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Brillantaisia lamium

Description
 

Giant Tropical Salvia (Brillantaisia lamium) is an erect or sprawling herb to 150 cm high, sometimes scrambling over other vegetation. Its branches are 4-angled and have opposite leaves. The leaves have purplish petioles (stalks) up to 6 cm long in the lower parts of the plant but these become progressively shorter the higher in the plant one goes until they are eventually disappear and grade into bracts. The leaf blade is egg-shaped, 5-11 cm long and 2-7 cm wide; the margin is entire and the apex is either abruptly prolonged into a point or tapering to a point. There are white hairs present on both surfaces of the leaves but these are much denser below and may be quite sparse above (Sidwell 1998; Barker 2007, pers.comm.).

The inflorescence (a cluster of flowers) is at the apex of the stem and has a number of opposite side branches held perpendicular to the stem, somewhat like a candelabrum in appearance. The 2-lipped flowers are held at the end of these side branches. Flowering stems are visibly glandular hairy. The flower is a deep blue-purple, with a hood-like upper lip, often paler in colour, and a 3-lobed lower lip, both about 2 cm long. The upper lip is covered with glandular hairs. The erect seed capsule is 2-3 cm long and covered in black gland dots. There are 30-40 seeds per capsule, each one with a prominent supporting hook at its base. Seeds are disc shaped, flattened and covered with hairs which become mucilaginous on wetting (Sidwell 1998; Barker 2007, pers.comm.).

For further information and assistance with identification of Giant Tropical Salvia contact the herbarium in your state or territory.

Distribution:

Giant Tropical Salvia infestations are distributed in northern Queensland in the Douglas Shire around Whyanbeel, Cow Bay, Daintree River, Cape Tribulation, Shannonvale and Stuart Creek. In 2004 the Douglas Shire pest management plan identified Whyanbeel valley as highly infested, with small infestations occurring in Shannonvale, Crystalbrook, Mossman and Diwan/Cooper creek (Cunningham & Brown 2006). Since that time the species has also been found in Toowong/Mt Coot-tha area (Erhart 2006) and the Enoggera catchment (SOWN 2006) suggesting that it is a much wider threat than had originally been thought.

Habit:Shrub
Key points:
  • Giant Tropical Salvia (Brillantaisia lamium) is a known troublesome weed in tropical African crops such as Coffee, Oil-palm, Bananas and Rubber.
  • In Australia it has the potential to become a significant agricultural weed if it is allowed to spread.
  • Its preference is for wetter, and even shaded, areas where it will eventually form dense mats of vegetation because of its sprawling habit.
  • Plants are capable of spreading through vegetative means by the ability to form roots from any node and by root suckering.
  • Agricultural, gardening, mining and roadwork activity all have the potential to spread this species, whether by seed or plant fragments.
How it spreads:

Giant Tropical Salvia spreads by seeds and by stem fragments. There are about 30 seeds produced per fruit and these are flung out of the fruit explosively. The trigger for the fruit to explode may be wetting or drying but the exact cause is currently unknown. The seed is covered with hairs that in the dry state are pressed to the surface; on wetting these expand and exude a mucilage which probably glues the seed to a surface as it dries again. As with other Acanthaceae species, all nodes are capable of forming roots and so any stem fragments or sprawling plants are capable of taking root (Barker 2007, pers. comm.). It can disperse further than the local area by water and as contaminant of vehicles, machinery and nursery stock (Grice & Setter 2003).

Where it grows:

Giant Tropical Salvia 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 is able to grow in shade. It also has the potential to colonise disturbed areas such as roadsides, agricultural clearings and gaps in forests in the coastal areas of Queensland from Brisbane north (Weed Society of Queensland 2006). It is likely to also pose a threat to the wetter areas of the Northern Territory and the Kimberley region of Western Australia (Barker 2007, pers. comm.).

Flower colour:Blue, White, Purple
Distribution map:

http://www.weeds.org.au/cgi-bin/weedident.cgi?tpl=plant.tpl&state=&s=&ibra=all&card=H56 

Impacts:

Giant Tropical Salvia is one of seventeen sleeper weeds identified by the Bureau of Rural Sciences (following consultation with the Australian Weeds Committee) which could have nationally significant impacts on agriculture if allowed to spread.

 

Giant Tropical Salvia is a known troublesome weed forming dense stands beneath tropical African crops such as Coffee, Oil-palm, Bananas and Rubber. In Australia it forms dense stands along waterways, thus blocking access and competing with native vegetation. Its preference is for wetter and shaded areas where it will eventually form dense mats of vegetation because of its sprawling habit. It is likely to cause similar problems to those caused by Chinese Violet (Asystasia gangetica) (Barker 2007, pers. comm.).

Origin:

Giant Tropical Salvia is native to wet forest regions of Africa, from Sierra Leone on the west coast to Ethiopia, almost on the eastern coast and then south to Tanzania and northern Angola. It has naturalized in Kenya and is quite capable of forming weedy populations in cleared areas or in plantations in areas where it is native (Sidwell 1998).

History:

Giant Tropical Salvia has been known in Australia since 1996 when collections were first identified from the Innisfail area in Queensland. It has now spread in this area and in late 2005 it was reported from the Toowong/Mt Coot-tha area (Erhart 2006) and from the Enoggera catchment (SOWN 2006). Whether the initial introduction was as a garden plant is unknown, but this seems the most likely origin since it is an attractive plant with showy flowers. Many plants of the family Acanthaceae (which includes Giant Tropical Salvia) have been introduced as garden ornamentals in tropical areas and many are now becoming invasive (Meyer & Lavergne 2004; Barker 2007, pers. comm.).

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This database is designed to provide information, including biological and ecological, on invasive plant species that are on a national weed list, or are legislated against in a state or territory. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. For further information on the images contained in the database please contact the copyright owner. All images in the weed identification tool are managed by the Australian Plant Image Index (APII). Various copyright conditions apply for these images. For further information on the copyright conditions of images contained in the database please contact the APII at: photo@anbg.gov.au.