The caustic bush (Grevillea pyramidalis) is a small tree or shrub found only in Australia. Its white to cream or pale yellow flowers grow in clusters known as inflorescences, which in turn grow in groups called ‘conflorescences’ (2) (3). The pyramid-like shape of these groups of inflorescences gives the caustic bush its scientific name, pyramidalis (2).
The individual flowers of the caustic bush are irregular in shape, with four lobes (2) (4), and are only about three to six millimetres in length. The flowers of this species grow on tiny stalks, which measure up to two millimetres in length (2).
The leaves of the caustic bush are long and narrow, reaching lengths of up to 42 centimetres (3) and widths of just 0.5 to 2 centimetres (2). Sometimes the leaves are divided into a number of long, narrow lobes, which themselves may be further divided, and the leaf surface is occasionally hairy (2) (3). Three subspecies of caustic bush are recognised, Grevillea pyramidalis subsp. pyramidalis, Grevillea pyramidalis subsp. leucadendron and Grevillea pyramidalis subsp. longiloba, which vary mainly in the size and shape of their leaves (3) (5) (6) (7).
The caustic bush has small, sticky, egg-shaped fruits which measure 1.8 to 2.3 centimetres in length (2). As in other Grevillea species, each fruit is likely to contain one to two seeds (3).
- Also known as
- blister bush, caustic tree, maangga tree, turpentine bush.
- Height: 2 - 6 m (2) (3)
Caustic bush biology
Like other Grevillea species, the caustic bush has hermaphroditic flowers which contain both male and female reproductive parts (3) (4). This species typically flowers between May and July (2) (3). Little other information is available on the biology of the caustic bush, but in most members of the Proteaceae family the male parts of the flower become functional before the female parts, producing pollen which is picked up by pollinators such as birds or insects (4).
The fruits of the caustic bush have traditionally been used by Aboriginal people for tattooing, but have been known to cause caustic burns to the skin (8).
Caustic bush range
The caustic bush is found only in Australia, where it inhabits northern parts of Western Australia and the Northern Territory (2) (3).
Caustic bush habitat
The caustic bush usually grows in shrubland, low woodland or open, grassy woodland in sandy, gravelly or loamy soils (2) (3).
Caustic bush status
The caustic bush has yet to be classified by the IUCN.
Caustic bush threats
There is little information available on the conservation status of the caustic bush, but it is not currently reported to be threatened in Western Australia (2).
Caustic bush conservation
No specific conservation measures are known to be in place for the caustic bush at present.
Find out more
Find out more about the caustic bush:
More information on plant conservation in Australia:
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- Possessing both male and female sex organs.
- The reproductive shoot of a plant, which bears a group or cluster of flowers.
- A rich soil containing roughly equal proportions of clay, sand and organic matter.
- Animals that in the act of visiting a plant’s flowers transfer pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.
- A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
Tropicos (April, 2013)
FloraBase: The Western Australian Flora - Grevillea pyramidalis (April, 2013)
Wilson, A.J.G. (Ed.) (2000) Flora of Australia. Volume 17A, Proteaceae 2. Grevillea. ABRS/CSIRO Publishing, Melbourne.
Heywood, V.H. (1978) Flowering Plants of the World. Oxford University Press, Oxford.
FloraBase: The Western Australian Flora - Grevillea pyramidalis subsp. leucadendron (April, 2013)
FloraBase: The Western Australian Flora - Grevillea pyramidalis subsp. longiloba (April, 2013)
FloraBase: The Western Australian Flora - Grevillea pyramidalis subsp. pyramidalis (April, 2013)
Knight, R.J., McWilliams, T., Reeler, D., Whan, L. and Wood, F. (2011) An unusual cause of caustic burns. Medical Journal of Australia, 195(6): 355-356.