Class materials

Several years ago I studied with the Maine Master Naturalist Program. One of the assignments was to press and laminate a number of specimens - tree leaves, wildflowers, and ferns. I could see their value as a durable teaching tool. Over time I've perfected my technique and experimented with materials. Initially, specimens were layered between clear vinyl and clear contact paper, but the latter wasn't as clear as I might have liked and the former wasn't as stiff as I wanted.



These days, I use transparency film which is super clear and fairly stiff over clear self-adhesive laminating sheets. They're more expensive than contact paper and vinyl, but they're durable and clear which, to me, is worth the investment. You might try hot-laminating but I wonder if the dry-pressed leaves might crack as they go through the machine - maybe not, you could try it. The cold-laminating process is only a bit tricky with one goal - no wrinkles or bubbles. Of course, the other component of a laminated specimen is the specimen itself. For my tree class, I want representative shapes but also a good size for the collection. Sometimes that means selecting smaller-than-average leaves, especially if I'm also trying to get them in their opposite or alternate arrangement. Here's the step-by-step method I've developed over the years and mostly follow these days.

1. Locate the tree species of interest. Sometimes this means planning a field trip (hurrah! field trip!). For example, Chestnut oak's range is southern Maine and Balsam Poplar communities are mapped in the northern half of the State. 
2. Size matters to me. If possible, I collect samples that fit onto a 4" by 5.5" piece of film. This size fits into 4" x 6" photo pages which then go into a 3-ring binder. No worries if the leaves are bigger than that, I just put the laminates into a full-size sheet protector.
3. From the size parameter, I select a dozen healthy leaves of representative shape. Every tree has some that have an odd lobe or insect damage, and some species like red oak have sun-leaves and shade-leaves. If I'm collecting from afar, I might gather a few extras just in case I mess up (gasp!) with the laminating or maybe a leaf gets folded in the pressing book (it happens even when you're super careful).
4. Press these leaves into a field guide or handy book. If they easily fit into a field guide there's a good chance they'll meet my ideal size - and many field guides have a ruler inside the cover so that's helpful. Let the leaves dry for a week or so. If they're particularly moist at collection, I might check on them after a couple of days and transfer them to a dry book as needed. Damp leaves may darken or mold, and that's no good. You can also use a plant press though I find they're a bit bulky for the field. I have a plant press at home, but it's an extra step in a hectic schedule. That said, a plant press produces a really flat leaf.
5. You're ready to laminate! Cut the transparency film based on the size of your specimen. I usually go ahead and cut a dozen pieces so I'm ready for mass-lamination. Set them aside, out of your laminating area so they don't inadvertently get stuck up where they shouldn't.
6. Because they're super clear, lay out the laminating sheet where you've got enough light to see the edges. Begin in one corner and place your specimen, leaving a margin for the transparency film to stick. Carefully lay the cut piece of film over the specimen (bend the film just a little so you can lay the middle first, then ease the sides down to minimize bubbles or wrinkles) to capture the margin you left around the leaf. With your fingers, press from the center out, then press around your leaf - you want a good seal. Repeat this until the laminating sheet is full. You can get four 4" x 5.5" specimens onto one laminating sheet or two that are 5.5" x 8.5". 
7. If you want, add a label with a Sharpie. I use a numerical code so that I know what I've got but students have to focus on what they see. A wise naturalist once told me that once a student names something, they are likely to move on. I want my students to really look at these specimens, describe what they see, and to compare it to another specimen. Then give it a name.

So what do we have laid out here, "T005"? Do you see the bulge at the base of the leaf stem which isn't present at the base of the leaflets? This makes it a compound leaf - the entire thing is the leaf. The bulging at the base of the stem is where the bud develops. At the end of the summer, the leaf (that whole thing with three leaflets) will fall off and leave the bud exposed on the twig. In the spring, the bud will open up and produce a new leaf. The other interesting feature about these leaflets, if you look closely you can see it, is a little protuberance on one side of some leaflets. Almost like the hint of a thumb on waving hands. This tree is often planted in neighborhoods because it grows fast. A friendly tree - neighborhoods, waving hands - what is it? Boxelder, Acer negundo! In the same genus as maples. The "waving hands in the neighborhood" story helps me remember the tree.