Brisbane Rainforest Action & Information Network


More of my favourite Plants

Kenneth McClymont

It would seern that the prediction I made in BRAIN 13 has come true- another article, featuring all the species of a local rainforest plant genus. Last time it was the mighty Canthiums but this time I would like to introduce, another lesser known though quite commonly occurring genus - the cool and charismatic Crotons!!

The genus name Croton is derived from the Greek word 'kroton' - tick, which refers to the resemblance of the seeds of this genus to ticks. There are approximately 750 Croton species worldwide with approximately 23 occurring in Australia (mostly all endemic). The local Crotons range in size from shrubs up to small trees. They have alternate leaves and bear unisexual flowers in racemes (an inflorescence of stalked flowers arranged along a single main axis). Fruit is a two-three celled capsule which splits open when ripe.
The rainforest cornmunities in the Brisbane region contain five described Croton species.

Thick-leaved Croton (Croton acronychioides).

Thick-leaved croton
Thick-leaved croton
The species name is derived from the similarity of the its leaves to those of the Acronychia genus).

This is a tall shrub or small tree to about 12 metres tall recorded from subtropical and dry rainforests from the Richmond River, NSW to Townsville, QLD, Thick-leaved Croton has branchlet ends covered with fine silvery brown scales. It bears racemes of fragrant creamy coloured flowers (June to November) followed by 3 lobed, egg-shaped red-brown capsule fruit (ripe November to February). This plant is usually found as a small understorey tree but can also be found growing on the edge of local rainforest remnants where it attractively displays it's dark green, shiny, slightly toothed foliage.

On our field trips to local scrubs this plant is often encountered and has become known to some of us as the 'banana cake tree' because of the identifying smell released by the crushed leaves. It is interesting to note that Floyd (1989) relates that the crushed leaves have a smell closer to 'fish oil', This plant would probably made an interesting and hardy addition to a home garden if it was commonly propagated.

Silver Croton (Croton insularis)

Silver croton
Silver croton
The species name is a Latin word referring to 'islands' as this plant was originally collected from a number of South Pacific islands.

This is a small tree growing up to about 15 metres tall recorded from subtropical and dry rainforests from the Blue Mountains, NSW to Cape Yorlc, QLD.

Silver Croton has silvery white branchlets covered by brown scales and as with several species of this genus the under leaf surface is also a distinctive silvery white colour. It bears racemes of silvery brown flowers (June to October) followed by silvery grey, globular capsule fruit (ripe November to January). Silver Croton can usually be found growing on the edge of rainforest and is a common small tree in dry rainforest regrowth. In full sun it has a tight, rounded crown with the silvery under leaf contrasting with the odd sprinkling of red/orange old and dying leaves.

Historically the bark of this plant was harvested for production of a distinctive reddish brown dye that was used to colour cotton and woollen fabrics. Interestingly, the injured bark of this plant produces a pleasant aromatic smell which resembles the odour of the West Indian Cascarilla Tonic-a cure all medicine which is extracted from a Caribbean plant closely related to Croton insularis. Another of the common names of Croton insularis is Queensland Cascarilla Bark.

This plant would suit a garden situation as it does not get too big, yet is relatively fast growing and very hardy. A good small shade or screening tree.

Narrow-leaved Croton (Croton phebalioides)

Narrow-leaved croton
Narrow-leaved croton
The species name is derived from the similarity of this plant to plants from the genus Phebalium)
This is a usually sparse shrub or small tree up to 8 metres tall recorded from dry rainforests and vine thickets between the Hunter River, NSW to NE QLD. It has a slightly pendulous branching habit and silvery white branchlet ends, with the underside of the leaves having a distinct silvery white colour. Narrow-leaved Croton bears racemes of small creamy brown flowers (April to December) followed by brown, hairy, 3 lobed capsule fruit (ripe June to December). Locally, this Croton is found to the west of Brisbane growing in quite dry and harsh conditions. I have observed it as a regrowth plant in semi-evergreen vine thicket (Rosewood scrub) along road reserves in the vicinity of Rosewood just outside Ipswich. This species would be a fast growing, interesting and very hardy garden plant, though unfortunately it is not commonly propagated.

This is a usually sparse shrub or small tree up to 8 metres tall recorded from dry rainforests and vine thickets between the Hunter River, NSW to NE QLD. It has a slightly pendulous branching habit and silvery white branchlet ends, with the underside of the leaves having a distinct silvery white colour. Narrow-leaved Croton bears racemes of small creamy brown flowers (April to December) followed by brown, hairy, 3 lobed capsule fruit (ripe June to December). Locally, this Croton is found to the west of Brisbane growing in quite dry and harsh conditions. I have observed it as a regrowth plant in semi-evergreen vine thicket (Rosewood scrub) along road reserves in the vicinity of Rosewood just outside Ipswich. This species would be a fast growing, interesting and very hardy garden plant, though unfortunately it is not commonly propagated.

White croton (Croton stigmatosus)

The species name is derived from Latin 'stigmata' for stigma and 'osus' for pronounced - this refers to the conspicuous stigma of the flower).
White croton is a large shrub or small tree growing up to 15 metres in height (though usually much smaller) recorded from subtropical and dry rainforests between the Hastings River, NSW and Imbil,Qld. This Croton has slender hairy and slightly scaly branchlets with leaves which are also slightly hairy on top and ensely covered wih silvery grey felt-like star hairs below. Racemes of creamy brown flowers (September to December) are followed by grey brown oblong to 3 lobed hairy capsule fruit (ripe December to February).
White Croton is quite uncommon locally. It would be a good plant for the home garden, its chief attraction being its soft, hairy silver foliage. young plants are fast growing and have much larger leaves than adult plants and would make interesting and attractive pot plants.

Native Cascarilla (Croton verreauxii)

Native Cascarilla
Native Cascarilla
The species name refers to J.P. Verreaux, a botanical collector from 19th century Tasmania).
Native Cascarilla is a large shrub or small tree usually growing up to around 6 metres in height (though it has been measured growing to 20 m!!) recorded from dry rainforest and along the interface between rainforest and eucalypt forest from Illawarra, NSW to Gympie, QLD and close to Darwin, NT. This Croton has relatively smooth branchlets with only a few scattered hairs and scales. Its leaves are soft, hairless, thin and green above and below and are distinctly finely toothed along the margins. Native Cascarilla bears small yellow-green flowers (November to January) which are followed by globular orange-brown capsule fruit (ripe March to July).

This Croton is similar to Croton insularis in that the older leaves on the plant turn orange before dropping and the bark emits a pleasant odour when injured. This plant is relatively commonly encountered in local rainforest remnants, especially along the exposed, sunnier edges of the forest where it acts as a pioneer species. It would be an easily grown addition to a home garden and would suit even a small yard as it does not get too big.

A few words on propagation
All of the local Crotons can be propagated from fresh seed or vegetative cuttings.

References

Floyd, A.G. (1989) Rainforest Trees of Mainland South-Eastem Australia. Inkata Press, Sydney.

Hauser, J.S. & Blok, J. (1998) Fragments of Green, an identification field guide for rainforest plants of the greater Brisbane region to the Border Ranges. Australian Rainforest Conservation Society, Brisbane.
(The diagrams have all been taken from `Fragments of Green' . Ed)