I admire people who can walk through the bush and identify the flora without referring to a field guide. To do this I think you need a good knowledge of what flora should be in the area (that will whittle down the hundreds of choices down to the tens), and then a system for classifying them.
For nearly a decade I have been trying to learn all the plants on our property (with little success). I’ve started with the acacias. Acacias are divided into six groups based on the shape and form of the leaves and flowers. Using the colour of the flowers is not very helpful! Group 1 acacias contain wattles with bipinnate foliage (as opposed to single leafed). I call them feathery-leaved wattles. Where I live there are only three species with this type of leaf – the Cootamundra Wattle (Acacia baileyiana) (an environmental weed in this area, planted by the previous owner), the Silver Wattle (Acacia dealbata) and the Black Wattle (Acacia mearnsii).
The Cootamundra is easy to pick – SMALL bipinnate leaves and that unique light blue-green colour. The Silver and the Black Wattles are a bit trickier to tell apart. The Silver Wattle flowers a bit earlier but how do you pick them when they are both in flower or both not? I’m glad you asked. You will have to look closely at the rhachis – the stem down the centre of the leaf. Distributed along the rhachis are tiny oil glands. In the Silver Wattle the oil glands are situated AT the point where each pair of pinnates is attached to the stem (pictured above). In the Black Wattle, those oil glands are BETWEEN the spot where the individual fronds meet the stem (pictured below, click photo to enlarge). Tricky, eh?
Well, that covers the bipinnate wattles. That only leaves 11 more acacia species and several dozen more trees to come to grips with.