© E Schmidt

Lebombo-ironwood is an evergreen tree which occurs in hot savannas; it is reputed for its hard- and long-lasting wood. Many strong structures around the region where it occurs are built from it and it has even been used to build bridges. The species makes an attractive ornamental with its attractive, deep green, rounded leaves, which are white on the underside.

Description
Evergreen to deciduous, medium-sized tree that grows up to 20 m tall. This tree grows well in rocky areas. The leaves are dark green, round with a greyish white underside. The flowers are yellow with petals absent.

© E Schmidt

It bears yellowish to brown, 3-lobed fruit.

© E Schmidt

Conservation status
Androstachys johnsonii has been largely exploited in the areas where it occurs and has been reported to have been widely exploited in Mozambique in 2005; since it is a slow-growing tree, the recovery of the individuals that have been lost, has been slow. It has been listed under LC (Least Concern) category in the Red Data List.

Distribution and habitat
This genus contains four other species that have been identified as coming from Mozambique. It is distributed in the southern parts of Africa, through Mozambique, Swaziland, Zimbabwe, Malawi and Madagascar, as well as South Africa where it can be found in Limpopo Province, and the Lebombo Mountains in KwaZulu-Natal.

Derivation of name and historical aspects
Androstachys in Greek means ‘with male flowers in a spike' and the specific epithet johnsonii comes from W.H Johnson, the Director of Agriculture in Mozambique in 1875. This tree was previously part of the Euphorbia family, Euphorbiaceae, but was listed as Picrodendraceae in 2003.

Ecology
Androstachys johnsonii likes to grow in colonies in rocky hillsides. It enjoys well-drained soils with hot, dry conditions. The flowers on the trees are pollinated by wind. The fruits are eaten by birds, antelopes and squirrels and then distributed.

Uses and cultural aspects
This tree has been over utilised because of its hard, durable wood used for different purposes such as flooring, structural support for houses, as well as for building bridges. The leaves are browsed by livestock; bees collect the nectar from the flowers, but it has been reported that the nectar from the flower is poisonous.

Growing Androstachys johnsonii

This tree can only be grown from seeds that germinate readily on the ground under adult trees. This is a slow-growing tree and takes years for the tree to reach its mature stage. There are no reports in the literature of other methods of propagation. Trees are easily grown in gardens outside of its natural range, although slow growing. They should be planted in full sun to semi-shade on a well-drained, warm slope; the species can withstand moderate frost, but should be protected from black frost and when young.

References and further reading

• A.P.G. [= Angiosperm Phylogeny Group] II. 2003. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Bot. J. Linnean Soc. 141: 399-436.
• Schmidt, E.,Lotter,M. & McCleland, W. 2002. Trees and shrubs of Mpumalanga and Kruger National Park. Jacana, Johannesburg.
• http://www.prota4u.org/protav8.asp?g=psk&p=Androstachys+johnsonii+Prain
• http://redlist.sanbi.org/species.php?species=596-1