Collecting and pressing specimens – step by step guide

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If you want to identify a bramble you will need to press and mount a specimen which you can then send to a bramble expert for determination or take to a herbarium to compare with other specimens. It is also invaluable to build up your own collection of reference specimens, particulary those that have been named in the field by experts. This step by step pictorial guide explains my own recommended methods of collecting, pressing and mounting bramble specimens. (Not yet complete, but will be added to in the coming months.)

Jump to:

1. Collection

2. Description and photography

3. Pressing


1. Collection

More will be said on choosing suitable specimens for collection in due course, but it is better to find well grown material that is in good condition, not damaged and not eaten by caterpillars. Avoid brambles that have grown up after being cut back or are growing in full sun or very heavy shade. One of the biggest pitfalls in collecting brambles is unwittingly collecting stem pieces (see definition below) which do not match the panicles (i.e. belong to different species). Even experts do this frequently and mixed material is frequently enncountered in herbaria. Check that the shape of the leaves lower down the panicle are similar to those on the stem. It can be surprisingly difficult to find stem pieces on some brambles, particulary the suckering species in section Rubus.

Ideally collect three panicles (i.e. inflorescences with 1-2 sets of leaves below) and three stem pieces (a stem piece is a section of stem from the first year growth, technically known as the primocane). These should be about 10-20cm long with two leaves attached. Eventually one panicle and one stem piece will probably be discarded. One of the panicles can be used to remove flowers for closer examination. The aim is to end up with two duplicate herbarium sheets in case one needs to be sent to a referee or deposited at a later date into a public herbarium.

Roll up each specimen loosely in a sheet of newspaper. This will keep them separate and make them easier to handle. The newspaper also absorbs excess moisture and helps collects any fallen petals which can then be examined later. Other collectors tie a luggage label around each bundle, but if this is done specimens will snag on each other in the bag and some pieces may come free.

For transportation in the field use a thick plastic shopping bag, preferably white in colour to prevent over-heating in the sun. Bags inevitably become crumpled and faded over time, and combined with the batologist's attire of torn trousers and dishevelled clothing adds to the tramp-like effect – which beneficially puts a few people off asking what one is doing!

One bag will hold about 7 to 10 specimens, but it is wise to keep a separate bag for each locality visited. Some collectors use a separate bag for each specimen and stuff these into a large rucksack, but it is easier to carry round a single bag. Collecting more than 10 specimens in a day is not recommended, as one will not have enough time to look at them the next day.

Specimens should be coded for future reference or given a brief description or alias name (e.g. based on an unusual feature of the plant or simply a note of its petal colour and series, e.g. pink-flowered Micantes. Write the date, location and details of habit and habitat in your notebook. Record at least an 8-figure or 10-figure grid reference using GPS. You may want to return to an individual bush if you think it might be something interesting, so if necessary record exact details of where it was.

Mark the reference code on the corner of the newspaper.


2. Description and photography

Keep your bags of specimens in the refridgerator overnight. After a day's collecting it is usually best to examine your specimens the following morning in good daylight.

Use a suitable old table underneath a sunny window to inspect, photograph and press your specimens. You will need some A5 scrap paper to make notes, a ruler, clear sticky tape, sticky notes, a hand lens and your secateurs. For flimsies use good quality artists' A2 cartridge paper folded to A3 size. The paper is about 150gsm so stays rigid enough to be able to handle and move specimens without them bending too much.

Unwrap your specimen and separate the pieces.

If you didn't take photographs in the field (or even if you did) it is very useful to take some of the specimen before it is pressed. It is best to use a camera with flash to give good detail, reduce shadows and avoid colour casts. By photographing on the white flimsy it is easier to correct any colour casts (most photo editing packages will have an automated method of doing this).

In particular, take photos to show petal shape, size and colour (collect any that have fallen off). The petals of this specimen were virtually hairless around the margins – quite an unusual feature. It is useful to photograph against a ruler, for scale.

If you want to preserve the shape and size of the petals use tweezers to place carefully on the underside of some clear sticky tape, then stick the tape onto some paper.

Take some photos to show the panicle and form and colour of the flowers. Note that the panicle of this specimen is still fairly young, as most of the flowers have not yet opened, so is not really ideal for permanent mounting.

It is important to take some photos of the flowers side-on to show the relative length of the stamens and styles. This specimen has relatively short stamens, either less than or just about equal to the styles – a relatively uncommon feature.

Photos of leaves are useful to show their colour and texture, which will change when pressed. It is less important to photograph the stems (close-ups would be needed to show the hairs and glands, if present). Note that although pairs of leaves were collected in the field, these have been cut into individual 1-leaf pieces each with a piece of stem up to about 5-10cm long (sometimes it is better to cut up individually in the field in any case). Eventually one of these will be mounted the right way up and one turned over to show the undersides. If short of material then twist one of the middle leaflets around.

I have found that thicker stems are best cut down the middle with a mounted razor blade or large scalpel, then opened out. This helpfully reduces their thickness when eventually mounted, but the cut pieces often become separated and the piece without the leaf attached may go astray.

Take off a flower or two and dissect under a binocular microscope to check carpel colour and to see whether the carpels and receptacle are hairy. If the receptacle is hairy, the hairs may protrude between the carpels or form a fringe of hairs at the base of the carpels. A good hans lens will also suffice for this. Also check several flowers to see if there are any hairs on the anthers. On a single panicle there may be a mixture of some flowers with hairy anthers and some without, or some with only one hair on one anther and some with a few hairs.

Write your notes on a piece of A5 paper (or any scrap paper). Include details of the locality (including grid reference and vice-county, not shown here). Note any features that cannot be easily determined when the specimen is pressed and dried, such as flower diameter, colour and size of petals, colour of styles, etc. Most of this information will be transferred neatly onto a herbarium label in due course. You may also wish to make notes on diagnosis, e.g. steps taken whilst following the keys in Edees & Newton. Here, I thought the bramble was possibly Rubus micans, remembering that this species has short stamens and weak prickles (it did key out to R. micans but the leaf shape is clearly wrong for this species).

At this stage you should discard any very poor material, such as torn leaves or poorly developed panicles, and press the remainder. Later on you will choose the best looking pieces for mounting. Only then will unwanted pieces be thrown away, although even these are usually worth retaining loose in newspaper. Note that some bramble collectors only mount specimens that are to be deposited in herbaria and keep all reference material loose for ease of examination.


3. Pressing

For pressing you will need a stack of newspapers of the smaller size used by most national and local newspapers and various sized pieces of corrugated cardboard (see photos below), including some cut as herbarium boards (i.e. a little larger than A3). Take two sheets of newspaper at a time, folded and arranged so that one overlaps the other by about 8cm. Thus one double sheet will fully cover the A3 flimsy. You will need a stack of these made from 10-20 newspapers, depending on how many specimens you intend to press.

Start by arranging 2 or 3 leaves of the specimen on one of the opened out (double) sheets of newspaper. Keep the stems to the left hand side and fold over the newspaper.

Place another couple of papers (i.e. newspaper sheets) on top, then do the same with some more stem pieces, this time arranged to the right.

Place some cardboard between to pad out the space between the stems. Then add some more papers.

Note: the stems do not really need to be folded within the newspaper sheets – I was out of practice when I pressed this specimen and forgot what I usually do! It does help keep the pieces together, but it is too easy to accidentally remove a sheet of newspaper for drying without realising that there is something inside it. For stem pieces with thicker stems it is recommended to arrange them so that the stem lies beyond the edge of the flimsy and the boards, i.e. parallel to the edge of the stack. Using this method 4-6 leaves can be arranged in one layer without overlapping and without the need for padding. The only problem with doing this is that the stems will twist, but with practice this can be corrected during the drying process. I will add some photos to demonstrate this at a later date.

Next do the panicles. Arrange between papers in the same way as the leaves (no need to put inside folded paper). Pad as necessary with cardboard. Bear in mind that this is just a rough pressing which simply acts to wilt the material enough so that it can be arranged more carefully later. It is not important at this stage to get completely even padding between the pieces. Some large and complex panicles will take several days to completely flatten out.

Add more papers, then do the next panicle.

As the stack gets bigger it is important to keep it padded top and bottom.

Finally add the specimen notes and mounted petals, and add more padding if necessary.

Close over the flimsy and add a label bottom right with a sticky note with date, location and reference code.

Add boards top and bottom.

Transfer to a plant press (the sort with straps) or alternatively weigh down with a suitable heavy object! I always use books. At this initial pressing stage it only necessary to use relatively light weight – enough to flatten the specimen but not so much as to cause any folded leaves to be come creased.

Change the papers (i.e. the newspapers) after 12 hours or the next day, i.e. remove all the papers and boards and spread out to dry in a warm place.

Start with a fresh board and a few papers. Stack the leaves/stems and panicles between papers, as before but use 2-3 double-sheets between each piece to absorb moisture. Pad as evenly as possible.

A panicle when first removed from initial pressing looks like this:

Open out the leaves and turn one leaflet over to reveal the underside. Arrange smaller leaves in the panicle so that peduncles and flowers lie on top of them (for complex panicles this may need to be done in stages for the first few times that the papers are changed).

Add padding, labels, more papers and close the flimsy

Add board on top and the stack is ready for the next specimen!

Weigh down with books as before or if using a plant press transfer to a warm, aerated place. Stack A4 size books in two piles using heavier weight than before. Softback books are sometimes useful because they bend to the curve of the top board.

Change the papers every day for at least three days and thereafter every 2-3 days. After 2-3 weeks the specimens should be dry, but it is best to keep them between sheets of newspaper with a little padding, so they can be stacked until they can be mounted.