''Androstachys johnsonii'', the Lebombo ironwood, is a medium-sized

Afrotropical The Afrotropical realm is one of Earth's eight biogeographic realms. It includes Africa south of the Sahara Desert, the majority of the Arabian Peninsula, the island of Madagascar, southern Iran and extreme southwestern Pakistan, and the island ...

tree species, and the sole member of the genus ''Androstachys'' in the Picrodendraceae. It is slow-growing, evergreen to deciduous, and

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

, with flowers that are wind-pollinated. It is native to southeastern Africa and Madagascar, where it generally occurs gregariously on rocky hillsides, particularly in hot and dry situations. It produces a hard, durable wood which is of economic interest. Its specific name commemorates W. H. Johnson, a 19th-century Director of Agriculture in Mozambique. Four related species which are native to Madagascar, are usually placed in genus ''

Stachyandra ''Stachyandra'' is a plant genus in the family Picrodendraceae first described as a genus in 1990.Radcliffe-Smith, Alan. 1990. Notes on Madagascan Euphorbiaceae, III. ''Stachyandra''. Kew Bulletin 45(3): 561–568 The entire genus is endemic to ...

''.

Uses

Its timber is of economical interest. The wood is extremely hard and durable. It is widely exploited in southern Mozambique, where it is known as ''simbirre''. Here it is used for flooring, for which it is well-suited, and is commonly traded for pillars of huts and fences. South African tourist operators in Mozambique used it extensively for building structures near or in sea water. It is also traded as mecrussé in Mozambique, but rarely so, presumably due to a lack of supply.

Range and habitat

Within southern Africa, it occurs in Limpopo Province,

Mpumalanga Mpumalanga () is a province of South Africa. The name means "East", or literally "The Place Where the Sun Rises" in the Swazi, Xhosa, Ndebele and Zulu languages. Mpumalanga lies in eastern South Africa, bordering Eswatini and Mozambique. It ...

and

Eswatini Eswatini ( ; ss, eSwatini ), officially the Kingdom of Eswatini and formerly named Swaziland ( ; officially renamed in 2018), is a landlocked country in Southern Africa. It is bordered by Mozambique to its northeast and South Africa to its no ...

. It is commonly found at altitudes up to 1000 m. It forms dense shrub-like thickets and thrives in hot and dry climates with well drained soils, especially on rocky hillsides or along seasonal watercourses.

Description

It is described as a medium-sized, evergreen tree growing up to 20 m high. It is characterised by a roug
bark
with a whitish, woolly, hair like covering on the new growth. The leaf blades are 3–9 × 2–7 cm and are oppositely paired at right angles. They are ovate to heart-shaped with both the apex and base rounded. The upper surfaces are shiny and are a green to blue-green color, beneath the surface is covered in dense, white, woolly hairs.

Flowers

Flowering time is October–November. Flowers axillary, unisexual and vary in both arrangement and appearance. Male flowers are yellow and are arranged in a 3-flower cluster up to 3 cm long. Central flowers are longer than the laterals with their pedicel being 1–1.3 cm long versus the lateral length of 5–6 mm.

Sepals A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...

; greenish petals that the form the

calyx Calyx or calyce (plural "calyces"), from the Latin ''calix'' which itself comes from the Ancient Greek ''κάλυξ'' (''kálux'') meaning "husk" or "pod", may refer to: Biology * Calyx (anatomy), collective name for several cup-like structures ...

of the flower differ in number; 5 in central flower and 2-3 in laterals. The bulbous base or

receptacle Receptacle may refer to: Biology * Receptacle (botany), a plant anatomical part * Seminal receptacle, a sperm storage site in some insects Electrical engineering * Automobile auxiliary power outlet, formerly known as ''cigarette lighter recep ...

of flower from which its organs grow are 2 cm long in central; 1.5 cm in laterals. Stamens up to c. 50 in central c. 35 in lateral, filaments of lowest stamens up to 1 mm long,

anthers The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...

3 x 0.5 mm covered in fine silky hairs in early development and then smooth, lacking hairs with maturation. Yellowish

thecae In biology, a theca (plural thecae) is a sheath or a covering. Botany In botany, the theca is related to plant's flower anatomy. The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a comm ...

. Female flowers are yellow and are at the end of a long, white hairy stalk. Pedicels are 1–1.5 cm long, extending to up to 3 cm long in fruit;

sepals A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...

7–8 × 2–2.5 mm and are an ovate-leaf shape, blunt tapering or sometimes split at apex, minutely ruffled with fine hairs on edge and base; otherwise smooth.

Ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

is c. 3 mm in diameter, oval in shape, densely covered in fine white woolly hairs. Styles c. 7 mm long with fine hair covering, stigmas are globe shaped.

Fruit

The fruit is bright green at first and ripens to a light yellow or reddish brown and is covered in fine bristle-like hairs. It is a 3-lobed capsule, 8–10 x 12–13 mm in size, and is easy to detach. The

seeds A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm pl ...

are chestnut brown in colour, with a long, shallow, linear ridge. Their dimensions are 6.5–7(8) x 4.5–5(6) x 2–3 mm.

References