Pressing Flowers - The History & The Science
Pressing plant materials is a method for capturing and preserving flowers and plant material which has been used for centuries as a way to preserve the plant specimens.
Early botanists like Joseph Banks who was part of James Cook’s first voyage on HMS Endeavour, used the pressing techniques we still use today to bring back the samples they collected on their scientific expeditions so they could study them and share their discoveries. A collection of these pressed plant specimens is known as a herbarium. Today the worlds herbaria are linked in a global network which shares the data from samples collected for hundreds of years for use by a huge range of research fields from botany to climate science to engineering.
For many of us, this important scientific methodology can be used as a way to capture the beauty of nature, freezing a moment in time during the life cycle of a flower or plant, and a snapshot of a particular season.
Water inside the cells of plants gives them much of their structure, shape and strength (or turgidity to get scientific!) Flower pressing works by providing scaffolding to a plant so it can maintain its structure as it loses the water from within its cells. Not all plants and flowers press successfully and some dry more quickly and change less during the process than others. The trick is to find joy in experimenting!
Picking Flowers for Pressing
The best time to pick is when the plants are at their driest – in the middle of a dry day when they aren’t wet with dew or rain. This gives you a head start on the drying process.
Pick wildflowers sparingly, leaving plenty for pollinators and for others to enjoy. Ask permission to pick on private land.
In general, picking leaves, flower stems, fruit and seeds for personal, non-commercial use is fine and legal in the UK countryside. However, there are a few exceptions to this, including certain protected species and plants in conservation areas or sites of special scientific interest so it’s always a good idea to know what you’re picking and whether you are walking in one of these protected areas.
It is also illegal in the UK to uproot or dig up a plant from where it is growing without permission from the landowner, so always cut or pick rather than pulling or digging up, unless you have permission.
Be careful of thorns. Be aware that some plant material is poisonous and some can cause skin irritation. Only pick species you know are safe.
How to Press Flowers with a Flower Press
Place your flower press on a flat, sturdy surface, with the bolts all in place, protruding upwards through the six holes in the wooden base board.
Lay one piece of cardboard on top of the base board and place a piece of blotting paper on top of that.
The cardboard provides structure and keeps each layer in the press flat. The blotting paper draws and absorbs the moisture that comes out of the flowers.
Carefully place flowers, foliage, grasses, petals and other plant material you wish to press onto the blotting paper. Carefully manipulate the plant materials into the shape and composition you want each to be. Once pressed, they will be fixed in this shape. This may mean gently pushing the flower heads face down so the petals splay outwards and the flower is captured in an open composition. If the stem sticks out at a right-angle from the flower head, it can help to trim off as much of the stalk as you can without causing the flower to disintegrate.
You can place multiple plant materials on to each sheet of blotting paper. However, try not to overfill the page. Make sure each of the plant materials has its own space so the blotting paper can absorb its moisture effectively, and ensure the plant materials don’t overlap so they don’t get stuck together.
Your pressings will be more successful if you arrange plant materials of similar thickness on the same layer so that an even pressure is exerted onto each of them.
Once you have arranged your plant materials on the blotting paper, lay a second piece of blotting paper on top and smooth down with your hands to press the flowers down in the position you have arranged. You can carefully lift the blotting paper to check and reposition if you need. Then place a sheet of cardboard on top.
You can continue to build multiple layers like this within your press. Each layer consisting of cardboard, blotting paper, plant materials, blotting paper, cardboard. As shown in the image below.
Next, place the wooden top board on top, threading the bolts through the holes in the wood. Thread the washers onto the bolts so they sit on top of the wooden base board and then screw the wing nuts down evenly.
The wing nuts should feel tight but take care to not over-tighten the wing nuts because this may cause the wooden board to bend and, as a result, the board will not exert even pressure onto your flowers.
Leave the press in a warm, dry, well-ventilated place to allow your flowers to dry. This can take as little as a week or up to six weeks or more, depending on the types of plant material and how much moisture they held to begin with.
Check the press occasionally and turn the bolts if needed to maintain pressure as the plant materials dry out and flatten. Also check the blotting paper to make sure it isn’t saturated. If the flowers and paper feel wet, you can gently reposition the flower to a dry patch of paper or replace the paper if it is very damp.
Opening your Flower Press
When you open up your press to check or remove your pressings, the dry pressings will be very fragile so be slow and gentle when peeling back the blotting paper to reveal the flowers.
A Note on Preserving Colour
You may notice that some of your flower pressings lose their colour as they dry, which can be disappointing. According to botanist Professor Stephen Harris, curator of the Oxford University herbaria, “Three things appear to determine how well dried plants retain their colours when pressed: type of pigment and mechanism of pigmentation; the chemistry of individual plant cells; and the speed of drying.”
“Fat-soluble carotenoid pigments, which give some flowers their orange and yellow colours, may be remarkable stable when dried, for example, the specimen of Leonotis leonurus (pictured below) was collected and dried in the late-17th century. However, most plant pigments are water-soluble anthocyanins which are often readily lost when cell membranes break during drying.”
As the cells of some plants are damaged during the pressing process, the chemical balance can be disrupted or protective chemicals which also happen to break down colour may be released. Both of these factors can be the cause of colour loss in your pressings.
These physical properties of some plants cannot be helped and explain why some flowers seem far more likely to lose colour no matter what you do.
So that leaves the one thing you can have some influence over – the speed of drying.
Professor Stephen Harris again: “With herbarium specimens, speed of drying appears to be important for retention of colour in the short term – most dried plants are going to lose colour over decades. Speed seems to be important because fewer cells are broken (and hence less of the chemicals that may interact to change colour are released) and also fermentation of plant material does not start.”
“Historically, there have been numerous methods tried to preserve colour in dried flowers – most of which are both highly toxic and impractical. The best way that has been found is to dry quickly.”
In order to help your pressings dry quickly, and therefore help them retain as much of their colour as possible, you can place your flower press in a warm spot while your flowers dry.
Learn More About Pressing and Drying Flowers
If the science and history behind pressing flowers piques your interest as much as it does mine, you might enjoy watching my conversation with botanist Professor Stephen Harris, where he explains more about the biology of what happens to plants as they dry and are pressed.
We also talk about how long dried and pressed flowers last, why some flowers dry better than others, the history of plant pressing for scientific use and how flower pressings collected hundreds of years ago can help current research into a huge range of subjects including climate change and engineering.
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