Identifying plants

Identifying plants presents some of the same challenges faced when trying to identify invertebrates.

Firstly, there are thousands of species of flowering plants. Happily, however, most have been described and named scientifically (quite unlike the situation for invertebrates or for fungi!)

Secondly, as is the case with invertebrates, there is a special vocabulary used to describe plants and their parts. Learning this language goes along with learning plant anatomy – and both are essential skills to develop for botanical study.

And, finally, there is the challenge of individual variation. Depending upon the particular environment and growing conditions, individual plants of the same species can look radically different.

But there is plenty of good news too. 

The basic 'plan' for all flowers is the same. In different families, this basic plan is variously modified but the fundamentals are constant.

There are excellent, comprehensive resources for plant identification down to the species level – both in text form and on-line.

And unlike many animals, plants don't bite and they aren’t camera shy! 

Observations and data

Typically, leaves alone are not enough to identify a species. We always take the opportunity to identify plants when they are flowering or fruiting. In most cases, flowers are needed for a positive identification.

Tall eucalypts pose a special problem in accessing the flower buds, flowers and fruit. Look for fallen branches but be alert to the possibility that these may have come from neighbouring trees of a different species.

If you are relying on photos, take lots! And of different parts of the plant – the whole plant, flowers, buds, leaves and stems – and at different levels of magnification. You can often get a photo of a plant that is adequate for identification purposes even with a mobile phone camera. 

Size matters. When taking photos in the field, if we don't have a ruler on hand we try to include something in the photo to give us a scale. A coin is good, or even a lens cap. But a ruler is best of course.

And size varies. Eucalypts are a good example. Leaf shape, length and width are all important features, yet for most species their leaves will vary significantly in both dimensions. Take measurements of multiple leaves, trying to 'capture' the full range. OK, a ruler really is a must for field work.

When examining or photographing delicate species, take care. Orchids are particularly susceptible to damage. Avoid touching the plant at all .... and check what you're kneeling on, as where there is one there are often more. Many orchids are declared protected species, and for good reason.

Methods and associated resources

With data in hand, you can begin the process of identification. Two strategies are available to you.

The “can I get lucky?” method (otherwise known as the “quick and dirty” method).

For this method, you’ll need an illustrated guide to the plants in your area. The more local the area covered by the guide, the better – simply to reduce the number of candidate species. 

We use an excellent local guide prepared by Betty and Don Wood, Flowers of the South Coast and Ranges of New South Wales. There is a good chance that you’ll be able to find an equivalent field guide for your area. 

The plants in Betty and Don’s books are ordered according to flower colour. So if your flower is red, you simply flick through the pages in the red flower section until you find something that looks like your plant.

We use the same 'flick through' approach with local field guides that are ordered taxonomically. Of course, if we recognise the family, that helps, but even if we don't, the first thing we do is to simply look for a picture that matches our specimen.

Sounds totally dodgy and unscientific, doesn’t it? Perhaps, but it is surprising how often we’ve been able to identify a tricky species with this method. Results are what count here – not how you get them.

Of course, once you have a candidate species, it is important to cross-check with other references and descriptions, such as some of those described below under the 'systematic method'.

The systematic method

This method generally requires a good deal of knowledge of plant structure and the vocabulary for its description. But it is a fun and worthwhile goal in itself to acquire this knowledge.

The most rigorous form of the systematic method is to work through an identification key, starting with the lowest level of classification to which you are confident the plant under study belongs. 

For example, if you know that the plant is some sort of 'pea', start with the family Fabaceae and work down to the genus and species from there.

Warning! – the truly systematic approach is not for the faint-of-heart. It requires a good deal of background botanical knowledge, depending upon the level of classification at which you start and the group you are working on. If you make a mistake at any step in the key – and it will happen from time to time – you end up in a blind alley and need to backtrack. It's all part of the fun.

If, at the outset, you are confident of the family of your candidate plant, an alternative approach is to do a Locality Search. Both PlantNet and VicFlora offer the option of filtering by location. Be aware that such lists are sometimes incomplete - particularly if you choose a small radius in the Plantnet filter – but it’s a good place to start.

You then work through the descriptions and/or images of each species on that locality list to find one that matches your plant. How useful this method will be depends upon how many species you end up with after your locality search – 10 candidates is workable, 50 less so.

Of course, all of this supposes that you are in fact looking at an Australian native plant growing in its 'normal' environment. If you have a garden escapee .... hhmm, a problem.