TREES     AQUATIC PLANTS     GRASSES

Large Fever-Berry

Croton megalabotrys

This is a common medium sized tree along water courses in Botswana. Typically it has a dense bushy growth.

The tree contains a number of toxins that can cause severe symptoms and even death if consumed in quantities.

Despite this it is browsed in small doses by a number of herbivores, most frequently by elephant. 

It can be used as a fish poison and to treat various sexually transmitted disease.

Sausage Tree

Kigelia africana

A medium to large and spectacular tree with a dense rounded crown.

Mostly found in open savannah and on river courses.

Being deciduous it does not offer much nutrition in winter and is occasionally browsed by elephant and giraffe in the growing season.

Kigelia cream (made from the skin of the  sausage like fruit) is commercial as a treatment of skin ailments and skin cancer.

The well known Botswana mokoro (dug-out canoe) was also traditionally made from this tree.

Knob Thorn

Acacia nigresens

A large deciduous tree with dark brown bark. It is commonly found along riverbanks.

Has a tap root that seldom goes deep into the soil, as water is readily available in its natural habitat. This shallow root system often causes the tree to be uprooted during heavy storms. The roots have nitrogen-fixing bacteria called ‘root nodules.’

The leaves are bi-pinnately compound.

 

Mopane

Colophospermum mopane

This deciduous tree’s size and height ranges from a scrub mopane to a medium-sized tree with a rounded crown and charcoal grey bark.

It has a tap root system.

The leaves are compound with a vestigial leaflet and two large leaflets on either side. They have high nutrient content, containing 12% protein. The dead leaves retain most of their nutrients and are a valuable source of food for mammals during the dry spring months in Botswana, particularly for buffalo and elephants. 

The insignificant, light green flowers are borne in summer. The seed is a flat pod.

Rain Tree

Philenoptera violacea

One of the taller trees in the Okavango savannah habitat.

It is characterised by its pale flaking bark and its leaning growth form with curved branches.

The large dark green compound leaves in this habitat can only be mistaken for the sausage tree which has a totally different growth form.

These trees have shallow roots and often fall over. They also shed huge branches and often collapse on buildings and tents.

The cross-grained wood is very strong and makes great handles for implements such as axes and pestle and mortar. 

If you can find one with a straight enough trunk they also make an excellent mokoro.

The pods are highly nutritious and make excellent browse for giraffe and other browsers that can reach.

Sausage Tree

Kigelia africana

A small deciduous tree with grey, fissured bark and a sparse, rounded crown.

It has as a tap root system.

The simple, shiny, asymmetrical leaves have three veins from the base and mildly toothed leaf margins. In late autumn, the tree loses its leaves.

The flowers are small, creamy-yellow and appear during summer.

The fruits were used as a coffee substitute. 

Has both straight and re-curved thorns. Some tribes believe that the straight thorn tells us to look to the future, whilst the hooked thorn reminds us to not forget the past. 

Baobab

Adansonia digitata

A large tree with a rounded crown and sparse leaf cover. The bark is grey and smooth, except where scarring has occurred. The trunk is abnormally large. This tree prefers hot, dry, open woodlands.

The leaves are palmately compound and clustered at the end of the branches.

Large white, drooping flowers appear in spring. The seed is encapsulated in crème-of-tarter , a chalk like substance.  The flowers are pollinated by bats. Elephants eat both the bark and the sapwood, causing extensive damage to these trees in the Delta.

Age estimates for the oldest baobab vary from 1000 to 6000 years, though the latter figure is highly unlikely. Carbon dating estimates an age of over 3000 years (Keith Palgrave).

Marula

Sclerocarya birrea

A medium/tall deciduous tree with relatively sparse leaf cover. The bark on the trunk peels off in large pieces.

It has a deep tap root.

The leaves are alternate and imparipinnately compound.

It has small yellow flowers appear from September to November. The fruit is juicy and creamy-yellow when ripe. The fruits make a potent drink, and the seeds in the kernel are much sought-after by people and by other animals. 

 Mokoros are made from the trunks of these trees.

Protection mechanisms include the release of tannins. As the tree matures, leaves out of reach of most browsers.

The Marula is found in both woodland and grassland habitats but is frost sensitive.

Jackal Berry

Diospyros mespiliformis

A tall (20 m) riverine tree with a dense crown. The dark bark gives the trunk an almost black appearance.

It has deep tap root system.

The leaves are simple and alternate along the branches. The dark green foliage provides excellent shade.

The creamy-white flowers appear in October and November. The fruits are tasty and make a strong beet when fermented.

Local people of the Delta use these trees to make mokoros (traditional dugout canoes). 

Protective mechanisms include the production and release of tannins. The leaf-bearing branches of mature trees are out of reach of browsers.

The jackal berry favour riverine forests and are often found growing alongside termite mounds.

Broad-leafed Pond Weed

Potamogeton thunbergii

Grows along the edges of channels and becomes partially submerged during flood waters.

The leaves are spear shaped.

The insignificant creamy flowers are borne on long, erect spikes.

It is common throughout the Okavango where you find floodplains.

Yellow Ottelia

Ottelia muricata

A perennial plant found in the channels of the Delta, often forming dense clumps.

They have large obovate leaves.

The bright yellow flower floats on the surface.

The base of the flower has a swollen, soft-spined sheath around it. The water stored in the flower head is used by local people of the Delta as an eye drop.

Bladderwort

Utricularia gibba

An aquatic, carnivorous herb that has evolved as an insectivore to compensate for the lack of nutrients in the water.

The roots have bladders that trap small insects. The bladders are under negative pressure. When prey pushes past the roots, trapdoors are set off, sucking the prey item into the bladder.

The flowers are golden-yellow and flower year round.

 
 

Saw-tooth Love Grass

Eragrostis superba

Easily identified by the large seed with overlapping florets.

It is one of many Eragrostis species in the Okavango Delta and like most Eragrostis, it has a medium to low palatability as a grazing grass.

Red-top Grass

Melenis repens

A very easily recognised grass. It grows in dense clusters and the reddish feathered inflorescences stand out from a distance. It grows on sandy soils and has a medium-low grazing value.

Digit Grass

Digitaria eriantha

This grass gets its name from the finger like appearance of the panicle.

There are several other species with a similar inflorescence so care should be taken in identification

It is a reasonably good grazing grass with a medium to high palatability.

Couch Grass

Cynodon dactylon

A short grass growing in huge dense stands. It is a very resilient grass and persists on roads with heavy traffic long after other grasses have perished. 
It is reasonably palatable and increases with overgrazing.

Spear Grass

Heteropogon contortus

A relatively tall grass with a high leaf production. The single tight raceme often intertwines with plants forming clusters.

It has a medium palatability and increases when overgrazed.

It can be very unpleasant to walk through and gets its name from the spear-like seeds that push through socks and trousers alike. 

Buffalo Grass

Panicum maximum

This tall perennial grass is easily recognised by its large, open inflorescence and tall growth form reaching up to 2m in height.

Favours shady habitat and is a good grazing grass that decreases with overgrazing.

It is also an excellent food source for small seed-eating birds like waxbills.

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