Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
I'm sort of having to invent a lot of names in writing this column! The reality is that there are many more plant species out there than there are names we have for them. This species is sometimes called a wild cotton, but the problem is, many other plant species have the same name, including many plants that are actually close relatives of the plant we get cotton from. True cotton, Gossypium herbaceum, is a member of the Malvaceae or Mallow family, and this family is very diverse here in Africa. A wild form of the cotton plant occurs here, and several relatives in the same family also produce cotton-like fluff pods. But the plant this article is about, Ipomoea albivenia, is not a member of the cotton family, but instead a member of the Convolvulaceae, the Morning Glory family, and a close relative of the sweet potato, Ipomoea batatas. It differs from the other plants called wild cotton in being a vigorous climber, which is why I decided to name it the climbing cotton! The scientific name Ipomoea means 'worm-like' and alludes to this and other related species' thin, climbing stems that worm their way into and up surrounding vegetation. The species name 'albivenia' means 'white-veined' and refers to the veiny, whitish undersides of the leaves. This species is also called a wooden rose creeper but I find that a clunky and not very descriptive name.
The Fast-growing Sun Stealer
In my own region, the far north of South Africa, this species is actually a common constituent of the dry savannah. And yet, I find that very few people know about it at all! It grows, most of the time, amidst trees and bushes, either in thickets in open savannah, or on rocky hills. In such places, it has plenty of surrounding vegetation that its trailing stems can scramble onto. It is in effect 'hitching a ride'. Most plants in regions where there is dense vegetation, must compete with surrounding plants for sunlight. The plants that can grow tallest the fastest, 'win' in the race for sunlight. Trees are the tallest of plants, but here in South Africa they rarely get very tall. In the savannah, the tallest trees are typically around 20'/6 m to 30'/9 m in height. Still, they are the tallest plants, and the 'winners' in the sunlight race. Once a tree has grown taller than its neighbours, it is set. Here in the savannah, these trees then typically stop growing taller and start growing broader. The most extreme examples are the umbrella thorn tree and a few other flat-crowned species. These trees grow amazingly broad, flat crowns. This enables them to hog the sunlight over a comparatively large area of the planet's surface.
And then you get the climbers, such as this one – which is one of the most vigorous climbers in the savannah. These wait for the trees to do it first. To get tall, a tree must grow a lot of wood tissue. It is no use being tall if the wind can easily blow you over or an animal can easily push you over. It takes many years for a tree to grow to 20'/6m in height. Not only must its trunk be sturdy, its root system must be too, to support the tall trunk as well as the spreading crown.
Climbers take advantage of all this hard work done by the tree. A young climbing plant pushes out a thin stem with a few leaves, and takes a while to gather a bit of sunlight and strengthen itself. The climbing cotton develops, early in its life, a thick tuber at the base of its stem. It also sends out fleshy roots. These store water and nutrients. This plant, like many other climbers, has quite large, broad leaves. These help the young plant to catch what light it can in the shade of surrounding plants. For a while the plant gathers nutrients, store them in the tuber, and fortifies itself. Then the scramble begins. Now the plant sends out long, thin, trailing stems in all directions. It is 'feeling' its way around itself. These trailing stems will seek sunlight. They will climb overlow, surrounding bushes, but when they find the trunk of a tree, they will realize they've struck the jackpot. The tendrils will now wrap around the trunk of the tree and lengthen very rapidly, heading up into the crown. The climber uses the strength of the tree trunk: its trailing stems are very thin since they don't have to support themselves. Because they are so thin, they don't require as much wood tissue – which is hard and costly in terms of material and energy for plants to build – and can lengthen much more rapidly. In a single year, one of these climbers can send its tendrils all the way up into a tree that is 20'/6m or more in height. And then they are out and above the canopy of the tree itself! There, the climber now makes lots of new leaves which spread out over the crown leaves of the tree. Thus the climber takes advantage of the tree's height and robs it of a portion of its sunlight!
Apart from that, though, these climbing plants don't harm their hosts. Their big, broad leaves never cover the entire crown of the tree, leaving it some of its own light. Sometimes the climbing cotton grows in open positions, with only grass, rocks and low shrubs around it. In such cases, it has to support itself, but luckily it then has enough room. It will form a low, spreading, mound-like shrub. Some of the stems will trail on the ground, but others will support each other.
Another advantage the climbing cotton gets from growing high into trees, is that it can display its flowers better. Like many members of the morning glory family, it has big, beautiful flowers. They are trumpet shaped and up to 10 cm/4" long and 8 cm/3.2" in diameter. They are creamy white, with crinkly petals, often with yellow or light pinkish inside the tubes. These big flowers are unfortunately not always easy for humans to see! Instead they're put where they can best attract pollinators. They are borne high up in the trees, and furthermore open mainly at night. But I've seen them open during the day on several occasions. They are fragrant and pollinated by moths and butterflies. I've also seen beetles inside them. These perhaps feed on the pollen or even munch on the flower itself; many of the flowers I've seen still open during the day were a tad eroded.
After the flowers (provided they've been pollinated) come those cotton balls! The fruit forms as a round capsule at the base of the flower. It develops over a fairly long period. The capsules finally open at the end of winter. They release the seeds, swaddled in these cotton balls! I think that these cotton-like fibres are a protection. The seeds are relatively large and contain a lot of nutrition, and some beetles, weevils to be precise, lay their eggs in them. But in a big cotton ball, the seeds are hidden away between these tough fibres. The beetles must dig their way in and try to find the actual seeds. Some beetles do succeed and lay their eggs in the seeds, which then host little weevil grubs, which feast on the seed's food stores and kill the little plant embryos. But many seeds remain unparasitized. If they land in favourable places and survive until the onset of the spring and summer rains, they rapidly germinate and become new little climbers.
Growing the Climbing Cotton
People all over the world are starting to realize what potential for loveliness this species has. And this, while here in South Africa it still receives so little recognition! The climbing cotton has numerous points of attraction. Those big flowers, in particular. In the garden, its height can be controlled so that the flowers are more easily visible. And you can go out and have a look at your plants during the night. But as I've said, some flowers do remain open for a bit of the daytime.
Aside from the flowers, this plant's leaves are large and luxuriant and it's a good foliage specimen. The fluffballs that follow the flowers also have their charm. And lastly, the big, tuberous base of the plant, called a caudex, can become an attractive, fat, basal trunk. A plant can be lifted a bit out of the soil to display more of this thick tuberous base. Plants that are like this are called caudiciforms, and there's a worldwide community of plant growers who are specifically interested in them. The climbing cotton can develop a basal caudex at least 15 cm/6" in thickness. I've seen wild plants that, if dug up, I'm sure would have had tubers far thicker than that. Locally, some people eat the tubers during times of famine, but I reckon they're not very appetizing. They're also used medicinally, supposedly to purify the blood.
The species is easy to grow from seed. Seeds are easily found in the veld over here where I live, and I go and gather fluffballs at the end of winter. My own garden plants also set seed and I pick the fluffballs up from the ground as soon as they fall, so as to give the beetles not enough time to find them. The seed must be extracted from the fluff, to improve its chances of germination. I plant my seeds directly in the growing medium but some people find it better to germinate the seeds in moist, clean cotton pads (real cotton!) and plant them out into soil once they have germinated strongly.
The young plants grow rapidly. I find that in their first year they don't lengthen much, but make some nice large leaves and start to form their thick tubers. In their second or third year they start sending up trailing stems, and start flowering after three to five years.
These plants will grow outdoors only in warm regions receiving little frost. They can grow in full sun or shade. Planted beneath a large tree, they'll rapidly send tendrils up into it. These can reach a height of 10m/33' or more. The plant can also be planted next to a fence or trellis, and will send tendrils that will scramble all over it. It enjoys regular but not excessive water in summer, and dry conditions in winter. Most or all of the leaves will fall in the autumn and early winter. In colder, wetter climates, the plants can be grown indoors. I would recommend large clay pots for them. Also put in a wooden post or lattice frame for the stems to climb over. If this is done in a decorative way, your plant can be very aesthetic-looking even while growing fairly wild and unrestrained. Still, it would eventually be necessary to prune back some of the wilder trailing stems to keep the specimen neat. It can also be shaped into an interesting specimen with lots of character. It doesn't mind trimming, often responding with fresh new, vigorous growth after a severe pruning. In a clay pot indoors, do not let the plant dry out completely over the winter, but give it just a little bit of water every two weeks or so. Sometimes tubers that go dormant in winter have difficulty getting out of dormancy in the summer and you may be stuck with a tuber that is still alive but won't form new stems and leaves. Some people have found that completely repotting these stubborn tubers shocks them out of their dormancy. But in my experience, most of the plants don't do this, but grow dependably and vigorously.