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Sweet Thorn
Vachellia karroo
SA tree no: 172
English: Sweet Thorn, Cape Gum, Cape Mimosa, Cape Thorn Tree, Cape Thorn-tree, Gum-arabic Tree, Karoo Mimosa, Whitethorn, White-thorn
Afrikaans: Soetdoring, Kaapse Doringboom, Fyndoring, Karoodoring, Karoo-doring, Karoodoringboom, Khoeboom, Khoedoring, Mimosadoring, Mimosadoringboom, Witdoring, Witdoringboom
Xhosa: Umnga, Umnga-mpunzi
Zulu: umuNga, Umunga
N. Sotho: mookana
Tswana: mooka
Misapplied or old scientific names: Acacia karroo, Acacia capensis, Acacia dekindtiana, Acacia hirtella, Acacia horrida, Acacia reticulata, Acacia robusta, Mimosa capensis, Mimosa eburnea, Mimosa leucacantha, Mimosa reticulata
Vachellia karroo (formerly Acacia karroo), commonly known as Sweet Thorn or Soetdoring, is one of South Africa's most recognisable and useful trees. It has a rounded crown and branches fairly low down on the trunk, varying in shape and size, reaching up to 12m where there is ample water.
The bark is red on young branches, darkening and becoming rough with age, sometimes showing an attractive reddish hue in deep fissures. Its bright yellow, ball-shaped flowers appear in early summer, attracting numerous insects, and are followed by flat, crescent-shaped seed pods.
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Distinguishing features:
Rounded crown.
Red bark on young branches, becoming dark and rough with age.
Finely textured, dark green leaves.
Bright yellow, ball-shaped flowers.
Flat, crescent-shaped seed pods, sometimes constricted between seeds.
Overall Appearance:
Vachellia karroo is a medium-sized, thorny, deciduous tree native to South Africa. It is easily recognisable by its long, straight, white thorns. It has a rounded crown and a characteristic reddish-brown bark.
Height:
The tree typically grows to a height of 5-12 meters.
Width:
The crown spread can reach 8-15 meters.
Leaves:
The leaves are bipinnate, meaning they are divided into numerous small leaflets.
These leaflets are small, oblong-shaped, and finely textured.
They are a light green color.
Flowers:
The flowers are small, globular heads of numerous yellow stamens.
They are fragrant and appear in abundance during spring.
Flowering Season:
The main flowering season is typically from August to October.
Fruits:
The fruits are flat, brown pods that contain numerous seeds.
These pods mature from late autumn to winter.
Seeds:
The seeds are small, oval-shaped, and hard.
They are typically dark brown or black in color.
Bark:
The bark is the most distinctive feature of the tree. It is a reddish-brown color, often with deep fissures and ridges. This reddish-brown bark is the origin of its common name "Rooikrans".
Wood:
The wood is hard, dense, and durable. It is reddish-brown in color and has a fine grain.
Soil Type:
Vachellia karroo is adaptable to a variety of soil types, including sandy, clay, and rocky soils.
Aspect:
Vachellia karroo is a sun-loving tree and thrives in full sun.
Edibility:
The pods and seeds are edible and have been used as a food source by some indigenous communities.
Uses:
Gum: Edible, sweet-tasting gum is exuded from wounds in the bark, eaten by people and animals. It was also commercially valuable as "Cape Gum" for making confectionery.
Fodder: Leaves, flowers, and pods are eaten by stock and game.
Rope: A strong rope can be made from the inner bark.
Bee-farming: The flowers produce nectar and pollen for bee-farming, yielding pleasant-tasting honey.
Medicinal: Used for wound poultices, eye treatments, and cold remedies. Also used to treat cattle with tulp poisoning.
Shade and windbreak: Suitable for planting on small holdings and farms.
Ecology:
Pioneer species: Able to establish itself without shade, shelter, or protection from grass fires.
Long taproot: Enables it to use water and nutrients from deep underground.
Nitrogen-fixing: Improves soil fertility, benefiting nearby plants.
Food source: Provides food for various animals, including insects, stock, and game.
Distribution and habitat:
Found from the Western Cape through to Zambia and Angola.
Occurs in a variety of habitats, from low-lying areas to highveld.
An indicator of sweet veld, prized for good grazing and fertile soils.
Derivation of name:
Vachellia is derived from the name of George Harvey Vachell, a chaplain and plant collector who worked for the British East India Company in Macau and collected plants in China.
The genus Vachellia was previously part of the genus Acacia, but was separated in 2005
The old name Acacia is derived from Greek "akis" a point or barb.
Karroo is one of the old spellings of karoo which cannot be corrected because of the laws governing botanical nomenclature.
The sweet thorn gets its common name from the edible gum it produces.
Historical aspects:
The thorns were used by early naturalists to pin insects. The tree is integrally part of South Africa's history, used for everything from raft-making to sewing needles and fencing.
Interesting facts:
The sweet thorn gets its name from the edible gum that oozes from its bark, which both people and animals enjoy!
This tree is a survivor! It can grow without any shade or shelter and can even regrow after a fire.
Its roots dig deep, helping it find water and making the soil better for other plants to grow nearby.
The town of De Doorns ("the thorns") is named after this tree because it's so common in that area.
Growing tips:
Planting location: Makes a beautiful garden specimen. Avoid planting near paving or buildings due to invasive roots.
Soil: Very adaptable to soil types.
Hardiness: Frost and drought hardy.
This plant is a fantastic alternative for:
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