One of the icons of the South African veld, Vachellia karroo, the Sweet Thorn, is a very spectacular tree when in full flower.
Vachellia karroo, the Sweet Thorn, is, in cultivation, a medium to large single stemmed, deciduous tree. With a rounded crown that is often wider than it is tall. An icon of the South African veld, Vachellia karroo is a popular choice among local gardeners as a pavement tree or as a shade tree in larger gardens. It is a very spectacular tree when in full flower.
Sub-family: MIMOSOIDEAE (Thorn tree sub-family)
- Vachellia – named in honor of Rev George Harvey Vachell (1799-1839), who collected plants in China while the chaplain to the British East India Company in Macao.
- karroo – from the Karoo. The name, Karoo, was incorrectly spelt when the species was first described and cannot be corrected.
Common Names: Sweet Thorn (Eng), soetdoring (Afr), mooka (Nso & Tsw), leoka (Sso), singa (Tso), muunga (Ven), umnga (Xho)and umunga (Zul)
SAF Number: 172 Z Number: 189
- In cultivation a tree with rounded crown around 7m, but can reach 12m.
- In the wild it is often shrubby and invasive.
Size: 5 – 7m by 5 – 7m, may even reach 12 m
- Bright yellow, round ball- like flowers, to 1.5 cm diameter.
- In clusters at the ends of branchlets.
- Free flowering and spectacular in full flower.
Flowering Months: Nov – Feb (or even till Apr).
Fragrance: Flowers are sweetly scented.
- Leaves are bipinnate and feathery.
- They are arranged alternately on the branches.
- Leaves are dark green.
A Vachellia karroo in full flower is a wonderful spectacle.
- Straight, prominent white thorns are paired.
- Thorns grow from the base of the nodes.
- Older branches have fewer and less developed thorns.
- The pale brown, sickle-shaped pods have some constriction between seeds.
- Pods remain on the tree for quite a long time.
- The old bark is rough and fissured, dark brown to black.
- Young bark reddish brown with whitish to beige lenticels.
In the Garden:
- Suitable for larger gardens and large pavements as a shade tree, wind break, screening or feature tree.
- Because it is both extremely water-wise and cold resistant, it can be grown in areas where these factors limit choice of trees.
- A very good choice for larger wildlife friendly gardens, attracting insects, butterflies and birds.
- Good and popular bonsai subjects.
- Grows naturally in many different soil types, added nutrition will reward the gardener.
- A low maintenance garden tree.
- Plant in a cubic metre hole with lots of compost and some bonemeal can produce growth of a 1 m and more per year.
- May be pruned to shape.
Cold Hardiness: Very cold hardy.
The Vachellia karroo seed pods are quite long (up to 15 cm), narrow and sickle-shaped.
- Very drought hardy.
Light Requirements: Full sun.
Roots: Aggressive roots, do not plant too near paving, swimming pools, walls or buildings.
- Used by insectivorous birds for foraging and gleaning.
- Flowers and seeds are eaten by many birds (for a number of years a family of Brown-headed parrots visited the old nursery in Broadacres to feed on ripe Vachellia karroo and Combretum erythophylum seeds when they were ripe!).
- Thorny branches are favoured nesting sites of many garden birds.
- Bees are attracted to the flowers.
- In gauteng, a larval host to Thorn-tree blue, Velvet-spotted blue, Topaz-spotted blue, Black heart, Common Hairtail, Mashuna hairtail, Talbot’s hairtail, Black-striped hairtail, Eastern scarlet, Club-tailed charaxes
- Elsewhere possibly larval host to Mirza blue, Natal spotted blue, Little hairtail, Otacilia hairtail, Dark-banded scarlet, Purple gem and Brilliant Gem.
- An old Cape recipe of bark and leaves are used to treat dysentery and diarrhoea, the presence of acaatechin, quercetin and catechutannic acid suggest it will be effective.
- The gum, bark and leaves are used to treat colds, hemorrhaging and conjunctivitis.
- Gum is used to treat oral thrush.
The edible gum is sweet and often eaten by children.
A Vachellia karroo, Sweet Thorn, growing in the Karoo on the plateau in the Mountain Zebra National Park.
Poisonous: Not poisonous.
Notes of interest:
- Flowers, pods and leaves eaten by stock and game.
- The bark of younger branches is used to tan leather, giving the end product a reddish colour.
- The flowers provide nectar and pollen that make the trees popular with apiarists.
- The gum is edible and often eaten as sweets by children, and is used in confectionary and pharmaceutical production.
- Powdered root mixed with animal fat is used by some peoples in Nam to dress hair.
- Seeds roasted and ground have been used as a coffee substitute.
- WC, NC, a broad strip from south to north of Nam, eastern and north-western Bot, EC, KZN midlands, FS, NW,G, L, western M and south-west and central Zim.
- Northwards into Ang, Zam and Mal.
- Grasslands, fynbos, succulent-Karoo, Nama-Karoo, thickets, savanna-bushveld, savanna-woodland, savanna-Kalahari and savanna-lowveld.
Links to other members of the MIMOSOIDEAE (Thorn tree sub-family)
To go to the “plant blog” click on the plant name below the picture.
© Malcolm Dee Hepplewhite & Witkoppen Wildflower Nursery, (Text and Photographs) 2011 & 2018.