Vachellia tortilis, the Umbrella Thorn or Haak-en-steek, is the symbol of most peoples idea of the perfect African tree.
 

A medium to large, spreading ‘umbrella’ crowned tree, Vachellia tortilils is one of southern Africa’s most iconic trees. Besides its stunning shape, this thorn tree is widely used by both wildlife, stock and humans. Although fairly slow growing it is certainly worth growing in larger gardens, particularly in colder, drier regions.   

Family:                       FABACEAE             (Pea family)

Sub-family:               MIMOSOIDEAE   (Thorn tree sub-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.
  • Tortilis – ‘twisted’, referring to the twisted seed pods.
  • Heteracantha – ‘different thorns‘ refers to the hooked and straight thorns found on these trees.

Common Names:           Umbrella thorn (Eng), haak-en-steek (Afr), mosu (Nso & Tsw), umsasane (Swa & Zul)  and muunga-khanga (Ven)

SAF Number:                  188                         Zim Number:       208

Form:          A small to medium single stemmed tree.

Size:             5 -9m by 5 – 10m, may even reach 12 m

Flower:                          

  • Soft, ball- like flowers at the ends of branches.
  • Free flowering.

Colour                           White to cream.

Flowering Months:         Oct – Feb.

Fragrance:                      Flowers are sweetly scented.

Vachellia tortilis flowers are soft, white to cream, ball-like and sweetly fragrant.
The paired thorns of Vachellia tristis may both be straight, both hooked or one straight and one hooked.
Foliage:

Deciduous to almost evergreen.

Leaves are bipinnate and finely feathery.

Leaves are dark green.

Thorns:

The thorns are paired at nodes.

Pairs may be hooked or straight or even one hooked thorn and one straight thorn.

Fruit:

  •  The golden-brown pods are distinctly twisted and corkscrew noodle-like.
  • The pods may be single but are more often in clusters.
  •  Pods remain on the tree for quite a long time and do not open when ripe.

Bark:

  •  The bark is rough, brown to dark grey-brown.
  • Young trees have very distinct lenticels on stem and branches.

 In the Garden:

  • Suitable for larger gardens and large pavements as a shade and feature tree.
  • Because it is both drought and cold resistant, it can be grown in areas where these factors limit choice of trees.
  • A very good tree for wildlife friendly gardens, attracting insects, butterflies and birds.
  • Good and popular bonsai subjects.

Soil Needs:

  • Grows naturally in many different soil types, added humus and nutrition will reward the gardener.
The golden-brown pods are distinctly twisted and corkscrew noodle-like.
An example of an Umbrella Thorn, Vachellia tortilis, grown as a garden tree in Krugersdorp.
 Care:

  • A low maintenance garden tree.
  • Relatively slow growing, but good soil preparation will give 50 – 60 cm growth per year.
  • Pruning lower branches from the stem may also increase growth rate.
Vachellia tortilis growing in the Nama-Karoo near Postmasburg.
Cold Hardiness:              Very cold hardy.

Water Requirements:    Very drought hardy.            

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 and seeds are eaten by some birds including Brown-headed and Meyer’s parrots.
  • The thorny branches are favored nesting sites of many smaller birds, while white-backed vultures nest on the canopy.
Insects and Butterflies:

  • Bees, wasps and other insects feed off the flowers.
  • A larval host to Mashuna hairtail, and Talbot’s hairtail, both are occur in Gauteng.

Medicinal:

  • The bark is used for medicinal purposes.

 Poisonous:      May, at certain times, cause prussic acid poisoning (geilsiecte) in stock.

Notes of interest:

  • The gum that seeps from wounds to the bark is edible.
  • Flowers, pods and leaves eaten by stock and game.
  • The bark is an elephant favorite.

 

 

 

 

Vachellia tortilis growing in habitat in Mkuzi Game Reserve in KwaZulu-Natal.ings.

Natural Distribution:

  • Eastern NC, western FS, NW, G, M, northern KZN, Swa, L, a broad central strip from south to north of Nam, eastern and northern Bot, southern Zim and Moz.
  • North of our region into tropical Africa.

Natural Habitat:     Grasslands, Nama-Karoo, savanna-bushveld, savanna-Kalahari and savanna-lowveld.

 

Links to other members of the MIMOSOIDEAE   (Thorn tree sub-family)

© Malcolm Dee Hepplewhite & Witkoppen Wildflower Nursery, (Text and Photographs) 2011 & 2018.