Dorstenia sp. aff. foetidia - Cactus Club

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Dorstenia sp. aff. foetidia

Plant of the Month > Species C to D
 
 

       by Bruce Brethauer


   The Dorstenias are a unique group of generally smallish, perennial, herbaceous, or shrubby plants belonging to the Moraceae, or Fig Family. The genus is widespread, occurring in northeast Africa, the Arabian peninsula, Madagascar, and Central and South America. According to online sources, approximately 105 species are presently recognized - although older references have indicated as many as 170 species had once been recognized. The majority of the species are non-succulent, but a number of species are succulent, - either producing a tuber-like rhizome, or a succulent caudex. The genus is characterized by its distinctive inflorescence: many minute (often microscopic) flowers are produced on a fleshy receptacle. Depending upon the species and variety, the inflorescence may be flat, cupped or irregular, with long, fleshy bracts radiating outwards from its center. Virtually all the species are monecious, with each receptacle producing both male and female flowers; Dorstenia lavrani is one of the few (or perhaps the only) species which is dioecious, producing male and female flowers on different plants. Following pollination, seeds develop just beneath the surface of the receptacle, and rupture through to the receptacle surface as they ripen. When ripe, the seeds are forcibly ejected  from the plant and may travel many feet from the parent plant.



     Only a handful of the succulent species have been in regular cultivation, and several of these (including Dorstenia gigas, D. gypsophila, and D. lavrani ) are still comparatively uncommon in the trade and command fairly high prices. This is not the case with Dorstenia foetidia, which has been widely available (through mail-order nurseries and Cactus and Succulent Society sales) for decades, and is usually offered at very reasonable prices. It is one of the easiest of the succulent Dorstenias to grow and propagate. Young plants have a nice, squat appearance: The caudex is a translucent green, mottled with small paler green splotches, and prominently marked with brownish - grey leaf scars. Typically the stems of this species are unbranched at this stage, but the illustrated plant shows the beginnings of multiple stems - to my eye, the young plants have the appearance of a mostly melted green candle stub with leaves. The growth rate at this stage is fairly rapid, I have seen plants grow from tiny seedlings, less than an inch from leaf tip to leaf tip to flowering sized adolescents in less than a year. Younger plants seem to produce a succession of inflorescences over a fairly long period, while more mature plants have tended to produce fewer "flowers" over a shorter period of time. The inflorescences on my plants are small, often less than an inch across (including the fleshy bracts). The male flowers appear to produce a single minute filament topped with a tiny anther (the anthers appear as tiny yellow spots on my photographs). The greater portion of the female flowers are imbedded within the receptacle, with only the minute, hair-like styles protruding above the surface of the receptacle. As the plant matures, the stems develop an opaque grey "bark". At this stage, growth slows considerably, with the primary stems growing a little taller each year. Ultimately, this species may attain a height of about 12 inches, but my plant is approximately 6 inches in height after about 8 years of growth in my care. The leaves are non-succulent, with barely crisped margins on my plants, but the leaves are highly variable in this species, and may be narrower, or more crisped in plants from other sites. In years past, some nurseries offered plants identified as "Dorstenia crispa", and "Dorstenia lancifolia" based largely on the shape and degree of "crisping" on the margins of the leaves. Even at that time, these names seemed to be applied rather arbitrarily - so there was often confusion as to which "species" any plant belonged to. It appears that these plants have become more or less merged together in recent treatments, although some growers will still recognize varieties crispa or lancifolia based upon details of the leaf and region of origin. The original label on my plant was lost many years ago, I have a vague recollection that it was originally identified as D. crispa, but I have chosen to identify it as D. sp. aff. foetidia here. The species was named foetidia due to the fetid odor of its sap. This odor also appears to be fairly variable, and may vary in degree from plant to plant and due to genetics and differing growing conditions.



    This is a very easy plant to grow: it responds well to my general guidelines on growing cacti and other succulents, with a few modifications. First of all, I have found that this plant grows best under warm conditions throughout the year: it shows some stress when subjected to extended cold during its winter dormancy. While my plants have survived brief exposure to considerably colder temperatures (almost to freezing), they fare best when they are kept relatively warm in the winter - with temperatures dipping to about the upper 50's or the lower 60's during their dormancy. During their growing season, they fare best with temperatures ranging from the high 70's to the upper 80's - at higher temperatures this plant seems to produce less growth. Also, while this species seems to tolerate full sun, it seems to grow best when given dapple shade outdoors. (Indoors, it may fare better with full sun). Plants must be grown from seed, and while I have had some success in growing this plant from seed harvested from the receptacle and immediately surface sewn onto a gritty medium, it is far easier to harvest the "volunteer" seedlings from adjacent pots and re-pot these. While this species has the potential to become a nuisance (some of its tropical cousins are definitely weedy), I have never been overwhelmed with unwanted seedlings in my collection - I have little trouble in selling or trading the self sewn seedlings, so the appearance of a few stray seedlings is more serendipitous than annoying.



     All things considered, I am rather surprised that the Dorstenias are not more widely grown. For the most part they are easy plants to grow, tolerating a wide variety of growing conditions, and (in many species) tolerating somewhat lower light conditions than most succulents. The succulent species are generally smallish plants which produce an interesting caudex, attractively marked with white or paler green leaf scars, and topped with a short rosette of leaves which often produce nicely undulate margins. Many growers find Dorstenia "flowers" to be strangely attractive or odd to the point of being interesting, and grow these plants for these alone. In Dorstenia foetidia the "flowers" are generally produced either continuously, or in several successive waves over much of the growing season, which differs from the flowering habits of most other succulents, which generally produce flowers during a comparatively short blooming season. More often than not, if  is actively growing, chances are good that this plant will be producing "flowers". The small size of this species makes it suitable for windowsills, or growing under fluorescent lights. These plants do not produce spines (a real plus for those persons who may have pets and young children), however, many Dorstenias will produce a latex, which in some species, may be irritating or toxic. These plants have not found their way into the "Big Box" nurseries, and probably never will; they are available from mail order nurseries specializing in succulents, on E-bay, and from most cactus and succulent society sales. If you ever get an opportunity to grow this plant, give it a try.

 
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