HLEM Environmental Management: Tetradenia riparia

Common names:

English: misty plume bush, ginger bush

Zulu: iboza, ibozane

The inflorescence of the male iboza plant

The inflorescence of the iboza plant

This plant was previously classified under the genus Iboza, which was derived from its Zulu name which refers to the aromatic qualities of the plant. Tetradenia means 'four glands' and riparia translates to 'growing on banks of rivers'.

Tetradenia riparia belongs in the mint and sage family Tetradenia riparia belongs in the mint and sage family Lamiaceae (which includes familiar culinary herbs such as thyme, sage and rosemary).

Tetradenia riparia is mostly found growing in warmer areas, on wooded hillsides, forest margins, dry wooded valleys usually growing amongst rocks.

Inflorescences

The inflorescences are branched, large bunches at the ends of the shoots. The individual flowers are about three millimeters in diameter and would appear in veins, the flowers range in color from white to lilac, and pink flowers are also found. Male flower spikes have more of the "mist" effect than the female flowers which tend to be more compact. Flowering occurs in wintertime, in South Africa from June–August when the plant is bare.

The flower of the male iboza plant

The type of display which you will get depends on whether you have a male or female plant. Male and female flowers are borne on separate plants in spikes which differ in size and shape. The male flower spikes in profusion create more of the "mist" effect than the female flowers which tend to be more compact.

The female flower of Tetradenia riparia

Leaves

The leaves are ovate-oblong to almost round or heart-shaped 30-180 x 30-140 mm, with irregularly, somewhat bluntly toothed margins.

They are a bright green colour and are slightly sticky to the touch due to the presence of whitish, velvety, glandular hairs on both surfaces.

Venation is indented above, prominent below, and they exude a strong, aromatic scent when handled.

Like many Lamiaceae species , the younger branches are distinctly four-angled in cross section

Medicinal uses

Tetradenia riparia is a medicinal plant known to the Zulu people as iBoza for which they have many uses for including the relief of chest complaints, stomachache and malaria. Inhaling the scent of the crushed leaves apparently also relieves headaches.

An essential oil extracted from its leaves has antimalarial properties.

Laboratory studies have shown that the herb contains ingredients that moderate the malaria-causing Plasmodium falciparum parasite. An extract from the leaves has also been found to inhibit bacterial growth.

I have found that a mixture of iboza and Artemisia afra wild wormwood leaves in boiling water when inhaled works well to relieve the symptoms of colds and flu.

Ecology

The pollen and nectar rich flowers attract many species of insects, in particular the Africa honeybee, Apis mellifera scutellata. This is an important forage plant for these bees in the Winter months.

Tetradenia riparia is associated with a moth (Trichoplusia molybdina) of the predominately night-flying Noctuid family.

Growing Tetradenia riparia

Tetradenia riparia is a rewarding easy to grow garden plant which is fast growing and will flower in its first year.

Plant iboza in full sun, except in very hot areas where midday shade or light shade may be beneficial.

Although Tetradenia riparia is usually found in the wild growing in poor soil in rocky localities requiring little water, in cultivation it will grow very rapidly if planted in well drained and well composted soil, at times too rapidly. To grow at its optimum, it needs to be well watered in the summer growing period but needs to be allowed to dry out and lose its leaves in winter for good flowering. rainfall areas, especially the bushveld regions. Because of this high degree of adaptability, it is also well suited to water wise gardens,

Tetradenia riparia must be pruned back hard after flowering to keep it neat and promote flowering.

Although iBoza is very drought resistant, in grows best if well-watered in the summer growing period, being allowed to dry out completely in autumn for best flowering which occurs in winter if it is leafless.

Roof Gardens

Tetradenia has proved to be a very drought resistant xerophyte when grown in poor shallow soils as a green roof plant.

Tetradenia riparia plants trialed as part of the Ethekwini Municipality Green Roof Pilot Project in early 2009 are still thriving in August 2024, over 15 years later.

Plants trialed as part of the Ethekwini Municipality Green Roof Pilot Project in early 2009 are still thriving in August 2024.

In addition, plants of iBoza have established themselves naturally in trials that I have conducted at my home. In both cases these plants have only received rainwater, never having been watered since their establishment.

This Tetradenia riparia established its self in a growing tray on my roof

Growing indoors.

After wind blown seed germinated in the pots of orchids that I am growing indoors I discovered that they grow very well indoors remaining evergreen making them very desirable indigenous greenery for indoors, however so far they have not flowered indoors.

Propagation

Tetradenia riparia is very easily propagated from cuttings, even from quite large truncheons which can simply be planted into the ground where one wants to grow them. They need do drying off or root hormones, just stick them into the ground and water occasionally until they have rooted and produced the first good growth thereafter, they can be watered normally. Just do not overwater them or they may rot. They can also be rooted in river sand, but this is probably unnecessary. To propagate Tetradenia in large numbers it is easiest to grow them from seed, but this requires an amount of propagation know how.