Sclerocarya birrea subsp. caffra
Marula
These two Marulas near Malalane show the relatively high-branching, robust trunk and the rounded, spreading crown typical of this species. Once this growth form is recognised, Marulas can be identified fairly accurately from some distance away.
Trees may reach about 18 metres in height, with particularly wide-spreading crowns.
Marulas are deciduous, standing leafless during the long, dry winters.
Without foliage, the thicker branchlets and their blunt tips are more evident, and this feature is an early key to to identity. The False Marula, or Lannea schweinfurthii, is a similar tree in many respects, but its thin branchlets are a feature distinguishing it from Marulas.
Bark is one of the key identification features of the Marula.
Bark is grey to brown with a characteristic mottled appearance. Oval pieces of bark lift off, leaving depressions of lighter-coloured under-bark.
Elephant tusks damage and lift off sections of bark, but the tree gradually heals and survives the injuries.
Compound, imparipinnate leaves . . . two petiolule designs!
The leaf on the right is Marula, or Sclerocarya birrea, and the leaf of the left is the False marula, or Lannea schweinfurthii. These two species of tree from the Mango family are often confused with one another.
The important feature separating these two leaves are the petiolules, or the absence thereof. The Marula's petiolules are long and slender. Petiolules are absent or minimal for the False Marula, with the terminal leaflet supported on a long petiolule. This distinction is a quick way to decide, 'Marula or False Marula?'
Marula leaves have 3 to 7 pairs of opposite or sub-opposite leaflets, and a terminal leaflet. Leaflets are green above and much paler below. The leaflet apex tapers broadly with a narrowly attenuate tip.
Leaflet margins of mature leaves are entire, but young leaves are distinctly toothed.
Note how the leaves and fruit are crowded at the end of the branch, supported and fed by thicker branchlets and blunt tips. Leaves are alternate or spiralled.
Some Marulas never bear fruit!
Marulas are dioecious.
Male and female unisexual flowers occur on separate trees. Male trees never bear fruit.
Separating male from female flowers can be misleading because female flowers contain conspicuous staminoids, or sterile stamens, giving the suggestion of a male flower. But growth forms identify flowers of each sex.
Female flowers are solitary or in small groups, each having a stalk or pedicel. The ovary is almost spherical, and is superior. Stigmas are peltate, or shield-shaped, and styles are short.
Male flowers occur along racemes, with flowers opening successively toward the apex. Racemes may be up to 8cm in length.
The image above shows male flowers along a short raceme. Note the wine-red colour of the budding flowers
Flowers emerge in spring, either before or together with the leaves, and the flowers are pollinated by insects.
Fruits are plum-sized drupes, oval or spherical in shape.
The exocarp is thick and leathery, and covers a fairly shallow, fleshy, white mesocarp. The stone, or endocarp, within is hard and encloses one or two seeds.
Green on the tree, the fruits falls to the ground, where they ripen to a light yellow colour. The fruits in the image below are ready to fall to the ground.
Fruits ripening on the ground emit a signalling scent!
Humans, elephants, birds, baboons, rhinos, civets, warthogs and many others are drawn to the tasty food that is waiting. The flesh is rich in vitamin C, and is tasty, with a slightly tart citrus flavour. The tree's tactic is to provide abundant, attractive food with its seeds encased in a tough, protective, inner package to survive passage through highly acidic digestive systems. Thus, the tree's seeds are distributed far and wide.
Elephants have a strong liking for Marula fruits, and they are great transporters of the kernels. Their digestive systems scarify the inner stone before it is discarded in dung, ready to germinate some distance away from the mother tree.
Kernels found in archaeological sites show that Marulas have travelled with human populations in their migrations across Africa over millenia. Nutritious fruits or their inner nuts will be carried by people on the move, helping the species to widen its distribution.
The story of the inner stone, or kernel, is shown in the next image.
Hard nut? The genus name is well chosen!
Sclerocarya comes from the ancient Greek words 'skleros' meaning hard and 'karyon' meaning nut.
Three fruits on the left, above, are as you may see them ripening on the ground. Moving to the right are two fruits with portions of the exocarp removed to show the inner mesocarp, with its pale, tasty flesh.
Further to the right are four 'stones' or endocarps. The flesh of the fruits has been eaten and the stones abandoned to dry out on the ground. How do the seeds locked inside this super-hard casing germinate?
Little round 'plugs' or caps, or lids, are evident on the surfaces of the stones. Remarkably, these plugs will fall away, exposing the seeds and enabling them to access conditions for germination.
Down the right hand side of the image are stones cut in half (with a hacksaw!) revealing the inner seeds. Those seeds may grow into the next generation of mighty Marula trees!
A breath-taking new day begins near Punda Maria. This magnificent Marula glows in the early morning sunlight, dwarfing Michele Hofmeyr at its base.
Marulas are among the greatest trees of Africa, and are highly valued by indigenous peoples!
As a nutritious food source, Marula fruits are among the finest. The fruit pulp is four times richer in vitamin C than orange juice, and can be made into delicious jelly or a potent alcoholic drink. The seeds contain a protein-rich oil, and are often eaten raw or added to stews or porridge.
Marulas tolerate many soil types, and are found across Kruger Park, except for one or two micro regions.
