Acronychia acronychioides (Rutaceae)

Acronychia acronychioides DSC_0608 (2)

This endemic shrub/tree species is commonly known as the White Aspen, which makes little sense as it is nothing close to being an aspen (which belongs to temperate trees of the genus Populus). But delve a little into the scientific naming of this species and we open a can of worms.

The species was first named by Ferdinand von Mueller as belonging to the genus Euodia in 1864. And Mueller gave it the specific epithet “acronychioides“, in allusion to how this species looks like a plant from the genus Acronychia.

One year later in 1865 he described another plant (which was of the same species) and this he called Acronychia melicopoides. I am not sure if Mueller was aware that the plant he was describing was from the same species but now he was certainly clearer that this specimen was a species of Acronychia. Still he felt it must look like something else, a species of Melicope, hence the specific epithet “melicopoides“.

Over a century later. taxonomist Thomas Gordon Hartley finally decided that the plant should be named Aconychia acronychioides, the Acronychia that looks like an Acronychia, putting an end once and for all (I hope) to the rather absurd naming history of the species.

Acronychia acronychioides DSC_0620 (7)

Acronychia acronychioides DSC_0620 (1)

Acronychia acronychioides IMG_6918 (1)

Posted in Endemics, Habitat - Rain forest, Lifeform - Trees & Shrubs, Rutaceae (Citrus family) | Tagged , , , , | Leave a comment

Backhousia tetraptera (Myrtaceae)

Backhousia tetraptera

By world standards the rainforest flora of Australia is rather well described, but there are still species out there to name and discover. Such was the case with a mystery tree found at Mt Stuart near Townsville. Thus far the population at Mt Stuart is the only one known.

The species is a tree between 5 and 12 metres tall, with multiple trunks with a mottled flaking bark. The bark has a range of colors including grey, grey-brown and/or pink colouration, which gives the plant an appearance of a large Gossia sp.

Finally in 2012 the species of myrtle was formally described by Prof. Betsy Jackes and colleges. The species is so named because of the clustered and distinctive pink-white capsular fruits with four wings (hence “tetraptera”).

I’ve only had the pleasure of seeing the species as a cultivated specimen but I hope to one day see it in the wild.


Harrington MG, Jackes BR, Barrett MD, Craven LA, Barrett RL. 2012. Phylogenetic revision of Backhousieae (Myrtaceae): Neogene divergence, a revised circumscription of Backhousia and two new species. Australian Systematic Botany 25(6) 404-417

Posted in Endemics, Habitat - Rain forest, Lifeform - Trees & Shrubs, Myrtaceae (Myrtle family) | Tagged , , , | Leave a comment

Savoring the Sapindacean Symphony

Jagera pseudorhus DSC_0523 (2)Sapindaceans. Or so I feel they deserve to be called. Many know them as the family of plants, the Sapindaceae, that gives us rambutans, lychees, longans, ackees, tamarinds, tuckeroos. What would tropical rainforest be without them. They may not be the tallest of trees, but collectively their contribution to tropical rainforest diversity and ecology ranks among the laurels (Lauraceae) and myrtles (Myrtaceae). In the Australian tropical rainforest at least, the Laurelian-Myrtacean-Sapindacean trinity rules.

The symphony of Sapindacean form is dramatic. As a family, the diversity of leaf and fruit forms amongst Sapindaceans are astounding. So much colour. So much texture. The Sapindacean symphony is well worth learning.

It turns out that spotting a Sapindacean in the rainforest is not difficult at all. One of the key characters of Sapindaceans can be very easily remembered by remembering their family name, SaPINdaceae. In most species, there is a very obvious “pin” at the tip of the compound leaf.

Sarcotoechia villosa DSC_0396 (8)
The SaPINdacean PIN

The next very distinctive feature is that these compound leaves are almost always alternately arranged along the twigs.

And finally, the absence of stipules is another distinctive feature.

Now identifying species is a different matter altogether, and an immensely enjoyable one. Sapindaceans vary so much in leaflet shape, size, number, colour and texture, leaflet venation, leaflet margin features, leaflet accessory features that they never fail to entertain (and exasperate).

It is not easily to group genera of Sapindaceans by leaf features but some species do fall into somewhat readily recognizable groups.

Lets start with the BIG. Not in terms of tree size, but leaflet size. Some Sapindaceans have astonishingly large compound leaves (and leaflets). One of the wonders of the tropical far north must be to see Bernie’s Tamarind (Diploglottis bernieana). But Mischocarpus grandissimus is on par.

Diploglottis bernieana
Diploglottis bernieana is now widely planted locally. It is not apparent here but those leaflet are a whooping 30cm x 20cm.

Mischocarpus grandissimus
Mischocarpus grandissimus have large almost dinner-plate sized leaflets

Some Sapindaceans have leaves with glaucous undersides. The cultivated longan (Dimocarpus longan) is a good example but native examples are Castanospora, Cnesmocarpon, Dimocarpus, Guioa spp.

Castanospora alphandii
Castanospora alphandii is a prime example of a species with very glaucous leaflets.

Cnesmocarpon dasyantha DSC_0030 (1)
Cnesmocarpon dasyantha also has rather glaucous leaflets.

Many Sapindaceans have distinctively toothed leaflets. Examples are Alectryon tomentosus, some Cupaniopsis spp. Jagera sp., some Lepiderema spp. some Sarcotoechia spp. etc.

Jagera pseudorhus Cattana DSC_0048
Jagera pseudorhus, a common tree often found near the coast and slightly drier rainforest types. “Jager” is jagged.

In a number of species, the leaflet stalks are absent or reduced, often into a bulbous knob. Guioa spp are prime examples, but this also happens with some Sarcotoechia.

Sarcotoechia villosa DSC_0396 (2)
Sarcotoechia villosa with opposite leaflets with bulb-like stalks.

In some species, the rachis of the leaflets are winged – that is, the part of the leaf that holds the leaflets have wing-like bits of leaf lamina. This happens very conspicuously with Harpullia frutescens and H. rhyticarpa. The weird and wonderful savanna-occurring Atalaya also has this feature.

Harpullia rhyticarpa DSC_0870
Harpullia rhyticarpa has a winged rachis

Many Sapindaceans are spectacularly hairy. The different extent of hairiness and depth of hair colour give the Sapindacean symphony texture. In Diploglottis there is a great multitude of shades of leaf colour because of these hairs. Guioa lasioneura and Mischocarpus lachnocarpus are have nice and hairy leaves.

Diploglottis macrantha
Diploglottis macrantha has somewhat dull looking leaves

Diploglottis smithii DSC_0198
Diploglottis smithii looks silvery on the underside, partly due to the hairs.

But of course, many Sapindaceans are bald, and shiny too, and infuriatingly within some of those genera already mentioned.

Dictyoneura obtusa DSC_0146 (1)
Dictyoneura obtusa is bald and shiny. Note the bulb-like leaflet stalks

!Beware the Sapindacean imitators

Cardwellia sublimis JCU DSC_0186
The Silky Oak (Cardwellia sublimis), yes sublime in its own right, is a Sapindacean imposter! It has alternate compound leaves, and even something like a PIN at the end of the compound leaf rachis. The bronzey-silvery sheen should be a good distingushing feature.

Dysoxylum latifolium DSC_0552 (14)
Dysoxylum latifolium also has the naughty habit of imposing as a Sapindacean. Can’t help there with distinguishing feature.

Closing remarks

The Sapindacean Symphony is playing at a rainforest close to you. Don’t miss it.

Posted in Habitat - Rain forest, Learning Plants, Lifeform - Trees & Shrubs, Sapindaceae (Rambutan family) | Tagged , , , , , , , , | Leave a comment

Sizing up the Syzygiums

A wander through the tropical forests of North Queensland, and for that matter any tropical forest in the Southeast Asian and Pacific region, would be so much more richer an experience if one could recognize or at least tell between the multitude species of lily pillies and satinashes (Syzygium spp.) that inhabit these forests.

If eucalypts dominate the vast open woodland vegetation of Australia, Syzygium could be considered its rainforest counterpart, at least in terms of the number of species found in the tropics (100 spp.). Both eucalypts, Syzygiums and allied genera are from the large Myrtle family. So it turns out that Australia really specialises in Myrtles. As a group also, Syzygium must play an immensely importance role to the ecosystem of the rainforest by providing food. Most of the species of Syzygiums are probably edible (…most really are just edible).

The difficulty of identifying Syzygiums without fruit (or even with) is well known among botanists. Any botanist with a modicum of modesty would admit to countless nightmares of green-jobs with no other than opposite leaves. My utmost respect goes to Bernie Hyland who did the most comprehensive revision work on the Syzygiums of North Queensland.

But even without the eye of a fully fledged taxonomist we can still try to recognize at least a selection of the more common or distinctive species by leaf whispering (here taken to mean by just knowing how the leaves look like).

So here are a few features:

Syzygium papyraceum DSC_0271 (2)
Syzygiums have opposite leaves, without any discernible stipule or stipule scar.

Syzygium alatoramulum__DSC3388
– The leaves typically have an intramarginal vein.

– The leaves usually have a thick or leathery texture

Syzygium bamagense DSC_0319 (4)
Oil dots are present in the leaf lamina. Sometimes this is hard to see for the very thick-leaved species.

– the leaves of many species are a deep dark green

Having said this I must clarify that these feature apply for most species in the related Myrtaceae genera Backhousia, Eugenia, Decaspermum, Gossia, Psidium, Pilidiostigma, Rhodamnia, Rhodomyrtus, Uromyrtus, etc., but members of many of these genera have some subtle distinguishing features themselves which I will go into later in another post.

So here is an overview of some groupings of selected species with potentially easily recognizable leaf characteristics.

Building on the typical thick-leaf feature of Syzygium leaves, some species have a somewhat shiny underside, with the nerves not very obvious. Examples are S. papyraceum and S. johnsonii. In the case of S. kuranda, S. hemilampra and S. fibrosum, the leaves are not shiny underneath but the leaf blades are rather leathery.

Syzygium papyraceum DSC_0271 (3)
Syzygium papyraceum have thick leaves with shiny undersides, but is best identified in the field by the orangey papery shedding bark.

Syzygium johnsonii DSC_0036 (1)
Syzygium johnsonii with shiny leaf undersides. This species also has a rather strong distinctive “lolly” smell emitted when leaves are crushed

Syzygium branderhorstii DSC_0484 (2)-001
Syzygium branderhorstii has a rather green underside, not so different in shade from the upperside.

Some Syzygiums have twigs with angular cross-sections (especially near the newest leaves are borne) or twigs with flanges. Syzygium australe is a common example. Flanged twigs also occur on the often coastal growing S. angophoroides, which in addition has a habit of the leaves that turn red or orange before shedding. The character of having flanged twigs is strongly expressed in S. alatoramulum, S. apodophyllum and S. hedraiophyllum and S. trachyphloium.

Syzygium alatoramulum__DSC3387
Syzygium alatoramulum has strongly flanged (or winged) twigs

Syzygium trachyphloium DSC_0694 (4)
Syzygium trachyphloium is another example of a species with flanged twigs

Some species have small cute leaves with extended pointy tips. Examples are S. luehmanii, S. canicortex and S. dansiei. The related genus Decaspermum humile can look very similar but the leaves in this species has a raised midrib on the leaf upperside. Uromyrtus also looks similar, but often have hairs.

Syzygium luehmanii DSC_0098 (3)
Syzygium luehmanii is a widely cultivated species, probably because of their attractive smally cutey pointy shiny leafies.

Many species of Syzygium can be distinguished by their venation, and how far one takes this will be a testimony to one’s “monomaniacism”. The common cultivated S. cormiflorum has a certain ladder-like vein pattern obvious on the leaf underside. This venation feature can be useful for recognizing some Syzygiums in the field in a sterile state. S. sharoniae, a species more or less restricted to the Daintree region, has venation pattern also resemble S. cormiflorum, but has a somewhat slight silvery sheen, and smaller leaves. S. monospermum and S. erythrocarpum, probably best identified by their fruits borne on stems, have similar ladder-like patterns with S. cormiflorum. These two species, S. monospermum and S. erythrocarpum, often have have cordate leaf bases.

Syzygium cormiflorum DSC_0519 (1)
Syzygium cormiflorum with ladder-like leaf venation.

Syzygium erythrocalyx DSC_0177
Syzygium erythrocalyx with a ladder-like secondary venation.

Syzygium sharonae nearNoahBeach DSC_0670
Syzygium sharoniae has a somewhat shiny underside with a ladder-like secondary venation.

Syzygium tierneyanum IMG_7711
S. tierneyanum has a similar sort of vein pattern but has narrow leaves. Syzygium glenum is a very restricted species endemic to Cape Tribulation and so are probably not going to be seen by most but the species has a superficially similar venation pattern to S. tierneyanum.

On the feature of “longish” leaves, there are a number of species that look rather alike.

Syzygium wilsonii (top) and S cryptophlebium (bottom) DSC_0548 (5)-001
Syzygium wilsonii (top) and S cryptophlebium (bottom) leaf undersides. These two species are two very frequently cultivated and reasonably common species that one may encounter.

Syzygium glenum Cooper Creek DSC_0255 (2)
Syzygium glenum is a rare species with longish leaves

Some species clearly have two intramarginal veins. An example is Syzygium graveolens, which can be distinguished by the dark red-brown trunk. S. divaricatum has very similar leaves. Syzygium gustavoides has a very strong two intramarginal veins with a very distinctive pattern of venation between the inner and out intramarginal veins.

Syzygium divaricatum WinfieldPark DSC_0710 (6)
Syzygium divaricatum leaves. The photo is intentionally darkened to highlight the venation. Note the appearance of two intramarginal veins. This particular species also has rather leathery leaves and very thick leaf stalks.

Most Syzygiums have entire leaf margins (i.e. bearing no teeth), but when the “entire leaf margin” rule is broken, the species can be identified almost instantly. Syzygium sayeri is one such species that breaks the cardinal rule of the Syzygium alliance of being toothless.

Syzygium sayeri CranePlot DSC_0358
Syzygium sayeri with a bluntly toothed leaf margin. This species has light brown bark and gets impressively big.

Some species have wavy leaf margins, such as S. unipunctatum and S. claviflorum.

Syzygium unipunctatum DSC_0299 (5)
Syzygium unipunctatum has wavy leaf margins which is rather pronounced when looking at the plant from a distance.

Syzygium claviflorum IMG_7710
Syzygium claviflorum is a rather non-descript species, but the wavy leaf margins and rather closely spaced and almost parallel secondary venation seems to be a fairly good combination of features to help with it’s recognition.

“Leaf whispering” Syzygiums can be immensely fun (sometimes in an exasperating way), and the learning never ends. Enjoy.


Hyland BPM. 1983. A revision of Syzygium and allied genera (Myrtaceae) in Australia. Australian Journal of Botany., Supplementary series; Suppl. no. 9.

Posted in Learning Plants, Lifeform - Trees & Shrubs, Myrtaceae (Myrtle family), Tropical Fruit Trees | Tagged , , , , , , , , , , , , , , , | 1 Comment

Aglaia meridionalis (Meliaceae)

Aglaia meridionalis DSC_0788 (3)

This endemic member of the Mahogany family is known as the Rusty Almond, probably due to the red rusty hairs that cover the leaf undersides, twigs and also the fruits. At the same time, this trait makes it one of the most easily recognizable species of the family in North Queensland.

Aglaia meridionalis Millaa Millaa Falls DSC_0403 (1)
A fruiting specimen. This specimen was only about 3m.

Aglaia meridionalis Millaa Millaa Falls DSC_0433 (3)
The fruit capsules covered with rusty red hairs.

Aglaia meridionalis DSC_0787 (3)
Leaf underside covered with easily rubbed-off rusty red hairs

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Piper umbellata (Piperaceae)

Piper umbellatum DSC_0265 (2)

This native pepper species is one of the easiest to identify among the other native peppers. It is more like a weak shrub rather than a vine, and it has the largest heart-shaped leaves which get up to 30 cm wide. The leaves are bright green and very thin-textured and the plant is usually always growing in environments that are ever-wet.

Piper umbellatum DSC_0260 (6)

Piper umbellatum DSC_0260 (5)

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Pioneers of the rainforest

Anyone interested in tropical plants or plant ecology cannot help but encounter the concept of succession. Species that are characteristic of successional habitats or rainforest habitats recovering from disturbance (cyclone, deforestation, etc) are called pioneer or successional species. These species are often characterised by their shade intolerance, rapid growth and absence from mature rainforests. In reality however, and many successional species will persist long after mature rainforest returns, either in the understorey or as emergent species.

Far North Queensland had its own fair share of literature contributing to the science of successional species, and then later to a related topic – forest restoration. A number of authors (Hopkins et al. 1976; see Goosem & Tucker 2013) have proposed classifications of North Queensland successional species which I will list below (asterisks denote exotoc species) under a broad category of Pioneer and Early successional species. It might be noticed also that many successional species are species that occur on rainforest margins and tall (or giant) eucalypt forests.

Acacia celsa
Acacia cincinnata
Acacia mangium
Acacia melanoxylon
Aleurites moluccanus
Aleurites rockinghamensis
Alphitonia spp.
Alpinia caerulea
Alpinia arctiflora
Alstonia muelleriana
Alstonia scholaris
Archirhodomyrtus beckleri
Breynia stipitata
Bridelia insulana
Bridelia tomentosa
Callicarpa candicans
Callicarpa longifolia
Callicarpa pedunculata
Cananga odorata
Cayratia japonica
Chionanthus ramiflorus
Croton insularis
Croton triacros
Darlingia darlingiana
Dendrocnide cordifolia
Dendrocnide moroides
Dicranopteris linearis
Duboisia myoporoides
Elaeocarpus angustifolius
Embelia australiana
Endiandra discolor
Endospermum myrmecophilum
Eucalyptus grandis
Eupomatia laurina
Euroschinus falcatus
Ficus spp. (particularly F. congesta, F. septica, F. variegata)
Flindersia brayleyana
Gahnia aspera
Gahnia sieberiana
Glochidion harveyanum
Glochidion philippicum
Glochidion sumatranum
Guioa acutifolia
Guioa lasioneura
Homalanthus spp.
*Lantana camara
Litsea leefeana
Lophostemon suaveolens
Macaranga involucrata
Macaranga tanarius
Maclura cochinchinensis
Maesa dependens
Mallotus paniculatus
Mallotus philippensis
Melastoma malabathricum
Melia azedarach
Melicope elleryana
Mischocarpus lachnocarpus
Neolitsea brassii
Neolitsea dealbata
Merremia spp.
Pavetta australiensis
Pipturus argenteus
Polyscias australiana
Polyscias elegans
Polyscias murrayi
*Psidium cattleianum
Quintinia quatrefagesii
Rhodamnia sessiliflora
Rhodomyrtus canescens
Rhodomyrtus effusa
Rhodomyrtus pervagata
Rhodomyrtus sericea
Rhodomyrtus trineura
Rhus taitensis
Rubus alceifolius
Rubus moluccanus
Rubus queenslandicus
Schefflera actinophylla
Senecio bipinnatisectus
Sloanea langii
Solanum sp.
Synoum glandulosum
Tarenna dallachiana
Timonius timon
Trema aspera
Trema cannabina
Trema orientalis
Trema tomentosa
Trichospermum pleiostigma
*Triumfetta rhomboidea
Wikstroemia indica
Wilkiea pubescens


Goosem S, Tucker NJ. 2013. Repairing the Rainforest. 2nd ed. Wet Tropics Management Authority and Biotropica Australia Pty Ltd. Cairns

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