BRILLANTAISIA

November 2005    (Brillantaisia lamium)

Distribution

Brillantaisia (Brillantaisia lamium) was first recorded as naturalised in 1996 near Innisfail in northern Queensland. It has since been found in other parts of northern Queensland, and from Toowong and Mt. Coot-tha in Brisbane in south-eastern Queensland.

Additional infestations have recently been detected along Enoggera Creek in the northern suburbs of Brisbane.

Origin

Brillantaisia is native to the central and western parts of Africa.

Habitat

This species prefers damp habitats and in Australia it has been found growing along the edges of waterways, in orchards, in nurseries and around sugarcane plantations. It also has the potential to colonise disturbed areas such as roadsides, agricultural clearings and gaps in forests in the coastal districts of Queensland.

Impact

Brillantaisia is known to be weedy in western Africa, where it colonises recently disturbed land and occasionally forms large, monospecific stands. It also forms a dense understorey within plantation crops such as oil palms, cocoa, coffee and bananas. In Australia it has also demonstrated a propensity to form dense stands, particularly along waterways.

It has been mainly seen as a threat to the tropical parts of northern Australia, however the dense stands that have been found growing in sheltered areas in the middle of winter in south-eastern Queensland suggest that it might also be a significant threat in sub-tropical regions.

Description

This large branched herb usually grows 50-150 cm tall, but may occasionally reach up to 2 m in height. It is a short-lived (i.e. annual) plant with an upright (i.e. erect or ascending) habit.

Its stems are somewhat hairy, square in cross-section, and bear leaves in pairs. The leaves (up to 15 cm long and 7 cm wide) are usually borne on relatively long stalks (i.e. petioles), though the uppermost ones may be almost stalkless. They are sparsely covered with long soft hairs on both surfaces and are egg-shaped (i.e. ovate) or heart-shaped (i.e. cordate) in outline.

The violet or purple flowers (20-30 mm long) are borne in loose, branched clusters at the tips of the branches. The flowers are fused at the base (i.e. into a corolla tube about 6 mm long) and separate into two lobes (i.e. they are two-lipped). The upper lobe is hooded, while the lower lobe is usually curved downwards. Sticky hairs are usually present on the inflorescence branches and on the outer surface of the petals. Flowering can occur all year round, but is most common during summer.

Reproduction and Dispersal

Brillantaisia reproduces by seeds and also occasionally via stem fragments that can take root in damp environments. The fruit is an elongated capsule (about 30 mm long) that usually contains about 40 seeds. These seeds are explosively released from the fruit when mature.

Legislation

This species is currently not declared in Queensland. However, it has been listed by the Commonwealth Department of Agriculture, Fisheries and Forestry (DAFF) as one of seventeen candidate sleeper weeds.

Further Information

Pacific Island Ecosystems at Risk (PIER), Plant threats to Pacific ecosystems: http://www.hear.org/pier/species/brillantaisia_lamium.htm. US Department of Agriculture, Forest Service.

Weeds Australia. Weed Identification - Brillantaisia. http://www.weeds.org.au.