Porkbush/Spekboom /Portulacaria afra.
Family: Portulacaceae
Common names: Porkbush, Elephant Food, Purslane (English);
Spekboom. Olifantskos (Afrikaans);
iNtelezi, isiDondwane, isAmbilane, iNdibili, isiCococo (isiZulu);
iGqwanitsha (isiXhosa)
Description
Portulacaria afra is a small-leaved succulent plant found in South Africa 1 . The
Spekboom is an attractive, evergreen succulent shrub or small tree that can reach 2 - 5 m in
height, although usually around 1.5 - 2 m in a garden situation. It has small round succulent
leaves and red stems. Small star-shaped pink flowers are borne en masse from late winter to
spring although flowering in cultivation is often erratic. They are a rich source of nectar for many
insects, which in-turn attracts insectivorous birds. The plant is resilient even when exposed
to weather extremes and is exceptionally easy to grow 2 .
Uses
According to a study conducted on fresh and processed leaves of Portulacaria afra,
it was found that the plant can be harnessed as a sustainable, nutritious food source
and ingredient 3 . The study also determined that the plant has undervalued medicinal
properties. The indigenous edible spekboom can be used as a natural remedy for
various ailments such as diabetes, high blood pressure, and fever 3 .
The leaves of the Porkbush can be eaten and have a sour or tart flavour. It is heavily browsed by
game and domestic stock and highly favoured by tortoises. The Porkbush has also been
indicated as a soil binder for preventing soil erosion. Traditional uses also include the increasing
of breast milk by lactating mothers. The leaves are used to quench thirst, sucking a leaf is used
to treat exhaustion, dehydration and heat stroke. Crushed leaves can be rubbed on blisters and
corns on the feet to provide relief. The leaves are chewed as a treatment for sore throat and
mouth infections while the astringent juice is used for soothing ailments of the skin such as
pimples, rashes and insect stings. The juice is also used as an antiseptic and as a treatment for sunburn.
The Porkbush and Climate Change
Recent research has shown the Porkbush to be an excellent carbon sponge as it has the ability to sequestrate (absorb) free carbon from the atmosphere which is used to make plant tissue.
Carbon is one of the major greenhouse gases which are responsible for the warming of the
earths atmosphere. It is produced in excess by burning of fossil fuels. Currently, humans are
producing atmospheric carbon faster than the environment can absorb it, causing a deficit which remains in the atmosphere and causes heat from the sun to be trapped instead of being radiated back out into space. The porkbush has the unique ability to absorb more carbon from the atmosphere than most other plants and it does so particularly efficiently. A stand of Porkbush in an arid or semi-arid region has the ability to remove as much carbon from the atmosphere as an equal amount of deciduous forest. The plant has the potential to sequester large amounts of ecosystem carbon. According to research from 2014, spekboom can capture and store between 2.9 and 8.6 tonnes of carbon dioxide per hectare per year in its above ground biomass.
How does it manage this? The Porkbush has the ability to make use of two different
photosynthetic pathways, when conditions are favourable it manufactures its food to sustain
growth by using the same method (pathway) that most other plants use. However, when
conditions are not favourable and other plants have to shutdown and wait for sufficient rain, the porkbush can switch to a different pathway called CAM (Crassulacean Acid Metabolism)
whereby it can continue to grow and slurp up huge amounts of carbon despite adverse climatic conditions. This allows the plant to excel in the arid or semi-arid conditions that it is native to. Further to its carbon habit, the large spreading shrub covers and shades the soil from the harmful rays of the sun creating a favourable environment under the bush for insects and other wildlife to inhabit, while the dead organic matter which accumulates under the bushes has an enriching effect on the soil. This further enrichment of the soil improves its water-holding capacity which further benefits the porkbush as well as other plants and animals including micro-organisms, which occur in the area.
Projects now active in the areas where the Porkbush occurs seek to utilize it as a rehabilitation aid to restore over-utilized natural habitats to their formerly productive state. At the same time these sites act as carbon sinks (kind of carbon bank) where carbon can be collected and used where it belongs and is productive to both humans and the environment. Potential earnings through carbon credits could be translated into social upliftment in the areas where this plant is being utilized.
It has now been shown to be effective in carbon sequestration (binding atmospheric carbon
which is responsible for climate change).
The Porkbush belongs to a large and widespread family (Portulacaceae) which includes the
popular Portulaca and is often sold in garden centres and grown in domestic gardens as an
annual for summer colour, although this is not a South African species. Other members of this genus include Portulacaria armiana and Portulacaria pygmaea the former has larger grey green leaves and is native to Namibia although it is not often cultivated, whereas the latter is a dwarf succulent shrublet with small, thickly fleshy, grey green leaves and occurs on rocky hillsides in Namaqualand, South Africa.
Ecology
Interesting ecology has been observed with this plant in the Eastern Cape where it forms part of the diet of the Addo elephants in the Addo National Park. Elephants eat the plant from the top downwards allowing the plant to spread itself vegetatively by spreading horizontal branches at ground level. Outside the park the plants are eaten by goats who eat the plant from ground level upwards preventing the plant from spreading vegetatively. Consequently these plants must rely
solely on seed to proliferate the species which often proves difficult in such a dry climate. As a result it was observed that inside the park where the plant is subjected to browsing by elephants the Porkbush survives and spreads successfully whereas outside the park the plant is becoming sparse as a result of overgrazing and poor regeneration.
The leaves are used medicinally and in traditional home construction. Here are the most popular traditional and contemporary uses of spekboom leaves:
Sucking a leaf to quench thirst, treat exhaustion, dehydration and heatstroke.
Using crushed leaves to provide relief for blisters.
Chewing leaves can treat a sore throat and mouth infections.
Juiced leaves are used as an antiseptic and to soothe skin ailments such as pimples, rashes, insect stings and sunburn.
In certain areas, the stems are used to help build huts/homes. The stems are dried and used as thatch for rooves of the huts/homes.
In Mozambique, breastfeeding mothers eat spekboom leaves to increase their milk supply.
During famine, the Zulus eat the leaves raw.
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