Stapelia gigantea, the "Starfish Flower" - Cactus Club

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Stapelia gigantea, the "Starfish Flower"

Plant of the Month > Species Q to S

by Bruce Brethauer

     While working at the Society’s booth at the "Affair of the Hort" several years ago, I noticed that a good number of youth showed interest in growing cacti and other succulents. I was curious about which plants caught their eyes as they examined our sales table, and where necessary, I tried to redirect their interests to plants which I deemed more suitable to novice growers. Sometimes I suggested plants which I thought would hold the interest of young growers long beyond the end of the day: few people could maintain an interest in a plant which may only produce one or two new leaves each year. To really hold the interest of a young grower, a succulent needs to do a bit more than just look a bit strange.

      One good choice for young growers (and mature growers who can appreciate some of nature’s more unusual creations) is Stapelia gigantea, the so called "Carrion Flower". Not only is it an easy and highly adaptable plant, well suited to a sunny site by the window, it also has several traits which tend to make it particularly appealing to young growers. The plants are fast growers, producing multi branched succulent stems. These are covered with a very fine layer of felt-like fibers and are entirely free of spines, so there is no possibility of injury from handling these plants. These stems initially grow upright, but as they grow, they are unable to support their own weight, and will tend to become more scrambling, with only the stem tips growing upright (seldom growing taller than about 8 inches, but potentially spreading to several feet or more across when grown in the open ground). The stems are four angled with 4 sharp ribs which bear regular "notches" (the nodes with vestigial remnants of leaves), and 4 very deep grooves between the ribs - in cross section, the stems look like a thick plus sign.

      Plants of the "Carrion Flower" may bear a superficial resemblance to some cacti, but they actually belong to the milkweed family (the Asclepidaceae): admittedly, these may not look very much like the familiar milkweed, but when this species produces fruits and seed, it pods look very similar to those of the milkweed, and its seed bear the characteristic silken "parachutes" as well. Without getting too bogged down in botanical details, its flowers also fit the basic template for other members of the milkweed family.

   The trait which most distinguishes this species are its immense flowers, which may open to a diameter of 10 to 12 inches. The flowers bear 5 broadly triangular petals which are fused together at their base, the petal tips taper abruptly to a very narrow, almost filament-like point. Unlike our domestic milkweeds which are typically pollinated by butterflies, bees and wasps, and which generally produce a very sweet fragrance to attract these insects, the flowers of Stapelia gigantea (as well as most of the other succulent members of the greater milkweed family) are pollinated by flies, and so, these flowers liberate a scent which will attract these in huge numbers: in short, these flowers are FOUL SCENTED, typically producing the scent of rotting meat (accounting for one of the common names of this plant, the "Carrion Flower"). Not only do the flowers smell like rotting flesh, but their petals are covered with long hair-like fibers, and the petals themselves have the feel of leather, having roughly the same texture as fine suede, or chamois to mimic the appearance and feel of animal skin. The flowers are curiously marked with a series of fine lined broken concentric circles in maroon against a buff background, the maroon markings become more closely spaced towards the center of the flower, and in most plants, the maroon coloration may predominate in this region. The flowers are remarkable for their size, hair-like fibers and unusual markings, but I would stop short of calling them beautiful (I’m sure that other growers would give me an argument, but to my eye, these flowers are strikingly odd and quite fascinating in their own right - but not beautiful). The structure of the reproductive parts of the flowers (which mostly lie out of sight beneath the huge petals, and the pseudo-anthers) is remarkably complex, and will only admit insects of a very specific size. In spite of numerous attempts to facilitate pollination in my plants, these have never set seed for me, so I suspect that plants of this species may be very resistant to self pollination, and that our domestic house and bluebottle flies are not the proper size to pollinate their flowers. The plants typically produce their remarkable flowers in the fall, initiating their buds in response to the shortening daylight hours (if you grow these plants under lights, you will need to reduce the amount of time that the lights are on to initiate the formation of its flower buds). Oftentimes, these plants will begin to flower at about the same time that our first frosts occur, so moving the plants outdoors when they are in flower may not be a realistic option if you wish to keep them alive (a hard frost will kill this plant outright). If you really cannot stand being in the same room with these plants when they are in bloom, the flowers can be cut off, and thrown away (outdoors). The plant (sans flowers) has no noticeable odor, and snipping off the flowers should have no adverse effects. One curious trait of the succulent members of the of the milkweed family (this species included) is that they do not like to be moved when they begin to set their buds; any change in the angle that the sun strikes the plant may cause it to abort its buds and flowers. Most experts will advise that a plant should not be moved when its buds are being developed.

   Plants of Stapelia gigantea are easy to grow, and where they are happy, will produce remarkable growth, easily doubling (or even tripling) in size in a single year - plants require bright light, a very free draining (yet fertile) potting medium, and warm temperatures to produce its best growth. It grows well with my basic guidelines for growing succulents, but because of its comparatively rapid growth rate, it may also require more frequent fertilization than most other succulents. During its growing period, it will also require frequent watering - while the potting medium should be allowed to go dry between waterings, this plant should not be subjected to extended drought from late spring through early fall.

     Plants of Stapelia gigantea are remarkably easy to grow from cuttings. Cuttings are best taken during the growing season (from spring through fall), but I generally recommend that cuttings be taken in spring so that they will have an opportunity to produce significant growth before the onset of cooler weather in fall. Set the cuttings aside in a warm spot that is not exposed to direct sunlight for about a week or two to allow the cut end to heal. Following this, insert a portion of the stem into moistened soil. In some instances, the stems will already have begun to produce the "buds" for new roots during the week or two of "healing", otherwise, these stems will probably begin to root within a week or two. Growth is rapid, and a small cutting can easily grow to flowering sized in 18 months or less (sometimes significantly less). Established plants will soon fill a very large pot, with many stems spilling over the sides of the pot.

   While I am generally very enthusiastic about this species, it is not without a couple of important concerns. First of all, many of the other members of the greater milkweed family produce toxins, and while I am uncertain if this species also produces toxins, in those households with pets and particularly young children, parents my may wisely choose not to grow this plant, unless they can keep it beyond the reach of curious hands and paws. The plants of this species seem to be ambrosia to mealy bugs, so they should be frequently inspected for these pests lest other plants in your collection become infested when mealybug offspring start to migrate. This is one of the few plants on which I have seen an infestation of one of the root mealybug species. These pests attack the roots of  plants, sapping their strength, and in extreme infestations will kill the plant outright: their presence can only be confirmed when repotting the plant, when the roots can be exposed and inspected, so I recommend that these plants be repotted at least once a year, if for no other reason than to provide an opportunity to inspect the roots annually.

   These concerns aside, I find Stapelia gigantea to be one of the most interesting members of the milkweed family, It is a comparatively fast growing plant, producing a numerous succulent stems which are spineless and covered with a felt-like fibers, its flowers are huge, and are striking for their curious markings, their hair-like fibers, and their strange trait of attracting flies for pollination. They are easy to grow, and are comparatively easy to bring into flower. Admittedly, these are not plants for all growers, but when I describe the curious traits of this plant to younger growers - particularly boys - this plant will generate considerable interest (much to the ire of their parents). It is one of a few succulents which generates interest in many young growers.

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