Plantbase

Botanical name:

Portulacaria afra

Common names:

Porkbush, Elephants Food (E)
Spekboom (A)
iNtelezi, isiDondwane,isAmbilane, iNdibili, isiCococo (Z)
iGqwanitsha (X)

Plant family:

Portulacaceae

Plant categories:

Trees; Shrubs; Cacti and Succulents; Non-herbaceous Perennials

Name derivation & history:

The name Portulacaria is composed of Portulaca + aria suggesting a similarity to the genus Portulaca.

The word afra is in reference to the fact that the plant occurs in Africa.

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.

Leaf habit:

Evergreen

Height:

Usually 1½ to 2 metres, but up to 5 metres

Width:

Usually 1 to 1½ metres

Plant shape:

Irregular shaped plant that is normally quite dense.

Leaf description:

Small round succulent leaves

Flower description:

Small, star-shaped pink flowers appear from late winter to spring.

Flower colour:

Pink

Flowering months:

Late winter to spring.

Bark or stem description:

Red stems

Natural distribution:

Eastern parts of South Africa from the Eastern Cape northwards into KwaZulu-Natal, Swaziland, Mpumalanga and the Limpopo Province as well as Mozambique.

Habitat:

It is found in warm situations on rocky slopes in succulent karoo scrub, thicket, bushveld and dry river valleys.

Water requirements:

Waterwise (little water required)

Frost tolerance:

Semi-hardy only when mature

Light conditions:

Sun; semi-shade

Interaction with physical surroundings:

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 pork bush survives and spreads successfully whereas outside the park the plant is becoming sparse as a result of overgrazing and poor regeneration. A very interesting mistletoe, Viscum crassulae, parasitizes this plant. The foliage of this mistletoe is hard and rough in contrast to the soft and smooth leaves of the porkbush. The small red fruits of the mistletoe are enjoyed by birds who eat the sweet outer layer and discard the sticky seed which is normally wiped onto a branch by the bird. There it germinates directly through the bark of the porkbush with specialized roots called haustoria which extract moisture and soil nutrients from the host, while the green leaves allow the semi-parasitic mistletoe to produce its own food.

Highly favoured by tortoises.

Uses & Cultural aspects:

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.

It is also recorded that a small sprig of porkbush steamed with a tomato bredie (stew) imparts a delicious flavour.

The honey made from the flowers of porkbush is said to be " unsurpassable in flavour and texture" by one reference (Roberts 1990).

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 earth's atmosphere; it is produced in excess by burning of fossil fuels.

Cultivation:

The porkbush is easily propagated from cuttings, the seed is not often available. Cuttings or truncheons strike root easily and can even be planted directly into the ground where they are to be grown. Alternatively cuttings can be taken in the normal manner and allowed to dry out for a day or two in a cool, dry place and then planted in washed river sand. Keep them in a warm shady position until they are rooted and ready to be planted out. Cuttings root quickly and can usually be planted out after four to six weeks.

This versatile plant can be used in full sun or semi-shade in dry areas or even in well-watered flowerbeds. It can tolerate a moderate degree of frost, especially when mature. (It is also used as a rootstock for grafting the closely related but more difficult to grow Ceraria namaquensis (Namaqua porkbush) which cannot tolerate water around its roots as it comes from very dry areas).

The porkbush can be used as a screen or even a clipped hedge. It also makes a handsome and hardy Bonsai. Various different forms are found in cultivation, most of which originate from the Karoo Desert. These forms include a prostrate low growing ground cover, 'Prostrata'; a shrubby form with small round leaves which turn an attractive yellow in full sun, 'Aurea' and 'Foliis variegatus' a slow growing variegated form which is well suited to pot culture. Another variegated form known as 'Medio-picta' has green leaves with whitish markings spreading from the centre. A large-leaved form known as ' Limpopo ' has much larger, more ovate leaves that can measure up to 20 to 30mm long and 15 to 20mm wide. This form represents the northern populations which extend into the northern provinces of South Africa and Mozambique.

Notes:

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 Pork bush consequently has the ability to remove more carbon from the atmosphere than an equal amount of deciduous forest.

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.

References:

South African National Biodiversity Institute, South Africa.

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