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Friday, 11 May 2012

Collecting and pressing plants

If you are going to collect plants in a scientific way, you should use a proper plant press. The drawing on the right shows a good design for one of the two identical frames that you need.

(It is, by the way, scanned-in from my well and truly out of print Exploring the Environment. The copyright is mine, and I hereby place this image in the public domain.)

The best material is 19 x 6 mm softwood, held together with small nails (I called them "panel pins" in 1985 when I did this pic, but going on more recent experience, I recommend using 1" flatheads).

The nails need to be long enough to go right through both pieces, but be sure to turn the frame over and knock the points down flat (and think about where the nail points will go when you first drive them through!). The size needs to be about that of a sheet of tabloid newspaper, because you will use a lot of newspapers to dry your specimens.

You need to know something about plants before you start collecting specimens, so do some research or ask. You need to be able to guess which species might be protected, and you need to know if you are allowed to collect or not. (If you are in a botanic gardens or a national park, the answer is "no!").

Your specimen size will depend on the mounting paper the plants will go on. Use secateurs or clippers to make a neat cut. The ideal time to take a specimen is when it has both flowers and seed on it.

Some plants may be too large for the amateur to press in the usual way.  This is a cabbage tree palm.
Unless you are carrying your press with you (not a good idea because it will be large), put each specimen in a separate plastic bag with a slip of paper noting where and when you collected it, the type of plant (herb, shrub, tree, big tree, maybe some measurements), other nearby plants and whether you are in forest, scrub or something else, and if possible, the type of soil.

Noting the soil type might seem odd, but some plant species are very fussy about where they grow, and your records might reveal this. Around Sydney, geologists used to work out where shale is exposed from aerial photographs. If they can see cabbage-tree palms, there is shale rock beneath the tree canopy.

You can also use a GPS to locate the plant if you have one, and maybe take a photo of the plant with a digital camera (ah, the marvellous toys that the younger generation have today.  Sheer looxury, that's what it is!)

When you get home, put the specimen and the finder note inside two sheets of newspaper, stack the specimens on one frame, put the other frame on top and use weights, a rope or a belt to squeeze the two frames together.

You will probably have collected a number of insects and spiders with your plants, so try to store the press somewhere outside that is dry and warm.

You should change the newspaper every day, and don't forget to transfer the finder note over at the same time. The old paper can be put in the recycling, but don't use it for other plants, because it will be damp.

After about a week, once the plant specimens are really dry and flat, you can tape or glue them to sheets of white paper. Use PVA wood glue and apply light pressure for an hour. Glue the finder note to the same sheet and store your specimens in a box. In a proper herbarium, poisonous chemicals like camphor and naphthalene are often used to keep insect pests away: these are not hood around the domestic scene.

Now you need to name your plants. You have several choices to identify plants. You can ask an expert, you can look at a book with photos produced by an expert, or you can use a dichotomous key, a set of questions that you work through until you have only one species left. Using a key is hard, but if you are able to ask an expert, you are also able to ask an expert to help you by showing you how to use a key.

In October, my book Curious Minds will be released in Australia.  There you can read about some of the tribulations of early collectors in Australia: the ones who were inadvertently poisoned by Macrozamia seeds (de Vlamingh's party at the Swan River and Banks' party in Queensland among them), and where the type specimens of the early collectors ended up.  You can see two zamias here on the right.

The majority of the type specimens taken by early Europeans are still held at Kew, outside London, but the French collector La Billardière's specimens are now in Florence!

You will also read of Ellis Rowan, an exquisite water-colourist who did wildflowers so accurately that any botanist can spot their genus and species, but who was hopeless at naming plants, and often had to be corrected. She also won lots of awards, much to the annoyance of the mere males who failed to be as recognised, and who engaged in a long-running, vindictive and spiteful war against her.  The usually well-regarded Julian Ashton was one of the most vicious. His motivation seems to have been that she had the temerity to gain a higher award than Julian's brother George.

I'm glad botanists aren't like that.  Well, not often...


  1. Macrozamia, is that related to the palm that caused long term damage to natives that ground it into flour and ate it? Oliver Sacks wrote a story about them I think.

    1. It was a bit more complicated than that. The story is interesting to me because I am severely colour-blind, though not as badly as the folk he describes in 'The Island of the Colour-blind'. Also, I was working on an Australian government contract on Pohnpei in 1993 (not long before Sacks went there), developing their school science curriculum. It irked me a bit that I came and went without hearing about the island.

      The palms in question are all cycads, and from memory, there are about a dozen genera. I wrote an article some years ago about lytico-bodig, for a now-defunct encyclopaedia, so I can see no harm in repeating it. I will dig it out and post it here.

      You can make fadang (flour) quite safely from cycads, if you treat it properly, and the people of Guam knew that well, but they still got lytico-bodig, because there were guns available after World War II, and they shot and ate more fruit bats (flying foxes) and those could eat the cycads unharmed, but retained the toxins.

    2. Note that I have now done this, under the title 'The fruit bats, the palms and lytico-bodig'.