Suggestions for collecting and Preserving Leaves - Seeds - Woods for your study kit are given, below.
References: "Introductory Forestry" (4-H 641) pg 7, 11 and "General Forestry" (4-H 642) pg 3
Collecting - The best time to collect leaves is early to mid-summer when they are full grown, but not yet full of insect holes, spots, and bumps. Collect the terminal twigs with at least two leaves, preferably more, from mature trees in full sunlight. Look the tree over and collect typical leaves for that species. Collect at least two specimens of each species and mount the best specimen. Specimens collected in midsummer are easier to press than those collected earlier (but may have more damage).
Pressing - Place the leaves between two layers of newspaper with cardboard or a blotter on the outside of each paper. Put a heavy weight such as a brick or heavy book on top of your homemade leaf press. Be sure to change the newspapers every day or two for at least two weeks because they absorb moisture from the leaves. If you don't change the newspapers your leaves may turn dark or spoil. One way to hasten the drying is to place your leaf press in front of a fan or air conditioner. Another method used to press leaves is to place the leaves between two layers of waxed paper and then press them with a hot iron. Sometimes this makes the leaves smoother and helps them keep their color.
Mounting - Fasten your leaves to paper with clear rubber cement or strips of transparent tape. Traditionally we have used herbarium paper (16.5 x 11.5) but many leaves will fit on regular 8.5 x 11 if you choose to make a more compact, storable kit. If you make a smaller kit please be aware that some trees have leaves that are quite large and may not fit well. However, most leaves will fit and then can easily be kept in a notebook. When pressing one leaf of each specimen should be pressed with the underside of the leaf up (so students can see the back). Cover the front of the paper for protection. Note - I have been doing some experiments with lamination and it appears to work very well. We used 3 ml thickness because it bends around the specimens better than thicker laminate. I have not yet tried it on samples with thicker stems (like conifers have) and suspect that these stems might need to be split long-ways to lay them flat. The laminate holds the sample well, gives some stiffness, and should delay deterioration considerably. You may want to affix the sample to a piece of heavy cardboard to keep from bending and breaking the specimens.
Collect several representative seeds from the trees listed. Collect seeds when they are ripe and dry. Continue to dry after collection, for at least a week. Seeds collected in the fall should be stored over winter in a dry place in paper bags or similar containers.
Resources:• Iowa State has an interactive tree ID website that you might find helpful in preparing your team for the contest (www.extension.iastate.edu/pages/tree/)
• VPI has put out great forestry/ecology website for younger 4H’ers, or youth in general (www.ext.vt.edu/resources/4h/virtualforest/)