Acacia sieberiana var. woodii (presently Vachellia sieberiana)

Description

Formerly known as Acacia siebierana var. woodii, the name has been changed to credit the original collector, George Vachell, a chaplain to the East India Trading Company, who collected and took specimens to China (1789-1839). With its classically flattened, magnificently spreading crown, deep green, feathery foliage and corky bark, it is a tree perfectly reminiscent of the African landscape.

SA Tree

Family

Fabaceae or Leguminosae (Legume or pod-bearing family).
This family is also divided into 3 subfamilies; mimosa or acacia subfamily, cassia and pea. Regarded as one of the largest, as well as economically significant families, its members have been cultivated since early times for their plethora of uses – as food, medicine, fodder, for practical use (tannins) and ornamental displays

Habitat

Grows in open grassland, bushveld, on rocky ridges, along river edges and in woodland in Natal, also in Gauteng, North West, Limpopo and Mpumalanga.
Can often be seen in the areas that transition between high and lowveld.
Loves deep, fertile soil.

Bark

A lovely creamy-yellow to greyish brown, inclined to be corky, often peeling in long, papery strips, especially on the branches.
The new branchlets tend to be densely hairy.

Foliage

Deciduous
The leaves are bipinnately compound, (70-150mm), narrowly oblong, and dark green.
The leaves and branchlets are sometimes covered in dense, fine golden hairs.
Pairs of strong, white and straight spines (up to 100mm) that are joined at the base but are occasionally absent from the tree.

Flowers

Abundance of sweetly-scented pale yellow – creamy-white puffballs, 1-4, at nodes, from September to November.

Fruit

Creamy, light brown pods. (21 x 3.5 cm)
Thick, woody textured, hairless to densely velvety and slow to open.
Usually visible during autumn, maturing from March onwards.
Smallish, ovoid, black seeds, similar to beans, are released from the pod after it has fallen to the ground.

Height

Spread

Medicinal

A decoction of the roots is used to treat stomach ache.
Infusions of the dried and powdered bark is said to help relieve inflamed urinary passages, while the pods, gum and leaves are used to treat, amongst others; colds, chest problems, eye inflammation, acne, dropsy, rheumatism, oedema, syphilis, bilharzia, and to treat infections of tapeworm.
A true medicinal wonder.

Practical

The edible gum makes a good adhesive and is sometimes even used in the ink making process.
Traditional women made a twine from the fibrous inner bark, that they then used to thread beads.
The wood is light and soft, not very attractive, and prone to attacks from borer, but was apparently used by early pioneers for wagon building. Fencing poles are sometimes made from branches.
The bark and seed pods contain tannins, used to give colour to leather.

Warnings

The leaves contain traces of hydrocyanic acid (a weak poisonous acid used in fumigation and organic synthesis) and the tree is said to release it when heavily browsed. (even present in wilted leaves).
Quantities should be limited when used as a fodder.

Wildlife

The flowers attract bees, butterflies, wasps, beetles and thrips, which in turn will lure insectivorous birds such as Bar-throated Apalis, white-bellied, Black and Collared Sunbirds.
Also, a host plant to the larvae of the common Scarlet butterfly.
The pods have a musky scent and are loved by game and livestock.
Grey hornbills crack open the pods to eat the seeds, and Wood Hoopoes scratch under the flaky bark for insects.

Advantages

A favoured nesting tree for Pied and Crested Barbets.
The flowers provide excellent forage for bees, and beehives are often placed in the tree itself.
The wide, umbrella shape crown provides wonderful shade and it makes a good bonsai subject.
Very attractive tree, especially in large gardens.
As with some other Acacia species, the roots are host to the bacteria strain Rhizobium, which converts nitrogen effectively (essential for plant nutrition), without the need for soil nitrates or nitrate fertiliser), which will benefit all the plants that grow in its vicinity.

Tolerance

It is drought resistant, fairly frost resistant (can tolerate temperatures between -2 and 40 degrees Celsius) but young tress should be sheltered against extreme frost.
As the bark is highly flammable, the tree should be protected from fire.

Growth Rate

Lighting

Soil & Water

This hardy tree will flourish even in the poorest of soils, in rocky areas, even shale.
When young, or shortly after planting, water well.

Propagation

Germinates easily from seed.
Soak overnight in hot water, plant in river sand, compost mixture.
Cover seeds with thin layer of sand, keep moist.
In colder areas, trees should be planted from seed in order for them to properly acclimatise.