The genus Dahlia comprises 37 species and is restricted to the highlands of Mexico. It ranks among the most important ornamental plants with more than 1000 varieties. As part of a project for the collection and conservation of genetic resources in the genus Dahlia, wild plant collections were conducted in cooperation with the Universidad Nacional Autónoma de México (UNAM) from 1999 to 2002. 23 of these species are in cultivation in the Hamburg Botanical Garden.

The genus Trillium, known as Waldlilien (wood lilies) in German, is characterized by its three conspicuous whorled bracts. They are mainly found in North America, although some species also occur in temperate Asia. Of the 50 currently accepted species, 25 are cultivated in the Hamburg Botanical Garden. The cultivation of many Trillium species is quite difficult, so that the sometimes large populations are a special feature.