Mountain Cabbage Tree
Willem says: 'The Phyto-Philes are for plant lovers of every size and shape, colour and flavour. As with my Colours of Wildlife column, I'll be featuring one species per article, illustrated with sketches, paintings, and/or photos. Over time I hope to be showcasing the amazing diversity of weird and wonderful plants that occur in South Africa, while also from time to time looking at the flora of other countries. While featuring many spectacular species, I'll not be neglecting the smaller, more humble kinds that are nevertheless fascinating in their own right.'
Time for another weird tree! The Mountain Cabbage Tree, Cussonia paniculata, is well known in South Africa, with a wide distribution covering various different kinds of environment. It is also frequently planted in gardens. It most frequently grows at high altitudes in grasslands, sometimes in open grassland as in my photo, sometimes on hills, sometimes in thickets with other trees and shrubs. It also grows on forest edges and, in the south of its distribution, in semi-arid scrub vegetation.
Cabbage or Tree?
Cabbage trees are not at all closely related to cabbages. They constitute the genus Cussonia, of which several species are found in South Africa. The genus name comes from Pierre Cusson, a French botanist of the eighteenth century. The mountain cabbage tree is the one most widely distributed over here. It is a small tree, rarely exceeding 3 m/10' in height. It is usually single-stemmed and may be entirely unbranched. Old trees form canopies of several branches fairly short but thick and stubby branches, as you can see in my photo. At the tip of the trunk, or of each branch, there is a cluster of leaves. This tree has very distinctive leaves. They are very large, reaching 60 cm/2' in diameter, with petioles (leaf stems) up to the same length. The leaf is divided into leaflets arranged in a radiating formation. There can be up to 9 leaflets per leaf. They usually have wavy or lobed margins and are greyish or bluish green in colour. This colour is visible from a great distance and along with the shape of the trees make them very easy to identify. Close-up they can be seen to have thick, corky bark, which protects them against grass fires, which can be frequent in their habitat. This tree with its squat appearance, thick bark and tuberous roots can be considered a semi-succulent.
There are two forms of this tree. The subspecies paniculata occurs in the south, in the Karoo region of the Western and Eastern Cape provinces. This one has leaves with fairly straight margins. The subspecies sinuata occurs farther to the north, and is the one with the wavy, lobed, incised leaf margins. This is the one in my photo and illustration, as it is the one that is more widespread, occurring over the rest of South Africa, and also the one I most frequently encounter.
Flowers in Panicles
This tree's species name refers to its panicles, or branched flower stalks. These stalks are very big and emerge from the tips of the stems. They are sometimes erect, sometimes hanging down. Each branch of the panicle carries a spike on which the flowers are densely packed. The flower buds are round and the yellowish-green flowers open one by one as you can see in my drawing of the inflorescence. The flowers, once pollinated, turn into similarly round fruit that turn purple when they're ripe. They're eaten by a variety of fruit-eating birds.
Humans can get food from this tree, too! The thick, tuberous roots can be peeled and then eaten. Perhaps this is where the name 'cabbage tree' comes from, but they must not taste very good, since they're considered an emergency food. They also contain lots of water and so in semi-desert regions are sought out as a moisture supplement.
A Craggy Character
This is a tree with character, and it also lends character to the landscapes in which it grows. I always love seeing it in the wild. The photo you see here was taken in the Suikerbosrand Nature Reserve near Heidelberg. The reserve preserves a wonderful example of the grassland that once covered what is now the province of Gauteng. The rolling hills are covered with tall, waving grasses, with only a few trees among them. This tree, along with mountain aloes, Ouhout ("old wood") and the sugarbush or Protea trees for which the reserve is named, form the main woody species that punctuate the grasslands on the slopes, on rocky outcrops or on the banks of streams. The reserve is beautiful and scenic, and gives one an idea of how this entire region must have looked before the arrival of Europeans and the massive development, industrialization and urbanization they brought.
I've also seen many of these trees in the Drakensberg range of Kwazulu-Natal. These are the highest mountains in South Africa and again wonderfully scenic, and they, fortunately, are still mainly pristine. Mountain cabbage trees are some of the most cold-resistant of our trees, and grow above the forest line in these mountains, at an altitude of over 2000 m/6600'. There they grow in open grassland along with other high-altitude trees like Notsung, Shell-flowers, Proteas, Buddleias and Bottlebrushes. Growing one-by-one in the open grassland, against the dark green background of forest patches, or next to huge, black rocks, they always stand out strikingly. They also vary among themselves, no two trees being quite alike in shape.
Growing Mountain Cabbage Trees
This species can easily be grown from fresh seed sown in a well-draining seedling soil. Over here in South Africa they are available from many nurseries as well. The trees are fairly frost-resistant, although not as much as you might think from their high-altitude habitat. In high mountains they often grow in spots receiving a lot of sunlight or in the shelter of rocks or other trees, which gives them ample frost protection. So in gardens receiving moderate frosts they should also be planted amidst sheltering plants or in a warm, sunny corner. They are drought resistant, enduring a typical South African dry season of six or more months without rain. They are evergreen once established. They don't take up much space, rarely exceeding 8 m/27' in height and 3 m/10' in spread. They will attract birds, not just for their fruit, but also because their soft wood can easily be excavated by woodpeckers and barbets. Other hole-nesting birds may take over these cavities later.
Outside South Africa these trees could probably survive in southern Europe and the southwestern USA, and the warmer parts of Asia. In colder climates they can be grown in hothouses or as container plants on a sunny porch or indoors if there's enough room.
Cultivated plants are sometimes afflicted by something that deforms their leaves. Round 'bubbles' of tissue form on the leaf surfaces. These are galls caused by the larvae of wasps. It doesn't really harm the tree, but can be a bit unsightly. However, as trees grow bigger they often 'outgrow' this problem.