Dig up the plants you are going to preserve. Carefully take the entire plant, roots and all. Shake off any excess dirt and debris.
Cut a section around 10 inches long, if you are taking a specimen from a tree branch or large shrub. Be certain to include any flowers or seed pods.
Write down the exact location where you found the plant, and the date. Jot down a brief description of the plant, noting any special features such as flowers or seed pods. You will also need to look up the botanical name of the plant, and any common names. This information will all be written on a label placed with the mounted specimen.
Prepare your specimen for drying by laying it on half a sheet of newspaper. Arrange the plant so that important features, such as flowers and leaves, will be clearly displayed once dried.
Cover the plant with the other half of the newspaper. Place the newspaper-wrapped specimen between two pieces of 12-by-18 inch cardboard. If you have more than one plant, wrap the next in newspaper, and stack your specimens with cardboard between each, and a final layer of cardboard on top.
Press the wrapped and stacked plants in an herbarium press. If you do not have one, you can make one with two 12-by-18 inch wooden boards held together with straps, or even by placing a heavy book or bricks on top of the cardboard over the plant specimens.
Place the herbarium press in a warm, dry place. Examine the plants daily to be sure they are drying in the right position. Make small adjustments, if necessary.
Remove plants from the press when they are stiff and no longer feel cool to the touch. Handle them carefully, as they will shatter easily. Place the plants in the freezer for 3 to 4 days to kill any insects that might be hiding on them.
Lay the plant on 12-by-18 inch acid-free display paper. Arrange the plant to your liking. Trim carefully, if necessary, to make the plant fit the page.
Glue the specimen to the page using a thin layer of white glue, or craft glue. Lift the plant gently to apply glue underneath, then press it down to allow the glue to set.
Apply a label to the bottom right-hand corner of the page, with your identifying information for the specimen. Glue in place.
Cover the glued specimen with a sheet of waxed paper. Place cardboard on top of that, and a heavy rock or book to top off the stack. Leave overnight.
Display the finished page in a frame, or staple pages together to create an encyclopedia of dried plants.