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gardening with indigenous traditionally-useful plants
Rholidldla Nelson Mandela’s Pepper-bark Tree 14 years after he planted it in Kirstenbosch. Photo: P. Xaba.
The Pepper-bark Tree
by Phakamani Xaba, SANBI, Kirstenbosch National Botanical Garden and Rosie McVay
This is the eleventh in a series of articles on indigenous plants that have traditionally been
used by humans in southern Africa for food, medicine, crafts, and charms. Some of these
plants are now threatened while others that once formed an important part of our diet
have been forgotten. It is hoped that these articles will help revive an interest in growing,
using and conserving a valuable indigenous resource. Please note that cited traditional
information about medicinal use of plants does not constitute a recommendation for
their use for self-treatment. Improper or uninformed use of wild plants can be extremely
dangerous.
Learning to grow and use these plants will help:
· Promote sustainable use of these plants.
· Provide practical growing information especially for threatened species.
· Reduce pressure of harvesting from natural populations in the wild.
· Inform the general public about indigenous useful plants.
· Preserve indigenous knowledge.
T
he Pepper-bark Tree of southeastern Africa, Warburgia salutarus,
is endangered in the wild because of
heavy harvesting of its much sought-after
bark for traditional medicine. In central and
eastern Africa closely related species, known
as ‘Karambaki’, have been used medicinally by
Arab and local residents since ancient times.
Scientifically, the sharply peppery-tasting bark
and leaves contain a variety of compounds
that have useful antibacterial, anti-fungicidal
(particularly against Candida yeast infections),
anti-ulcer and diuretic properties.
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VELD&FLORA | MARCH 2010
Fortunately it is relatively easy to grow from
cuttings so small commercial plantings of the
tree in Mpumalanga ensure a steady future
supply for the traditional medicine market,
hopefully reducing pressure on remaining
natural populations of the Pepper-bark.
Where do we find Pepper- bark Trees?
The Pepper-bark is a medium-sized tree
growing in evergreen forest or woodland
on hill and mountain slopes and in wooded
ravines in north-eastern KwaZulu-Natal and
eastern and northern Limpopo (Soutpansberg
mountains) and Mpumalanga in South Africa.
It is also found in Swaziland, Mozambique,
Zimbabwe and Malawi. Its closest relatives
in the genus are central and east African.
It is rare in the wild, probably because of
overharvesting of this much-prized source
of traditional medicine, and is listed as a Red
Data Book threatened species.
What does it look like?
Pepper-bark is a medium sized tree (4-8 m) in
height, rarely larger, with a delicately rough,
mottled, shiny brown bark that is reddish on
the inner side. Leaves are simple, without
stipules, alternate, almost whorled, 10 cm or
more in length, elongate obovate, a glossy
deep green in colour with a yellow-green
mid-rib. The bark and leaves taste sharply
peppery.
Small greenish-yellow flowers appear
between the leaves during April and May
followed by the round to pear-shaped, berrylike green fruit, up to 4 cm in diameter, which
turn purple with a dusty bloom when ripe
during Spring to December. Leaves, inner bark
and fruit all have a sharp strong peppery taste
which becomes apparent after a few seconds.
The fruits contain several flat seeds that are
recalcitrant (the seeds die when dried out).
Fruit flies and monkeys are so drawn to the
fruits that harvesting the seed is extremely
difficult. Most natural propagation in the wild
appears to be vegetative.
Conservation status and threats
Warburgia salutaris is listed as Endangered in
the latest (2009) IUCN Red List of Threatened
Species. Apart from some remote populations
in Limpopo Province, the tree is extremely
hard to find in the wild and is on the border of
becoming extinct through much of its natural
range. Overharvesting, indigenous timber
clearing for commercial forestry, agriculture
and human living requirements and the poor
germination of seed all threaten the tree’s
future existence in the wild.
Considerable effort is being put in to
bringing the species back from extinction. In
1996 the Pepper-bark was named as Tree of the
Year as part of the South African government
forestry initiative to promote indigenous tree
conservation and knowledge. A highlight
of the campaign that year was when former
State President Nelson Rolihlahla Mandela
planted a Pepper-bark at the entrance to
Kirstenbosch.
Fortunately the Pepper-bark grows easily
and well from cuttings and a number of
experimental plantings have been done by
botanical gardens and conservationists as
well as by some commercial growers. These,
however, can only be harvested when the
trees are at least 10 years old.
A particularly impressive conservation effort
An easy guide to growing
ACTIVITY
PEPPER-BARK
ENVIRONMENT REQUIRED
FOR SUCCESS
TREATMENT
TIME
REMARKS
Seed
harvesting
and
preparation
4 cm in diameter, oval fruits
are dark purple when ripe.
Soak fruits in cold water
overnight and then remove
the skin and flesh to expose
seed.
Seed ripens between October and December.
Seed
sowing,
germination
Sow seed in tray with riversand and lightly cover them
by sieving river-sand on top.
Keep tray moist. Treat the
seed with an anti-fungicide if
growing in large volumes.
Leave seedlings in trays until they reach
Seeds will germinate and emerge in about 21 days;
about 80% will germinate within 2 months of sowing. 5 cm in height (2 leaf stage). Pot the
seedlings into a small container with a
general mixture of sand (1), loam (2) and
compost (1). Add Bounceback® to your
potting mix.
Vegetative
cutting
preparation
Cut 15 cm apical shoot tip
cuttings in early morning
and keep them in a bucket
of water until ready to stick
in a sandy medium such
as coarse river-sand or
silica-sand. Semi-hardwood
cuttings root best. A
hardwood rooting hormone
helps speed the process.
Trim cuttings to 3-4 nodes/810 cm and strip the lower
leaves. Cut remaining 3
or 4 leaves in half. Dip the
cuttings in rooting hormone
and insert the cuttings in
a tray with washed river
sand. For optimum results,
the tray is then placed in an
intermittent misting system
with heating bench set at
27°C . Alternatively, use a cold
frame or even simpler, store
your tray with cuttings in a
shaded area.
Cuttings taken from late spring to midsummer. For
optimum rooting take cuttings in December. It takes
3-8 weeks for the cuttings to root. Weaning can be
2 weeks by which time rooted cuttings can be
transplanted into a small container. Potted plants can
be stored in semi-shade for 2-3 months then plants
can be exposed to full sun.
Rooted cuttings should be potted in a
small container with a general mixture of
sand (1), loam (2) and compost (1). Add
Bounceback ® to your potting mix. Plant
can be re-potted next summer.
Cultivation
Planting is best carried out
in the winter months (June
July). Plant in a 1m x 1m
x 1m hole with a generous
mixture of compost and a
hand full of Bounceback®
and bonemeal.
Plants thrive in full sun and do
well in light shade.
Pruning can be best done in winter. Harvesting of the
leaves can be done throughout the year with summer
being the peak season. The Pepper-bark makes an
excellent hedge when planted half a metre apart.
The Pepper-bark Tree transplants easily in
midwinter (June). Plants must be pruned
back hard, removing all leaves. The plant
should be removed with as much as
possible of the root ball. Long hanging,
excess roots can be trimmed off.
is Durban Metro’s Silverglen Nursery which
not only grows Pepper-bark cuttings on a
fairly large scale but has also been running
plant-growing education programmes and
distributing cuttings to hundreds of traditional
healers and herbalists (more than 500 by the
end of 1996) so that they can grow their own
source of supply
Presently much of the material sold on
the traditional medicine market in South
Africa is being sourced from Mozambique.
Unfortunately the steadily increasing demand
for this efficacious natural medicine for a
variety of lung, urinary tract and skin problems
outstrips supplies.
It is also an attractive, quick-growing garden
subject in frost-free areas and prefers sunny,
protected areas with well-draining soil rich in
organic material. It also makes a good hedge
subject, tolerating training and leaf clipping.
Ecology and pests
The fruit fly larval infestations of fruit
damage the developing seed, reducing its
viability. Hippo in the St Lucia Wetland area
on the other hand promote development
of Pepper-bark suckers which develop from
Seeds are recalcitrant, i.e. seed must be
planted fresh as they will not germinate
if dried out.
roots damaged by trampling. Amongst the
complex of chemicals contained in the tree
are sesquiterpenoids which appear to be
effective against army worm.
evergreen hedge. The Pepper-bark is also a
soil-improver which fixes nitrogen and its
prunings make an excellent green manure
and mulch.
Traditional and future uses
The Pepper-bark, or Isibhaha, and its close
relatives in central and east Africa have for
centuries been amongst the most soughtafter sources of traditional medicine. The
bark, roots and, latterly, even the leaves are
harvested and then dried for use in powdered
form, or as infusions and decoctions, as a
remedy for many conditions including oral
and vaginal thrush, bronchial infections,
coughs, chest complaints, colds, headache,
rheumatism, venereal diseases, toothache,
gastric ulcers and malaria. Strong and growing
demand for the Pepper-bark in traditional
medicine suggests a useful additional longterm investment strategy for farmers in areas
suitable for its growth.
Horticulturally, the Pepper-bark is a
beautiful and versatile landscape tree with
its glossy, deep green foliage and oval shape.
Pepper-bark trees planted close together
can also be pruned into an attractive
BELOW: The bark of the Pepper-bark Tree, Warburgia salutaris
with ‘lenticels’. Photo: P. Xaba.
MARCH 2010
| VELD&FLORA
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