How to identify Australian Native Tree Species by Leaf Characteristics

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How to identify Australian Native Tree Species by Leaf Characteristics

Introduction: When starting out to identify Australian tree species the saying ' Can't see the trees for the forest' comes to mind. The great diversity of native species makes it a challenge to positively identify native specimens in their natural environment. This is not helped by the often confusing common naming of trees by early settlers, being used to only a limited number of tree species occurring in northern Europe. This explains why for example the definition of an oak tree is used on a whole range of different Australian tree families. It is a process of practice and gaining experience in the field to positively identify native trees in their natural environment. Learning a few basic rules on how to use leaf characteristics and other vegetative features is of great help during the process. Using detailed illustrations and a comprehensive language the identification process of native Australian trees by vegetative features is explained on our web page below.
We hope to raise the awareness to the high conservation value of remaining old growth forests in Australia.

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Distinguishing between a Simple and a Compound Leaf

Distinguishing between a compound and a simple leaf

Being able to distinguish between a simple and a compound leaf plays an important role in identifying any tree species.

1. A Simple leaf is made up of a leaf stalk called a petiole and a leaf blade (lamina). A small bud called an axillary bud is positioned where the petiole (leaf stalk) joins the stem. This axillary bud can develop into a new shoot or a flowering stem. Depending on the season and tree species these axillary buds can be obvious or inconspicuous and the use of a magnifying glass is recommended. A pulvinus is the swelling at base of the petiole below the axillary bud.

2. A Compound leaf is formed by two or more separate leaflets. The main difference is the absence of an axillary bud at the base of the leaflet stalk (petiolule). A compound leaf of the Native Tamarind Diploglottis australis can measure more than 1 m in length and 60 cm in width , with some tree species featuring more than 50 leaflets. The graphic above is showing a compound leaf to the right with 5 leaflets and the only axillary bud appearing at the base of the leaf stalk (petiole).
See Compound Leaf Characteristics Pinnate & Palmate for more information on this page below.

To understand this concept of a simple and a compound leaf; acquire a branch sample from a simple leaf tree species known to you such as the common Creek Sandpaper fig Ficus coronata and compare it to a tree species with compound leaves such as the Foambark Jagera pseudorhus or Native Tamarind Diploglottis australis. It is recommended to collect material from mature specimens. It is beyond the scope of these web pages to explain the difference of a 1-foliolate leaf regarded as a reduced compound leaf with only one leaflet and a simple leaf. Any species with this feature are listed as simple leaves.

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Common Leaf / Leaflet Shapes

Common Leaf Shapes Australian Tree Images

The illustration above displays only the most common leaf shapes which are mentioned in descriptions of tree species on our web pages. Green lines in leaf illustrations above are marking the widest points of the leaf compared to the centre line. Other terms used when describing leaf shapes are: orbicular, rhomboid, deltoid, cordate and more. Many Australian tree species can feature more than one leaf shape on the same tree or even branch and the description may read; leaf shape is elliptic to ovate.
It is recommended when identifying tree species by leaf samples to collect material from mature trees.

Common Leaf / Leaflet Margins

Leaf Margins Australian Tree Images

Shown above are the leaf margins definitions we use on our Australian Tree Images web pages, but the illustration does not show all possible leaf margins (edges). Toothed leaves can feature callus tips or actual spines; can be finely toothed or notched. Other definitions for toothed leaf margins in use are; serrate, serrulate or ciliate. Leaf margins can be deeply lobed as in (Figure 7) or show only a couple of shallow lobes. It is quite common to find different leaf margins on the same tree. For example: leaf margins of the Firewheel tree Stenocarpus sinuatus can differ from lobed to entire (Trees Page 5). It is recommended to collect material from mature specimens when identifying tree species by leaf characteristics.

Common Leaf / Leaflet Apices (Leaf Tips) Shapes

Leaf Apices Tips Common Shapes

Leaf tip (Apex singular / Apices plural) shapes are mentioned in descriptions accompanying Australian tree images. Leaf apices shown in illustration above are the most common shapes and are not a complete selection of possible shapes. Classification applies to both leaf and leaflet apex shape.

1. Rounded or also defined as obtuse. Species often featuring this leaf/leaflet apex are the Doughwood Acronychia octandra and Coogera Ayrtera divaricarta.

2. Notched or the botanical definition is emarginate. Guioa Guioa monostylis and Scented Acronychia Acronychia littoralis are common examples of this leaf apex shape.

3. Acute or gradually tapering into a point. A lot of Australian tree species with simple or compound leaves feature this shape of leaf or leaflet apex, Pink Walnut Endiandra sieberi, Forest Maple Cryptocarya rigida, White Booyong Argyrodendron trifoliolatum to mention a few.

4. Acuminate elongated is a leaf apex tapering to a point in a more abrupt way than acute. This shape is commonly found in the genus of Syzygiums like the Brush Cherry Syzygium australis and Weeping Lilly Pilly Syzygium floribundum.

5. Acuminate short differs from elongated acuminate in that it tapers into a point over a shorter distance. Examples are; Red-barked Sassafras Cinnamomum virens and Maiden's Blush Sloanea australis.

6. Mucronate is basically a more rounded leaf apex with a short sharp point. Grey Possumwood Quintinia verdonii and the Native Olive Olea paniculata feature this type of leaf apex shape.

Points can either be blunt or sharp. If the point is a spine of a very fine bristle the apex shape is called aristate.

Common Leaf / Leaflet Base Shapes

Leaf Base Shape Illustration

The ability to recognise common leaf base shapes is useful in identification of native Australian tree species and descriptions on our tree web pages use definitions explained below. Classifications apply to both leaf and leaflet base shape alike.

1. Attenuate: The term attenuate is used for a leaf base shape tapering (narrowing) very gradually into the petiole over a long distance. Examples for this base shape include the Macleay Laurel Aneopterus macleayianus (Page 7) and the Thin-leaved Coondoo Pouteria chartacea (Page 11).

2. Cuneate: The botanical term of cuneate is best described as a wedge shape with the narrow part at the base tapering into the petiole over a shorter distance. This shape is very common with numerous Australian tree species sharing this feature.

3. Obtuse: An obtuse leaf base shape is rounded and approaches the semi-circular. The Brush Ironbark Bridelia exaltata (Page 2), the Creek Sandpaper Fig Ficus coronata (Page 5) and the Red Kamala Mallotus philippensis (Page 7) are examples for this characteristic.

4. Oblique: Being an asymmetric, irregular or uneven on either side where the leaf blade is joining the petiole. This more uncommon leaf base shape is a good identification characteristic and the Hairy Rosewood Dysoxyllum rufum (Page 7) and leaflets of the Red Cedar Toona australis (Page 9) share this feature.

5. Cordate
: Heart-shaped and referring mainly to the indented base of the leaf recurving to below the joint of the petiole with the leaf blade. Tree species with this leaf characteristic are the Lace Bark tree Brachychiton discolor amongst other in this genus. Other more extenuated forms of this shape are called auriculate (forming roundish lobes), sagitate (pointed) and truncate (very shallow indentations not reaching below joint of the petiole).

Leaf Arrangements

Identify tree species by leaf characteristics

1. Alternate leaf arrangement on a simple leaf tree species. Sample shown in image 1 is the Black Plum Diospyros australis
2. Opposite leaf arrangement on a simple leaf tree species. Sample is the Native Guava Rhodomrytus psidioides.
3. Whorl leaf arrangement on a simple leaf tree species. Sample shown in photo 3 is the Brush Box Lophostemon conferta.
Leaflets (compound) with a whorl like arrangement are called palmate, see Compound Leaf Characteristics Palmate below.
4. Alternate leaf arrangement on a compound leaf tree species. Sample in illustration 4 is the Rosewood Dysoxylum faserianum
5. Opposite leaf arrangement on a compound leaf tree species. The Five-leaved Bonewood Bosistoa floydii is the example shown in image 5.

Note: Tree species can feature true whorls where leaves continue this arrangement along older branches or pseudo whorls where leaves change to an alternate or opposite arrangement when maturing. Alternate or opposite arrangements of compound leaves on many Australian tree species is varied. We refer to these different leaf arrangements in our descriptions of native Australian trees accompanying our species identification images.

Compound Leaf Characteristics Pinnate

Compound Leaf Characteristics Pinnate Bipinnate Tripinnate

Green circles show position of axillary buds.
Compound leaf characteristics shown in the illustration above are not a complete selection of possible features. The pinnate classification is separated into imparipinnate which posses a single terminal leaflet and paripinnate without a single last leaflet. Illustration 1 shows a paripinnate compound leaf. Some tree species such as the White Cedar Melia azedarach hold more than fifty leaflets in a single compound leaf. The resource link on our 'Australian Tree Identification' pages shows publications and websites with further information.

1. Pinnate compound leaf. Hairy Rosewood Dysoxyllum rufum and Native Tamarind Diploglottis australis are species with pinnate compound leaves.
2. Bipinnate compound leaf. An example for a bipinnate tree species is the Silky Oak Grevillea robusta.
3. Tripinnate compound leaf. (Not common) The Australian White Cedar Melia azedarach is regarded as a compound leaf with tripinnate features, if sometimes irregular.

Compound Leaf Characteristics Palmate

Identification Compound Leaf Characteristics Palmate

Green circles show position of axillary buds.
4.Compound Leaf Palmate bifoliolate. Image 4 is showing a bifoliolate (two leaflets) palmate compound leaf of the Yellow Satinheart Tree Bosistoa transversa
5. Compound Leaf Palmate trifoliolate. The Australian Doughwood tree Acronychia octandra is a species with this palmate trifoliolate (three leaflets) feature.
6. Compound Leaf Palmate. Palmate compound leaves can feature more than 15 seperate leaflets like the Australian Umbrella tree Schefflera actinophylla.
Illustration 6 shows the Black Booyong Argyrodendron actinophyllum with up to 9 seperate leaflets.

Leaf Venation and Domatia

Domatia Leaf Identification

Domatia (plural) domatium (Singular) are small constructions appearing either as swellings, hollows or hairy bristles on leaf surfaces. They can be very obvious or only visible under multiple magnification, their presence or their absence can assist with identification of tree species. There can be a single domatium or numerous ones and they are mostly found in the center vein axis of the leaf's lower surface but can also appear along lateral veins and on the upper surface in some cases.

The illustration to the left is showing:

1. Domatia which appear as hollow indentations on the leaf's lower surface along lateral veins.

2. Domatia showing as swellings on the leaf's upper surface along the center vein.

Position of center vein, lateral veins and net veins in a pinnate arrangement are demonstrated.

Other terms in use for center vein are; midrib and mid vein
Other terms for lateral veins are; secondary veins and cross veins.

The example shown is the Brown Beech Pennantia cunninghamii.

We only mention the presence of domatia on our Australian Tree Images Pages in the case of good visibility.

Leaf/Leaflet Vein Arrangements

Leaf Venation Patterns, Leaf Veins of Australian Trees

Venation patterns on simple and compound leaves can be useful when identifying tree species. Veins can be hardly visible to strongly raised and obvious on both leaf surfaces. Veins are categorised into a center or mid vein, lateral or cross veins which divide from the center vein and run to the leaf margin. Small net veins can connect lateral veins, but are not present on all tree species.

1. Elliptical or longitudinal. Veins start in one point at the base and join again at the apex of the leaf with the widest spacing being at the center. An example for this vein arrangement is the Tree-Heath Trochocarpa laurina.
2. Parallel. Veins that are running parallell along the length of a leaf without joining. The Bull Kauri Pine Aghathis microstachya shows this feature in its leaves.
3. Palmate. A palmate vein arrangement branches out at the base of the leaf into five or more main veins. A tree species with palmate leaf venation is the Illawara Flame Tree Brachychiton acerifolius.
4. Pinnate. Veins dissect from the center vein and run to the leaf margin in an alternate or opposite manner. A whole range of tree species show this vein composition including the Forest Maple Cryptocarya rigida (Simple Leaf) and the Five-leaved Bonewood Bosistoa floydii (Compound Leaf).
5. Three Veined. Three prominent veins starting at the base of the leaf and running up to the margin by more than half the length of the leaf. Malletwood Trunk Rhodamnia argentea and the Shining-leaved Stinging Tree Dendrocide photinophyllum are examples.
6. Reticulate. Main lateral veins do not run all the way to the leaf margin, but recurve and join. The Common Acronychia Acronychia oblongifolia shows this venation pattern.
7. Penniveined. Very closely spaced lateral veins (often faint) divide from the center vein to the leaf margins. The Blue Gum Eucalyptus saligna is a sample for this feature.

Stipules as Identification Features

Leaf Characteristics Stipules

Stipules in general are apendages emerging in most cases at the base of the petiole (leaf stalk). They can appear in a range of different forms; as a pair of rolled up sheaves (encasing the developing leaf and being discarded as the leaf unfurls), as tendrils (without being discarded), as small leaves and also as spines. They can be easily noticeable to minute in size. The presence or absence of stipules, their different appearances and scaring of young branches can greatly assist in identification of native Australian tree species.

1. Stipules on a Moreton Bay Fig can be up to 15 cm in length leaving a slanting scar on the branchlet. (Alternate leaf arrangement)
2. Stipules removed to show unfurling leaf.
3. Stipules on a Small-leaved Fig at 3 cm in size, other tree species can feature stipules at only a few mm in length.
4. Horizontal stipule scars left behind on the Native Guava Rhodomyrtus psidioides with an opposite leaf arrangement.
5. The Crabapple Schizomeria ovata showing a stipule scar, which is an important identification characteristic for this tree species as its leaf margins and leaf shape are very varied.