

        Snakes and Stars--/Monadenium/

        Though they lack the diversity of species, the breadth of
        distribution, and the popularity in cultivation of their cousin
        genus, Euphorbia, the several dozen species of Monadenium have
        attractions of their own for anyone who enjoys succulent plants.
        Restricted to Africa, monadeniums occupy an approximately "J"
        shaped arc of territory that starts in Somalia and Ethiopia,
        sweeps through Kenya and Tanzania (their center of
        distribution), and reaches as far south as northern South Africa
        before turning west through Botswana and Angola. Most of their
        habitat, though dry, is tropical in temperature, lacking the
        extremes of cold and utter aridity that mark the domains of some
        of the most specialized forms of succulent plants.

        The key difference between /Monadenium/ and /Euphorbia/ lies in
        their respective inflorescences, with the simple, euphorbia-like
        flowers of /Monadenium/ partly hiding from view in a sort of
        cupping hood made of bracts and called an involucre. Some
        monadeniums have multiple involucres and in some the hoods flare
        out dramatically or become brilliantly colored, red or pink, but
        not many people would grow the plants solely because of their
        inflorescences. Instead, it's the range of odd shape and growth
        forms that monadeniums exhibit that provide their appeal.

        To a certain degree monadeniums can duplicate the tremendous
        range of forms attained by the succulent euphorbias. In their
        most basic form, found in the small growing Monadenium
        invenustum, or the taller M. arborescens, monadeniums consist of
        one or more somewhat succulent stems (about pencil-thick in the
        smaller plants), with slightly succulent leaves that grow out of
        barely raised, sometimes spiraling, stem divisions. These stems
        and their usually deciduous leaves arise from a large, tuberous
        root. Regardless of their low level of overall morphological
        modification, these species have the complete array of
        flower-with-involucre that defines the genus.

        The various groups of more specialized monadeniums have
        elaborated on these basic themes of succulent stems, tuberous
        roots, and, in the most typical species, stems organized into
        patterns of raised tubercles. These most typical plants (largely
        Kenyan and Tanzanian) make up a series of species in which the
        stems steadily become thicker and more succulent and the
        markings become more identifiable as increasingly prominent
        tubercles. Monadenium rhizophorum, for example, still has
        relatively thin stems, divided but not entirely covered by
        elliptical, spineless tubercules, while in M. lugardae the stems
        have thickened to an inch across, grow largely upright and are
        arranged into patterns of diamond shaped tubercules. In
        Monadenium heteropodum and M. guentheri the tubercles stand out
        boldly and come armed with small spines at their apices.
        Monadenium ritchie has dome-shaped rather than pointed
        tubercules and in M. schubei the tubercules are so pointed that
        the plant seems to bristle with spines, even though the actual
        spines at the tubercule tips are small and harmless.

        When mature these monadeniums grow into dense clusters of
        sinuously bending stems that emerge from a tuberous base, like a
        colony of twisting, light-green snakes. Their persistent obovate
        or spatulate leaves and almost tubular involucres grow from the
        tips of the branches. In contrast, the rare, slow-growing
        Monadenium reflexum, from Ethiopia, has lost the dense branching
        habit and the tuberous base, as well as the persistent leaves.
        Its very long, reflexed tubercles point downward and give it a
        shaggy-looking appearance, and its foot tall, three inch wide
        main stem may have a couple of upward pointing branches, the
        whole effect of a mature plant somehow resembling a humanoid
        cartoon creature.

        Instead of dense, precisely patterned tubercles covering their
        stems, a second group of monadeniums has developed stems
        scattered with prominent leaf bases ending in a cluster of small
        spines shaped like a star or sunburst. Monadenium stellatum, a
        rare species from Somalia with a longitudinally grooved wooden
        stem, has spiked leaf bases four times longer than thick, while
        in M. magnifica and its thicker-stemmed near relation M.
        spectabile, the leaf bases are lower, the starburst spines not
        as obvious, but the succulent, long-lasting apical leaves
        themselves come armed with decorative spines along their keeled
        midribs.

        In other monadeniums the stems have become reduced, even
        deciduous, and the tuberous base has taken on more importance.
        These geophytic plants, with only underground parts much of the
        year, include species such as Monadenium majus, from dry parts
        of Ethiopia, and several species from unlikely habitats such as
        Angola, areas sharply divided seasonally between wet and dry.
        Some of these largely underground monadeniums have dramatically
        flaring involucres, with unusual patterns and markings.

        In still another variation, Monadenium ellenbeckii, from
        Ethiopia and Somalia, consists of a cluster of small, succulent
        stems that emerge from a central base, but instead of spines or
        tubercles its branches are covered with a velvety, kelly-green
        epidermis that looks like corduroy.

        On the whole monadeniums adapt to cultivation without much
        difficulty. Many won't ever outgrow a five or six inch pot, and
        they respond to bright light and warm temperatures. Generally,
        any quick-draining succulent soil mix will suit them, and the
        snake-branched or star-spined ones will do well with water about
        once a week in the warmer months, and every three weeks or so in
        winter (when they should be protected from cold). The dwarf
        plants with tuberous roots, especially the geophytic species,
        need to be kept drier in winter, and whenever they're not
        growing actively, although raising the tuberous base above the
        soil line will ease the danger of rot. The more "primitive"
        species are easy to grow in spite of their tuberous roots, and
        they can be watered a little more frequently in winter, or given
        a little less light than the others without much worry.

        Nothing else really looks much like a Monadenium, and in recent
        years they have both become more available and more popular
        among succulent growers. The Garden has a good collection of
        Monadenium, and we propagate a few extra ones for sale from time
        to time.

        -Fred Dortort


        Fred Dortort has grown cacti and succulent plants for thirty
        years. He's studied and observed plants in Baja California,
        mainland Mexico, South Africa, Namibia and the American
        southwest. He's lectured widely on succulent plants, has taught
        classes at the Botanical Garden, and written numerous articles
        for the /Cactus and Succulent Journal/, as well as publications
        such as /Pacific Horticulture/ and /Garden/.

        Fred is a Garden Volunteer. We appreciate his time and
        knowledge, working with the succulent and cactus collection
        (Arid House <../collections/collections.shtml>) and helping with
        propagation for our Plant Sales <../plantSale/PlantSale.shtml>.



