AIM: To produce a pressed collection of local weeds (Use only local weeds so as not to spread weeds from one locale to another).

• A4 paper,
• Plastic bags,
• Gloves,
• Paper towel,
• Scissors,
• Plastic sheet protectors,
• Ring binder,
• Newspaper,
• Flat heavy objects to be used as weights, and
• Weed identification materials or weed expert.

A herbarium is a collection of pressed and dried plants. These are mounted on separate sheets of paper which also record details of where and when each specimen was found.

Herbariums are fun to set up and useful for monitoring plants, including weeds, in a particular area.

Setting up a herbarium for weeds involves:

• The specimen should fit onto an A4 sheet of paper.
• To collect safely, students may require gloves or secateurs to collect some weeds.
• Collect intact specimens with undamaged leaves attached to stems and include roots if possible. Try to collect reproductive parts such as flowers, fruits and nuts.
• Place the collected specimen in a plastic bag along with a note that states what it is (if you know) and where it was found.

Plan to press your weeds soon after collection. Specimens left overnight will start to look very sad.

• Use paper towels to dry damp specimens.
• Trim specimens to reduce their bulk and the chances of ‘mould out’.
• Place weeds between separate sheets of folded newspaper. Include a scrap of paper with some of the plants’ details so you can identify them easily later.
• Place weights on your specimens, making sure that each one has something flat immediately above and below. Old encyclopaedias make good weights.
• Store in a dry, well-aired place and check each week for mould. Change newspapers if the specimens look mouldy.
• Allow four to six weeks for a good press.

• Try a ‘microwave’ press. Place plants between two flat plates and zap. You will need to experiment with times and settings.

Microwaved plants tend to hold their colour better.

• You can also experiment with a flatbed scanner to capture the weed as a ‘computer image’. This can produce beautiful images.

After four to six weeks remove the weeds from the newspaper and:

• Tape each weed to separate A4 sheets of paper or card.
• Make a specimen card (see below for a sample) to record information for each weed. Stick it to the A4 sheet.
• Slip the A4 sheet into a plastic sheet protector and clip into a ring folder.

• Common name
• Scientific name
• Where it was found
• How the weed may have got there
• Date
• Collector’s name