HOW TO CREATE A HERBARIUM

Coordinator - AuthorOIKONOMOUDIS IOANNIS

What is a Herbarium?

A herbarium (plural: herbaria) is a collection of preserved plant specimens.

Quality herbarium specimens are an important recourse and require both skill and dedication to produce.

There are four main aspects to making good herbarium specimens:

1. collecting2. pressing & preserving3. mounting4. labelling

When collecting plants for herbarium or voucher specimens there are two basic points to remember:1.Include all available parts of the plant (i.e. all reproductive structures such as fruits, flowers and buds, as well as bark, leaves, juvenile or coppice foliage, etc.)2.Include detailed notes about the plant and it's surroundings.3.Collect two samples of the plant, one for dissection and identification, and another for the herbarium specimen.

In general aim to collect:1.At least the terminal parts of the aerial shoots including leaves and reproductive parts (leaves, flowers, buds and fruits).2.A representative sample (do not simply choose the biggest or prettiest).3.More than one specimen from a single plant if the plant is variable (e.g. juvenile leaves at the base, adult leaves higher up). These will be given the same collecting number.4.One specimen from different plants, if you are trying to show variation within a population. Specimens collected from different plants will have to be numbered separately.5.Collect at least a couple of specimens of each plant. Put one specimen in a plastic bag and keep it in the fridge for identification, and press the other.

Numbering and tagging

• As a general rule, the same number is given to parts collected from a single plant on the same day.

• If small herbs or grasses are being collected, such that several entire plants can fit onto a single sheet of mounting card, these specimens may be given the same collecting number if obtained from the same population.

Specimen Preservation in the Field1. Mesophytic plants and those with delicate petals wilt and

shrivel quickly once picked, resulting in poor quality herbarium specimens. To avoid this you should take your plant press into the field and immediately press specimens as you collect them.

2. As this is not always practical or possible, labelling specimens with tags then storing them in sealed plastic bags out of the sun, is ok on cool days.

3. To maintain specimen quality especially on hot days maintain humidity inside plastic bags by swirling a small amount of water inside the bag first, Dampen some folded hand towel and place this in the bag with the plants, put the specimen filled plastic bags straight into an iced cooler.

The Preserving Process• Herbarium specimens are generally preserved by

pressing until dry. Pressing means to apply enough pressure to hold the plant in a position that best displays the botanical features while drying.

• The keys to achieving well pressed plants are:1. Dry them as quickly as possible in a good plant

press.2.Care for the specimens as they dry.

Plant PressPlant presses come in various forms but usually consist of two wooden boards or lattices (30 x 45 cm), cardboard and newspaper arranged like a sandwich (pictured beside). Straps or belts are wrapped around the press to hold it together.

The two parts of the press

• Open a sheet of newspaper, place your plant on one side and fold over the top of the specimen. Newspaper or large sheets of blotting paper are used as they absorb moisture from the specimens.

• On top and below this plant/newspaper sandwich place a sheet of cardboard. Corrugated cardboard is better than solid cardboard as it allows the air to circulate within the press, helping the specimens to dry quickly.

• Cardboard is also important within the press as it provides flat surfaces to dry the specimens against.

• To complete the plant press, stack several plant/newspaper/cardboard sandwiches together and place a wooden boards or lattices on the top and bottom (pictured above). Lattice is also preferred as it helps the specimens to dry faster.

Preparation of the plant specimen for pressing

• Around the stack, wrap rope, leather belts or nylon straps and tie or fasten to hold the press together and apply pressure.

• If you do not have a plant press, pressure may be applied by piling telephone or heavy textbooks on top. Either way, the pressure should be even across the specimen so they dry flat. Specimens with bulky parts (e.g. eucalyptus fruits) may require thick folds of newspaper around bulky fruits or branches so that pressure is transferred to the less-bulky leaves and flowers.

• Remember, the aim is not to squash the water out of the specimens, just to hold them flat in position while they dry.

Simplified diagram of a plant press.

Care while drying• Use a lattice press.• Use cardboard with internal corrugations.• Use blotting paper to absorb the moisture.• Stand the press in a warm, dry place, e.g. a cabinet-type clothes drier set at low heat. Be careful not to burn the specimens or press.• Replace the newspaper to remove moisture and fungal spores.

Replacing Newspaper and Rearranging Specimens

• Newspaper sheets should be replaced daily to remove moisture and fungal spores.

• After the third day this can be done every 2-3 days until the specimens are dry.

• When changing the newspaper re-position the specimens while they are still pliable.

When rearranging the specimens• Ensure all botanical

features are showing, including both lower and upper leaf surfaces.

• Make sure the specimens will fit on the mounting card when dry, remembering to leave space in the bottom right or left hand corner for the label.

Handling Specimens• Always handle your specimens with care to

prevent them from breaking or parts from falling off.

• Some plants inevitably drop their leaves, seeds or flowers. If this happens, collect these parts and put them into a labelled paper envelope alongside the drying specimens. These will be added to the herbarium specimen at the mounting stage.

Mounting• To mount a specimen means to adhere it onto a

sheet of herbarium card. A well mounted specimen should display both artistic and botanical qualities.

• It should be arranged on the card in a balanced, aesthetically pleasing way, paying attention to:

• Orientation and type of mounting card.• Arranging and attaching the specimen.• Position of label and accompanying annotations.• Keeping loose parts in specimen bag.

Mounting Card• Official herbarium

specimens are mounted on 29 x 43 cm archival quality (acid free) white mounting card.

• The direction of the card is "portrait" (vertical).

Arranging the Specimen• Leave a 1cm border around the edge to allow space for holding when picking up the card.• Single specimens should be centered on the mounting card and are usually placed vertically or diagonally across the sheet.• Small plants with multiple specimens should be arranged in evenly spaced rows spread over the whole card.• Orientation of the plants should represent their habit, i.e. usually flowers to the top and roots towards the bottom.• Flip the specimens onto the side that displays the most botanical features (i.e. flowers, fruits, both sides of leaves, etc).

Attaching the Specimen• Specimens can be

attached to the mounting card by gluing, sewing or with tape.

• Glued specimens can not be removed to expose the underside and can not be remounted.

Attaching the Label• Place label in the lower right hand corner.• Place 1cm in from the edge of the card to allow space for holding and to prevent damaging the label.• Use archival clear gum glue.• Glued down along the top edge only.• Keep the label free from mounting tape and specimens.

Labelling• At a minimum your label should include:1.Family and scientific name of the specimen,

including the authority.2.Collector's name/s.3.Date of collection.4.Locality where the plant was collected, including

latitude and longitude.

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