves and has tuberous roots. The flowers are deep blood red to dark brown with a scent very like chocolate. C. atrosanguineus was described, with a coloured illustration, by William Hooker in Curtis’ Botanical Magazine (1861). The species was introduced to cultivation in Europe and was widely acclaimed (it won a Royal Horticultural Society Award of Merit in 1938). In the meantime, the species was believed to have become extinct in the wild. The plant was initially maintained in cultivation either by seed or vegetatively. Over time, the seed forming character was lost. This loss was unfortunate since in temperate climates the tubers are at risk from frosts if left in the ground during winter. It is also expensive to reproduce the plant vegetatively. Between 1990 and 1995, we selected from rare seeds, plants that closely resembled the early illustrations. This cultivar, under the name ‘Pinot Noir’, was submitted for Plant Variety Rights protection in New Zealand and Europe. It was granted in 1997. This fertile seed-raised cultivar has been maintained for more than 20 years and created a population of C. atrosanguineus bred from seed and which retained genetic diversity. C. atrosanguineus ‘Pinot Noir’ has since been the source of multiple new selections. It now appears that C. atrosanguineus is not extinct in the wild, with records of the plant from 1986 through to the recent collections of Aarón Rodríguez.