Adenium crispum x "obesum" hybrids
This hybrid line was a huge breakthrough in adenium breeding. There were a few such crosses in the early 1990s in California and possibly elsewhere, but even though the F1 plants had the petal markings of crispum, the usually small, twisted flowers didn’t inspire much enthusiasm. In 1999 I sent a cutting of A. crispum to a collector in Taiwan (I later named it ‘Famous Ancestor’. He propagated it and shared it with other growers. This species is difficult in hot, humid climates. The clone died out within a couple of years, but not before hybrids were made with A. “obesum”.
First generation (F1) hybrids inherit from "obesum" vigorous vegetative growth and large, colorful flowers. The crispum parent often contributes a substantial caudex, and quilled flowers with strong nectar guides that extend to the petal tips. Unfortunately, both parents tend to contribute weak stems. Plants of this line are usually slow-growing, taking at least 5 years to develop their character (in Arizona; they grow much faster in more tropical climates).
After several generations the Taiwanese breeders had eliminated the quilled petals and created plants with large flat flowers exhibiting bold petal markings. The nectar guides on the petals often morph into bold blotches and stripes. All flowers with such petal markings are descended from A. crispum, and probably from 'Famous Ancestor'. By 2008 there were millions of plants and hundreds of stunning named cultivars all over Asia. The plants in this group are mostly small to medium-sized and slow-growing, with modest caudexes (about 2 feet [61 cm] tall and wide); but some are “obesum”-sized (3 to 4 feet [91-122 cm]). Only the best clones have sturdy stems; most need pruning every few years to maintain a neat form. Superior clones flower profusely throughout the warm season. Both parent species are very cold-sensitive, but many of the complex hybrids (second generation and beyond) are resilient as long as they’re kept dry during winter.
Almost all cultivars on the market are grafted. See the superior cultivars page for a big gallery of these hybrids.
Adenium 'Harry Potter' was the first crispum-"obesum" hybrid with fairly flat petals and bold markings. The nectar guides have become blotchy stripes. It was created in Taiwan by C.F. Chang in 2003, only 4 years after the introduction of A. crispum. A first-day flower is at left; a week-old flower at right.
A few more early crispum-"obesum" cultivars. Left: Adenium 'City' from Taiwan is an example of a flower with strong contrast between the background and the nectar guides.
Below: New and older flowers of 'Star of Taiwan'
Below: 'Classical' has bold blotches overlain by even bolder lines. Created by H.C. Chen.