Vachellia robusta subsp robusta, the Robust Thorn-tree, is a small to medium upright decidious tree with a crown that is typically a lot narrower than it is tall. Its narrow upright growth and majestic stature make it a popular thorn tree for smaller to medium sized gardens.
Sub-family: MIMOSOIDEAE (Thorn tree family)
Name Derivation:
- Vachellia – named in honor of Rev George Harvey Vachell (1799-1839), who collected plants in China while he was the chaplain to the British East India Company in Macao.
- robusta – robust.
Common Names: Broadpod robust thorn, splendid thorn (Eng), enkeldoring (Afr), mooka (Nso), mvumbangwenya (Tso), mokhu (Tsw) muvumba-ngwena (Ven), and umngamanzi (Zul)
SAF Number: 183 Zim Number: 202
Form:
- A small to medium tree with an upright but slightly flattened crown.
- Has a very robust appearance.
Size: 4 – 6 m by 3 – 5m, may reach 10 m
Flower:
- Round balls.
- In clusters at the ends of branchlets.
- Free flowering and quite spectacular in full flower.
Colour: Cream to butter-yellow
Flowering Months: Aug – Oct.
Fragrance: Flowers are sweetly scented.
Foliage:
- Deciduous.
- Leaves are bipinnate, larger and more rounded than Vachellia karroo.
- Borne on woody cushions.
- Leaves are dark green.
- Long (4-6 but up to 10 cm) straight white thorns in pairs.
- Larger thorns may be furrowed along the top surface.
- Older branches have fewer and less developed spines.
Fruit:
- Pods are leathery or woody, fairly straight or thickly sickle shaped.
- There is no constriction between seeds.
- Pods remain on the tree for quite a long time.
Bark: Bark is dark brown, rough and fissured.
In the Garden:
- Well suited to medium and larger gardens and large pavements as feature trees.
- Because it is both drought 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.
- Should make good bonsai subjects.
- A water-wise choice.
Soil Needs:
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 a 1 m and more growth in a season.
- May be pruned to shape.
Cold Hardiness: Cold hardy.
Water Requirements:
- Drought hardy.
- Water-wise.
Light Requirements: Full sun.
Roots: Aggressive roots, do not plant too near paving, swimming pools, walls or buildings..
Birds:
- Used by insectivorous birds for foraging and gleaning.
- Flowers are eaten by Grey go-away birds and probably other birds as well.
- The thorny branches are used as nesting sites.
Insects and Butterflies:
- Bees and adult butterflies feed off the flowers.
- In Gauteng a possible larval host to Thorn-tree blue, Velvet-spotted blue, Topaz-spotted blue, Black heart, Mashuna hairtail, Talbot’s hairtail, Black-striped hairtail and Black-tipped scarlet
- Elsewhere possibly larval host to Mirza blue, Natal spotted blue, Little hairtail, Otacilia hairtail, Dark-banded scarlet, Purple gem and Brilliant Gem.
Poisonous: Not poisonous.
Notes of interest:
- Flowers, pods and leaves eaten by stock and game
- The flowers provide nectar and pollen to bees and other insects.
Natural Distribution:
- EC, KZN, northern M, G, L, NW, northern NC, eastern Bot, south-west and central Zim.
- Vachellia robusta subsp. robusta is endemic to southern Africa.
Natural Habitat: Grasslands, savanna-bushveld, and savanna-lowveld.
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