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.

Vachellia robusta subsp. robusta, the Broadpod Robust Thorn-tree is an attractive small to medium size thorn-tree that is suitable for smaller gardens.
Family:                       FABACEAE        (Pea family)

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

Vachellia robusta subsp. robusta is a small to medium tree with an upright but slightly flattened crown.
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.
The leaves of Vachellia robusta subsp. robusta are bipinnate and borne on woody cushions.
Vachellia robusta subsp. robusta has long, straight that are paired, but older trees tend to have fewer and shorter thorns.
The pods of Vachellia robusta subsp. robusta are quite woody and remain or the tree for a long time before splitting to release the seeds.
Thorns:

  • 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.

 Soil Needs:

Grows naturally in many different soil types, added nutrition will reward the gardener.

 Care:

  • 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.    

Light Requirements:     Full sun.

Like all Vachellias, the Broad-pod Robust Thorn-tree has round, ball-like flower spikes.
A Grey Go-away-bird eating Vachellia robusta subsp. robusta flowers in our garden in North Riding.
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.
Medicinal:                         No reference to medicinal uses.

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.

Vachellia robusta subsp. robusta is a good alternative thorn-tree to the Vachellia karroo in a small to medium sized garden.
Links to other members of the MIMOSOIDEAE   (Thorn tree sub-family)
© Malcolm Dee Hepplewhite & Witkoppen Wildflower Nursery, (Text and Photographs) 2011 & 2018.