Myoporum montanum, commonly known as waterbush or boobialla, is a shrub or small tree in the family Scrophulariaceae, native to Australia, New Guinea, and Timor.
Description
Myoporum montanum grows as a glabrous (hairless) shrub or small tree up to 8 metres (30 ft) tall. It is extremely variable in size, growth habit, and leaf form, with three primary forms recognised. The leaves are variable in shape but are most often thin, linear to elliptic, gradually tapering to the tip, with the mid-vein visible on the lower side only. They are usually about 45–100 mm (2–4 in) long and 5–21 mm (0.2–0.8 in) wide, glabrous, the same colour on both sides, and have smooth edges.
The flowers are sweet-scented, growing in clusters of one to five from the leaf axils on stalks 4.5–11 mm (0.2–0.4 in) long. There are five egg-shaped to triangular sepals with slightly papery margins. The corolla consists of five (rarely six) white or occasionally light pink or purple petals, which may have rows of purple spots. The petals form a tube 2–5 mm (0.08–0.2 in) long, with lobes about the same length, and the total flower diameter is about 6–8 mm (0.2–0.3 in). Flowering occurs mostly in winter and summer.
The fruit are smooth or slightly rough drupes, ovoid in shape, 5–8 mm (0.2–0.3 in) in diameter, and light purple, red-purple, or brown in colour. Remnants of the flower style point out of the fruit.
Taxonomy and naming
The species was first formally described by the Scottish botanist Robert Brown in 1810 in his work Prodromus Florae Novae Hollandiae. The specific epithet montanum is derived from Latin, meaning "pertaining to or growing on mountains."
It is difficult to distinguish from Myoporum acuminatum, and the ranges of the two species overlap. George Bentham considered M. montanum to be a variety of M. acuminatum. M. montanum has smaller, narrower leaves, and its sepals lack the translucent margins of those of M. acuminatum. The fruit of M. montanum is also pink or light purple compared with the dark purple or blue fruit of M. acuminatum.
Three forms are recognised (by Robert Chinnock):
- Type form – from the Blue Mountains, with narrow, linear leaves and small, faintly spotted flowers.
- Desert form – from arid areas of Australia, a large shrub or small tree with thick, elliptic leaves and prominently spotted purplish-red flowers.
- Tropical form – from northern Australia, New Guinea, and Timor, with thin leaves and very small, unspotted white flowers.
Distribution and habitat
Waterbush occurs in all mainland states of Australia, as well as in scattered areas in New Guinea, Irian Jaya, and Timor. It is very common in eastern Queensland, New South Wales, and eastern South Australia. It grows in a wide variety of ecosystem types, from mangrove swamps to rainforest to the Simpson Desert, on a wide range of soils. Its occurrence in many places is restricted to coastal regions, watercourses, and other locales with more reliable water supplies—an association that gave rise to the common name "waterbush."
Ecology
The fruit are a food source for a variety of birds, including emus, and were eaten by Aboriginal people. The food value of the fruits has been rated as low, and it is known that some members of the genus contain liver toxins. The flavour has been reported as "bitterly aromatic and salty sweet."
Use in horticulture
Waterbush is a hardy plant in cultivation and can tolerate drought. It is a useful screen plant in drier places and is readily propagated from cuttings. It tolerates most well-drained soils and situations, frost, and extended dry periods, as well as alkaline soils.
