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Desert Roses and Half-Men -
Adenium and Pachypodium Part 2
The
first Pachypodium I saw
astonished me because of its bright silver color; not in leaf
or flower, but an entire spiny stem that looked like it had
been sprayed with silver paint.
In those days, outside of major institutional collections
(such as UCBG), all of these succulent members of the oleander
family (Apocynaceae) now considered by some to be part of an
expanded Asclepiadaceae) were rare as the proverbial hen's teeth,
and they certainly epitomized the exotic and fantastic to my
eyes. Now, even though much more common in cultivation,
pachypodiums and their close relatives in the genus Adenium
still must be included among
the most interesting and desirable of succulent plants.
These
succulent Apocynaceae range over many of the arid parts of Africa,
and have ventured as far as the southwestern tips of Arabia.
Pachypodium have diversified into a range of bizarre forms on the
huge island of Madagascar, a few hundred miles east of the African
continent. Adenium, in contrast, never made it to that island. They may have evolved after Madagascar
split off from Africa itself, millions of years ago.
In
any case, Adenium display
less diversity of form than their cousins. Most of the species live in the dry regions of eastern Africa,
from Somalia south to eastern South Africa; one species (A.
obesum ssp. boehmianum) grows as far west as the fringe of Namibia, and several
species can be found in Arabia and islands that lie between
the Arabian peninsula and the Horn of Africa such as Socotra.
Adenium
bear a certain resemblance to oleanders, non-succulent members
of the same family from the Mediterranean shores of North Africa.
Envision an oleander with somewhat leathery skin rather
than woody bark, with reduced leaves, and with an enormously
swollen base and you will have an idea of what an Adenium
looks like. The
species differ from one another in regard to the size and shape
of their base, whether the base is typically largely underground
or above ground, and the size and shape of leaves and flowers.
Small plants of Adenium, such as those typically found growing in containers,
generally resemble each other regardless of species. Some (A. socotranum) develop a swollen base more rapidly, some (such as A. arabicum
and A. multiflorum) branch more freely, some (A.obesum ssp. boehmianum) don't develop
much of a caudex at all.
If placed in a large container the differences between
species will become more obvious.
If seen in habitat (or photographs of habitat), the amazing
variety of surrealistic forms and exceptionally large sizes
attained by the various Adenium becomes slightly overwhelming. Some turn into trees, twelve or fifteen
feet tall and more and easily eight feet in diameter; some may
grow with their swollen bases flat on the soil, with skeletal
branches radiating out of them, a few leaves at the tips of
each branch during their growing season. Others look like heaps of boulders with
small trees growing out of their summit, or out of a single
boulder, in either case the ñbouldersî are the bases of the
plants. When grown to maturity, A. obesum, the most widely distributed species in the wild, may
be the most morphologically variable and fantastic, although
Adenium socotranum
(still rare in cultivation), with an absolutely enormous caudex
that begins to develop while the plants are still quite young,
certainly can provide competition for the choice of most interesting
member of the genus.
Along
with weird body shapes and strange habitats Adenium also have flowers; A. obesum has been called the desert rose because of its beautiful
flowers. Most species
will, if grown properly, bloom profusely, displaying masses
of usually red blossoms, sometimes red-tipped with white interiors. They are one of the few succulents to be grown for their flowers
alone in many parts of the world, and in the last decade or
so quite a bit has been accomplished in hybridization to increase
frequency and ease of flower production and intensify color.
Adenium,
though inhabiting some of the most arid parts of the world,
respond well to water in cultivation, and will thrive with frequent
waterings when they're actively growing, more than once a week,
perhaps several times a week in hot weather. When they go dormant, in late fall, they
drop their leaves and they should be kept very dry through the
winter, until the new growth starts in spring, with no more
than a light watering every month and a half or so or they may
promptly rot. They like heat, and in hotter and drier parts of Arizona they
will survive winter outdoors with some slight shelter. Our cloudy, humid winters are another
thing entirely, and most Adenium
won't survive outdoors in the Bay Area.
They need lots of light, but are not quite as fanatical
about it as many cacti and some other succulents.
They aren't too fussy about soil as long as it drains
quickly, and will benefit from a fairly rich mix as far as succulent
mixes go. Since Adenium are related to oleanders, eating them would definitely
be a very bad idea. Their
sap is toxic, but their epidermis doesn't puncture that easily,
and unless you have cats with very liberal ideas about what
constitutes potential food, I wouldn't be concerned about growing
them in a house.
We
have a number of different species of Adenium in the collection, and some of the recently developed
hybrids as well. We
are preparing a few for sale, but there is such interest in
flowering Adenium hybrids these days in places such as Florida and Arizona
that they probably will be showing up in retail nurseries here
before long.
(The
half-man and its relatives next month) |
