The fragrant sweet thorn is one of the
hardiest trees in southern Africa and is therefore recommended to plant
throughout farmlands and gardens. It is a highly adaptable
species, equally at home in humid forest, on savanna, or in semi-desert. Once
established, the sweet thorn can handle almost any adversity, even wildfires. A
medium-sized tree with a rounded canopy is breath taking when in full flower.
Fast growing and extremely adaptable, used as shade trees, windbreaks or
barriers on farms, in gardens and public areas.
WALL OF THORNS
Sweet
thorns are leafless during the winter, when the density of their long white
thorns is clearly visible. This makes it a favourite nesting tree for birds, as
they deter all but the most persistent nest predators. The tree’s daunting
“thorns” are technically spines, developed from leafy outgrowths (stipules) at
the base of the leaf-stalks and are up to 5cm long. Being dressed in spines is
enough to put off many, but not all grazing animals. Giraffes, in particular,
have no problem wrapping their leathery tongues around its branches to feed on
the fine, mimosa-like leaves. The bark, flowers and nutritious seed pods also
provide sustenance to animals, as does the gum that oozes from wounds in the
bark, a special favourite of vervet monkeys and lesser bush babies.
FODDER AND BY PRODUCTS
Plant
this tree on farms as a windbreak around buildings, livestock pens, and croplands.
Exceptionally useful, adaptable and versatile, the Sweet Thorn is fast-growing
and makes a good shade tree for the garden. It is an outstanding fodder tree.
The leaves, flowers and pods are browsed by game and stock. Young leaves are
enjoyed by game, and the Sweet Thorn is a favoured food of the Black Rhino. The
flowers attract monkeys, birds such as sunbirds and parrots, and insect
pollinators. The pollen produces good honey. The tree provides food for the
larvae of several butterfly species (e.g. Club-tailed Charaxes). The clear
golden to red gum has a pleasant, slightly sour tasted and is eaten by people,
monkeys and bush babies. The gum is used in pharmaceutical products, for
confectionery and as an adhesive. The bark (containing 19% tannin) is used for
tanning leather red. When wet, the pliable inner bark can be used to make an
extremely strong rope. Roasted and ground seed can be used as a coffee – but it
is an acquired taste! The wood is used for fencing posts and to build kraals to
protect cattle. The bark, gum and leaves have been used as a soothing agent and
astringent for colds, conjunctivitis and haemorrhage.
CULTIVATION
Easily
propagated from seed covered with boiling water and soaked overnight before
sowing. Fast growing and tolerant of many soil types, the sweet thorn is able
to establish itself without shade or shelter, and is even impervious to fire.
Seedlings that have survived their first year can be burnt to a crisp only to
sprout new stems, thanks to the energy stored in their roots.
FLOWERING AND TREE SIZE
In
early summer, the sweet thorn’s canopy erupts with hundreds of yellow pompom
shaped blooms. The tree’s long flowering season from October to April offers a
reliable source of pollen and nectar to bees, making this an important species
for honey production. Each pompom inflorescence is made up of many individual
flowers. By no means a large tree, approximately 8m x 8m. Bigger specimens
reach around 12m (40ft) in height. The sweet thorn is also relatively
short-lived, with a maximum lifespan of 30 to 40 years. It is however, able to
cope with extreme conditions. As well as being frost-resistant, the sweet thorn
can survive drought thanks to its long taproot, which enables it to draw on
water reserves deep underground. When nutrients are scarce, it can generate its
own supply of nutrients by using structures on its roots that house
nitrogen-fixing bacteria. Within root nodules, bacteria produce an enzyme
called nitrogenase. This converts gaseous nitrogen into soluble ammonia, a form
in which the nitrogen can be used by the tree. In return the bacteria are
provided with food in the form of sugars.
REFERENCED
PUBLICATIONS: FLORA INSIDE THE SECRET WORLD OF PLANTS, KEW ROYAL BOTANIC
GARDENS; INDIGENOUS PLANTS, A SOUTH AFRICAN GUIDE AUTHORS PITTA JOFFE &
TINUS OBERHOLZER; INDIGENOUS PLANT PALETTES AUTHOR MARIJKE HONIG
