Quick Facts

Quick facts

• Giant Tropical Salvia (Brillantaisia lamium) is a short lived large upright herbaceous plant (up to 2 m tall) with four-angled stems.
• 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.

What Does It Look Like?

What is it?

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.).

Flowers are formed as an inflorescence (a cluster of flowers) at the apex of the stem and have 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 lower lobe is usually curved downwards and has three small teeth at its tip (Biosecurity Queensland 2016).

The fruit is an elongated, cigar shaped (i.e. fusiform), capsule that turns from green to brownish in colour as it matures (Biosecurity Queensland 2016). 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.

Flower colour

Blue, White, or Purple

Growth form (weed type/habit)

Shrub

Where it currently grows? Preferred habitat

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.).

Are there similar species?

Because of its 4 angled stems and 2-lipped flowers Giant Tropical Salvia is most likely to be confused with species in the Lamiaceae family such as Salvia or Plectranthus or possibly with some members of the Scrophulariaceae family. It is immediately distinguishable as being from the Acanthaceae family by the presence of cystoliths (calcium carbonate crystals which appear as whitish elongated streaks) in the stems and leaves and by the presence of prominent hooks under the seeds in the fruit which remain visible in the fruit after the seed has been lost. The flattened seeds also possess mucilaginous hairs which expand when the seed is introduced to water, a characteristic not found in Lamiaceae or Scrophulariaceae species (Barker 2007, pers. comm.). It may also be confused with closely related species such as native hypoestes (Hypoestes floribunda), ribbon plant (Hypoestes aristata) and polka-dot plant (Hypoestes phyllostachya) (Biosecurity Queensland 2016).

Why Is It A Weed?

What are its 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.

Agriculture: 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.).

Native ecosystems: Giant Tropical Salvia colonises recently disturbed land and occasionally forms large, monospecific stands. In Australia it has demonstrated a propensity to form dense stands along waterways. It causes serious impacts to riparian areas and other habitats in coastal areas, where it out-competes the native vegetation and impacts upon wildlife by reducing natural sources of food and shelter (Biosecurity Queensland 2016).

How does it spread?

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).

What is its history in Australia?

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.).

How To Manage It?

Best practice management

There is no information documented on the control of Giant Tropical Salvia but it is likely that it will be similar, if not identical, to that for Chinese Violet (Asystasia gangetica), which is regarded as difficult to control.

Although viewed as a species where eradication is desirable it may not be feasible. Estimates for control of this species in 2006 where it was thought to be in 3 or 4 populations over 50 hectares were already given as $473,428 (Cunningham & Brown 2006). Eradication will be achieved by reduction of the seed bank and careful disposal of plants. Documentation of the biology of the species may provide some further insights into control measures.

Chemical control: Little is known about effective chemical control treatments. Advice could be sought from agencies that have had some experience in this area such as the Douglas Shire Council.

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Little is documented on the biology of Giant Tropical Salvia in Australia. Flowering is most common in summer but can occur all year round (Weed Society of Queensland 2006) with herbarium collections recording flowering from July to November. It grows quickly and is a prolific producer of the erect fruits (records of the State Herbarium of South Australia).

In the Brisbane area where the plant was not expected to be able to flourish, it has been found over-wintering in sheltered areas (Weed Society of Queensland 2006). The temperature tolerance of the plant needs to be established since it might be useful in providing a means of control. Further understanding of the plant and its biology will help in finding control measures.

Where Is It Found?

Which states and territories is it found?

QLD

What areas within states and territories is it found?

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.

Where does it originate?

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).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

Not declared in any Australian state or territory

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

YES

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Brillantaisia lamium

Other scientific names (synonyms)?

Leucorhaphis lamium Nees

Does it have other known common name(s)?

Tropical Giant Salvia, Brillantaisia