Fockea edulis - Cactus Club

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Fockea edulis

Plant of the Month > Species E to F

By Bruce Brethauer

     Fockea edulis is one of  the more unusual and distinctive species of the Asclepidaceae, or the milkweed family, noted for its huge underground caudexes which can ultimately grow in excess of 21 inches in diameter, and tip the scales at over 100 lbs. The plants produce a branching tangle of vining stems, which in habitat, can exceed several meters in length. The growth of vines in some plants is said to become so rampant that it will eventually choke out the plants upon which they grow. Under cultivation, the growth rate of most plants is more modest, at least in my plants – with the vines adding about a foot or so of growth each year. The leaves are an attractive, dark glossy green coloration, and are oval to lance shaped, and are rather small, to about 1 to 2 inches in length and about 1 inch wide, although on my plants, these are smaller - to about half of the maximum size. In many plants, the leaf margins may be undulating, or “crisped”: plants with especially crisped leaves have been designated in the trade as Fockea crispa although it appears that most of the plants which are sold under this name are actually F. edulis.

      In habitat, this species is a true geophyte, with the majority of the plant, (a stem or root modified to store moisture and nutrients through drought and other environmental stresses), lying deep underground. In times of severe drought; both the leaves and vines are deciduous, leaving only a small stump above ground to mark the location of this plant. The underground caudex enables the plant to persist through extreme drought, sometimes surviving for several years without measurable rain. When the rains return, the plants will produce a flush of growth; in good years, adding a considerable growth of vines, and adding significantly to the weight and size of its underground caudex. In cultivation, many growers choose to reveal the huge caudex by lifting a good portion of it above the soil line when repotting. This is the best way to stage this plant, but whenever the caudex is exposed in this manner, the portions which are exposed virtually cease to grow - only the portion of the caudex which remains underground will continue to increase significantly in size. For this reason, it is advised to grow it for several years with the caudex buried in the soil, until it has attained a desired size before raising it above ground. The caudex is nicely textured with with a pebbly or warty surface, which may vary from a purplish brown coloration, but usually ages to a very pale brown/gray coloration.

      Fockea edulis is native to South Africa and southern Africa. Unusual for members of the asclepidaceae, or milkweed family, this species has the reputation of being edible (as indicated by its name “edulis”). It apparently served as an emergency food for the Hottentots who consumed the tubers after they had been specially processed to remove or neutralize any toxins that may be present in these plants.

     I have found this to be an easy and undemanding plant, tolerating benign neglect without complaint - it responds well to my general guidelines for growing succulent plants. I will add a few points specifically for this species - While Fockea edulis is less fussy about excess moisture than some of the caudiciforms and tuberous rooted succulents, it will nevertheless require a very freely draining potting medium which dries quickly. I have found that the product Moo-nure provides a surprisingly good potting medium for a number of my succulent plants - it has a fantastic texture which remains very friable, resisting compaction, while providing excellent drainage, and is good source of trace elements (I continue to rely on liquid fertilizer to provide adequate levels of nitrogen, potassium, and potash). I have recently begun experiments with this as a potting medium for some of my caudiciforms, and I am quite impressed with the results I have seen so far. Most authorities will insist that a medium which is so high in organic materials would not make a good medium for cacti and other succulents, but this has not been my experience, for those of you who are not entirely convinced, try mixing this product with your usual potting mix and see for yourself. Also, I cannot emphasize enough the need to grow these plants on the patio, once temperatures have become reasonably warm in the spring (this species will not tolerate frost). Only under exceptional conditions can a caudiciform be grown to perfection in home interiors. These plants really need a good exposure to sunlight (after they have been properly acclimatized), warm to hot summer temperatures, and exposure to summer rains, and regular fertilization through the summer months to produce their best growth. Anything less will probably result is such a slow rate of growth that most growers will give up on these plants. Also, it is best to provide a trellis or other support for the vines - while these may not be as rampant as those of other caudiciforms (members of the melon/cucumber family, and Cissus tuberosa for example), they will nevertheless benefit from some structural support. The vines may also be clipped to maintain a more compact plant, but this may limit the growth of the caudex.

      Even under the best of conditions, it will take at least a few years to produce an impressive caudex, and probably at least 7 years to produce truly huge caudexes: so this may not be a plant for those who demand instant gratification. Having said this, even a small plant with a modest sized caudex can be staged in a small bonsai pot and make quite an impression - I guess that it all depends on what you would consider to be big enough for your needs.

     In fall, when temperatures start to cool, bring this plant indoors for a long winter dormancy, during which it should be maintained at cooler temperatures and drier conditions. This plant will not tolerate frosts - light frosts will kill all foliage and vines, and a hard sustained frost will kill any portion of the plant below ground. The plant can be watered periodically through the dormancy period to limit any root losses and leaf drop. Under extreme drought, this plant will eventually drop all of its leaves and a good portion of its vines, but these will be quickly replaced in the spring when it resumes its growth.

     Over the years, this species has been regarded as one of the standards of the caudex producing succulents, indeed, many of the books on cacti and other succulents have treated this species as something of a “gateway” plant, the one generally recommended for beginners who are interested in starting a collection of caudex plants. I do not entirely share this view: on the one hand, this does appear to be a relatively easy plant to grow, presenting few challenges, and on these grounds, it is a reasonable choice for people who are new to growing caudex plants, but it also has a few drawbacks which may render it a less than a perfect match for many growers. Possibly the most significant issue is one of availability – In my decades of growing succulents, I have never seen this plant in any of the nurseries or garden centers – even ones with a better than average selection of cacti and other succulents: this will probably forever remain in the domain of the mail order nursery. Another consideration is that, under normal growing conditions, the greater portion of the caudex of this species, lies hidden from view: to produce a really impressive caudex in this plant, it is necessary to grow it for years, possibly many years, before raising it above the soil line – few growers (beginners or seasoned experts) have this kind of patience. And frankly, the portion of the plant which naturally grows above the soil line offers few enticements: by the standards of most growers, the flowers are quite small and pretty nondescript, and the leaves and vines do not compare well with those of other foliage plants – so for those years when this plant is growing its caudex invisibly below the soil line, the grower may be forgiven for relegating this plant to a more hidden spot at the back of the bench, lest they be asked to justify their interest in this plant before it has sufficiently matured.

           In my opinion, a better starter caudex plant would be one which produces the greater portion of its caudex above ground, and which produces large, brightly colored flowers; Pachypodiums and Adeniums for example, and while it may lack the colorful flowers, the ponytail palm also makes an excellent starter plant – and best of all, it is readily available from most nurseries.

     Even so, Fockea edulis remains one of the most popular and enduring of the caudex plants, and tops the lists of many growers as an ideal beginner plant for those becoming interested in growing caudiciforms. It is an easy species to grow, presenting few difficulties, and it is a plant with lots of character: by providing a few basic requirements, it is a reliable and long lived species, It may not be for every grower, but is seems once you have grown it for a while, you become hooked.

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