by Bruce Brethauer
Matelea (Gonolobus) cyclophylla is a vining plant which produces a remarkable corky caudex, reminiscent of those of the unrelated tortoiseshell plant, Dioscorea elephantipes. In the case of M. cyclophylla, the caudex can grow to upwards of 12 inches (30 cm) in diameter. The species is native to Mexico, and is frequently hailed as the only caudiciform member of the greater Milkweed family from the New World - at least, the only one which is familiar to succulent growers and aficionados.
This species is grown primarily for its remarkably textured, corky caudex: while Miles Anderson (of Miles to Go, and author of The World Encyclopedia of Cacti & Succulents), asserts that these can grow to a diameter or 12 inches (30cm), most of the plants which I have seen have a caudex which is much smaller - usually to about 3 inches (7.5cm). To be fair, I have only seen young plants in cultivation. The plant produces one or more vines which can grow to about 2 meters (just over 6 feet) in length. Pairs of opposite, heart-shaped leaves are produced in two ranks at the nodes. These leaves can grow to about 4 inches (10cm) in length. The leaves, and ultimately, the vines are deciduous, and are shed in response to cooler temperatures, drought, and possibly other stresses.
The flowers are smallish - approximately 1 inch (2.5 cm) across, with at least one flower being produced on each node on my plant. More curious than beautiful, the flowers have dull, very dark maroon (sometimes green) petals, with a central disk which is curiously patterned in more reddish, pink and whitish tones. The dullness of the petals is largely due to the presence of a very fine coating of "peach fuzz", this fuzz is at the threshold of my vision, but in the finely focused images here, are clearly defined. Images of the central disk reveal a remarkably complex structure; it is quite compact, barely 1/4 inch (6 to 7mm) across, and elevated no more than 2mm above the surface of the petals. This area features the pollinia, and the receptive stigmatic slits. Pollination is achieved when the pollinia are properly inserted into the stigmatic slits - even at the magnification in this image, these features are barely discernable. In nature, flies (presumably smaller species than our typical house, and bluebottle flies) are responsible for pollinating these flowers. Flowers can be pollinated by hand with the assistance of a microscope and micromanipulators. The flowers are produced at the nodes, close to the stem, and are often at least partially hidden beneath the foliage. An occasional glimpse under the leaves in summer may reveal otherwise hidden flowers. The flowers emit a scent of carrion - not as intense as the scent of many Stapelias, but still, it can be noticeable at close range - other sources suggest that some flowers are more strongly scented than those of my plant. Following pollination, fruits develop - according to Miles Anderson, only a single pod will develop following pollination (unlike other members of the Milkweed family, which typically produce 2 pods). Curiously, the pods will not open to release their seed until the following growing season - apparently, even after the deciduous vines have been shed. According to my resources, plants are only propagated from seed: although, I suspect that it may (perhaps) be possible to root cutting of the vines, but these would never produce the characteristic caudex so sought by most growers.
This species observes a strict and extended winter dormancy: the cool temperatures and shortened daylength of Autumn will initiate its winter dormancy, however, other environmental stresses such as drought, and extremely high temperatures may also induce dormancy at other times. The leaves are deciduous, and so are the vines, so the loss of leaves and vines at this time should not be regarded as cause for alarm. The period of winter dormancy is extended - typically lasting 5 months and possibly longer. During this time, the plant should be kept cooler, and dry, with only enough water to prevent root loss. Light levels at this time are not critical, and the potted caudex can be maintained practically anywhere which is dry and cool. This plant will not tolerate freezing temperatures, and extended cold is probably detrimental as well. This period of dormancy usually ends in spring when night temperatures regularly exceed 65 degrees. At this time, new vines grow from the apex of the caudex. I am convinced that this plant really benefits from high temperatures during its growing season, and that plants which are maintained year round at "room temperature" will never produce much annual growth, and are much less likely to flower.
This is an easy plant to grow and flower in cultivation; it responds well to my general guidelines on growing succulents, with a few considerations. Plants grown indoors should be provided with as much light as possible - more is better: I recommend moving this plant outdoors during the warmer months of summer to benefit from sun, rain and warm temperatures; you can expect better and faster growth, and a good production of flowers under these conditions. Here in Ohio, it tolerates maximum exposure to daylight, and even in the desert southwest, this plant will tolerate full sun and extreme heat - provided that it receives adequate moisture to maintain its foliage. Given regular watering, and monthly applications of dilute fertilizer through the growing season, its growth rate is good, and its caudex will increase noticeably. According to Miles Anderson, best growth is achieved when the plants are bedded out in the open ground in the garden. Given a rich, organic, fertile soil, even moisture (never soggy), summer heat, and lots of sunshine, this plant will grow remarkably well, and its caudex will increase significantly. When the plant shows signs of dormancy in the fall, it can be dug up from the garden, potted up and brought indoors to over-winter.
I have found Matelea (Gonolobus) cyclophylla to be easy, pest and disease free; its deciduous leaves and vines makes it unlikely to carry-over any pests or their eggs from one season to another. The caudex, with its thick corky layer is virtually immune to insect pests, however, these should be inspected in fall, as the crevasses in the cork could provide hiding places for some pests. It is an interesting plant, with curious flowers which reveal a remarkable complexity on very close examination. I am especially drawn to the distinctive corky caudex, which is comparable to those of Dioscorea elephantipes. I have grown both species, and have found M. cyclophylla to be easier to maintain, with more compact, less rampant growth. I have had some difficulty maintaining Dioscorea for more than a few years, but by contrast, I have never lost a plant of M. cyclophylla. Another distinction is that this plant will flower at a very young age - 1 year old seedlings can produce flowers, while plants of Dioscorea elephantipes appear to require some level of maturation before flowering. Even so, this is not a plant for every grower - the vines of this plant can and will grow to about 2 meters, requiring some form of support, and other growers will not be interested in a plant which lies dormant for nearly half of the year. For those persons with a special interest in the greater milkweed family, or plants which produce a caudex, this plant is well worth consideration.