§ Arizona-Sonora Desert Museum
© No reproduction without consent of the author

The purpose of hybridizing plants is to combine desirable characteristics from different individuals to produce superior forms, with the definition of "superior" being mostly the breeder's opinion. My goals for adeniums are a sturdy growth-form with a large caudex or trunk, vigor manifested as fast growth and disease resistance, such intense flower colors as blood-red and sharply contrasting red/white picotees, and a long blooming season. Significant progress has been realized in only three generations.

Adenium Arizona

Adenium Arizona Group is the name I have given to a cultivar group of hybrids created by crossing Adenium obesum and Adenium swazicum.

The F1 progeny show a pattern:

  1. The plants exhibit hybrid vigor with fast growth, prolific flowering, and high resistance to root-rot. The last trait is apparently inherited from A.swazicum, which tolerates heavy, wet soils (Peckover, 1995).
  2. The stems are usually much sturdier than the floppy stems of Adenium swazicum. Neither parent species is distinctly caudiciform (at least among the plants in my collection) nor are the offspring. They do rapidly develop swollen roots and stems, however.
  3. The leaves are intermediate between those of the parents.
  4. Like the parents, hybrids lack an obligatory seasonal dormancy, tending to grow and flower continuously if kept warm and well-watered.
  5. Flower coloration resembles that of Adenium swazicum in being solid or fading only slightly toward the dark throat. The anther appendages are intermediate in length.
In short, this cultivar group tends to inherit the best qualities of both parents and exhibits hybrid vigor. When superior parents are used, the results are spectacular. Adenium obesum 'Red Ever-bloomer' has been used in all of my released Arizona crosses to date because of its upright stems, good red flower-color, and long blooming season.

Adenium swazicum 'Perpetual Pink' contributes sturdy stems, large flower size, long blooming season, and flower color from pale pink to deep raspberry red. When the deep purple A.swazicum 'Boyce Thompson' is used, the most noticeable difference is darker flower color ranging to blood- red. See Dimmitt and Hanson (1992) and Dimmitt for photographs of these plants.

Adenium 'Endless Sunset': Young plants have weak stems but become arborescent if grown hard and pruned until maturity. Flowers are 7.4 cm (2.9 inches) in diameter, solid deep pink. This clone is everblooming-it never stops flowering if grown under tropical conditions. At 15 years of age the trunk of the original seedling has dramatically thickened to halfway up its 2.1-meter (seven-foot) height. Cuttings grow vigorously and form massive roots quickly; stems thicken nicely in their third year. The parentage is A.obesum 'Red Everbloomer' X A.swazicum 'Perpetual Pink'.

Adenium 'Crimson Star': Stems are very sturdy and erect to ascending. Flowers are large (8.6 cm, 3.4 inches), solid, deep blood-red (Fig.26), and are borne nearly year round (Table 1). The plants often take only a month's rest in early spring, then resume growth and flowering. The parents are A.obesum 'Red Everbloomer' and A.swazicum 'Boyce Thompson'. This is the best adenium clone I have seen to date. In addition to the above qualities, cuttings root readily, grow rapidly, and begin to flower in four-inch pots. Roots and stems of cuttings thicken dramatically in the first year. Well-branched, nearly caudiciform shrubs or treelets four feet tall and wide can be produced in as little as three years (Fig.27). Plants continue flowering well through cool weather and almost never rot. It's only negative is that it is a very reluctant breeder, though it has parented a few offspring.

Adenium 'Red Ribbons': Stems are thin and weak, tending to droop under the weight of the large leaves unless pruned or grown in windy conditions that strengthen branches. Flowers are very large (10.9 cm, 4.3 inches), deep red with only slight fading toward center. The petals hang down like ribbons. The flowers are borne up to eleven months a year. It has the same parentage as 'Crimson Star'.

Adenium 'Volcanic Sunset': Stems are very sturdy and erect, with crowded leaves due to short internodes. Flowers are large (9.4 cm, 3.7 inches), deep red, fading slightly toward the throat. It blooms almost 12 months a year, usually profusely except during hottest weather. It has the same parents as 'Crimson Star'.

Adenium 'Asha': This is an Arizona back-crossed to A.obesum. It was created by Dr. Ashish Hansoti of Bombay, India, and named after his mother. Its outstanding characteristic is its huge, bright pink flowers. At 11.4cm (4.5 inches) across they surpass those of the previous champion, A.arabicum 'Singapore' (=A.obesum coetanum, Fig.28). The flowers are of good form, being very round in outline, and usually face upward or outward. It is nearly everblooming, taking only a few weeks' rest during the hottest part of summer. If temperatures remain below 100F (38C), it can bloom 12 months a year. Its thick, very fast-growing, yet weak, stems soon droop to the ground. Grafting onto a sturdier rootstock greatly improves the form, but frequent hard pruning is still needed to maintain an upright plant. It is an inferior parent: offspring so far have had disappointing flowers.

Other Hybrids

Adenium 'Crimson Picotee': (crosses between A.obesum and A.multiflorum tend to have large, evergreen leaves and very thick, sturdy stems. The flowers are like those of A. multiflorum but with a broad rather than narrow red border on the white petals. The clone 'Crimson Picotee' has moderate-sized (7.0 cm, 2.75 inches), ruffled flowers with a fairly distinct, broad border of blood-red (Fig.29). It blooms intermittently up to 8 months a year but never profusely. The parentage is A.obesum 'Red Everbloomer' by a mediocre clone of A.multiflorum; better plants of this grex are undoubtedly possible. It is a fertile breeder in both directions and tends to produce very robust offspring. None have yet flowered.

Continuing Selection

The horticultural potential of the genus Adenium has only begun to be developed. The best cultivars to date are shrubby succulents with long blooming seasons. Their flowers are richly colored in pink to red and bicolored red-white. Look forward to these further potentials:

  1. Plants with massive caudexes and brilliant, year-round flowers. Crossing the arborescent species with one of the existing superior-flowered cultivars should produce such plants. Unfortunately, my first two crosses between (a shrubby form) and 'Crimson Star' produced plants with nearly year-round dormancy and deformed flowers. Hopefully the solution is using other clones for parents.
  2. Plants more tolerant of cool conditions. Adenium swazicum tends to transmit this trait to its offspring.
  3. Plants with large, striped and spotted flowers. Those of A. somalense crispum are beautiful at close range; imagine such coloring on a four-inch flower.
  4. Other flower colors. The yellow throat of A.oleifolium might be expanded onto the petals. The red flower pigment can be expected to mutate to blue one of these days, as it has in many other red-flowered species. I once had an A.obesum with blue petal margins, but it died.
  5. Variegated foliage. Well, some people like it; I think such plants look sick and should be destroyed. Someone else will have to select these.
  6. Double flowers. See the first paragraph about what constitutes' "superior." I think most double flowers are ugly. Compare the misshapen abominations created in other plants such as gloxinia and hibiscus with the elegant symmetry of their single-flowered ancestors. (I'll acknowledge that some double roses have superb forms, but they are the products of more than a century of intensive selection.)

Fig.26. Flower of Adenium 'Crimson Star' (bottom) with parents A.obesum 'Red Everbloomer' and A.swazicum 'Boyce Thompson' (top)

Fig.27. Four-year-pld cutting of 'Crimson Star' in a 24-inch pot. Even faster growth is possible.

Fig.28. Flowers of Adenium 'Asha'. The topmost flower is one of 'Singapore', the previous size-champion

Fig.29. Flowers on a young plant of Adenium ' Crimson Picotee'. Flower size and sharp coloration decline in larger plants.

[Home] [Part 1] [Part 2] [Part 3] [Part 4] [Part 5] [Part 6] [Reference]