Here at the botanical garden in San Francisco we have numerous clones of Dahlia imperialis, most wild colllected from southern Mexico and Guatamala. Some have flowers to 5 inches across. One clone blooms early (a few weeks prior to Thanksgiving ) while most bloom closer to Christmas. They come from white to pink to dark lavender and there are double and single forms of most. Some have reached to 18 feet tall.. When crossed they produce lots of viable seed and some interesting (shorter, stockier) forms are being developed. We also have two more everblooming species. Dahlia tenuicaulis hails from Chiapas, Mexico and blooms May through February It has two inch mid lavender flowers and only gets 8 to 10 feet tall. Dahlia sp. nova has thin half inches stems and leans through other plants to 10 feet and blooms April to March with large 4 inch pink flowers that hang downwards. It has smaller leaves. Some of the hybrids being developed seem to be everblooming. Don Mahoney San Francisco Bot garden at Strybing Arboretum