Autumn Leaves

For years, scientists have worked to understand the changes that happen to trees and shrubs in the autumn. Although I don't know all the details, I do know enough to explain the basics and help you to enjoy more fully Nature's multicolored autumn farewell. Three factors influence autumn leaf color - leaf pigments, length of night, and weather, but not quite in the way we think. The timing of color change and leaf fall are primarily regulated by the calendar, that is, the increasing length of night. None of the other environmental influences-temperature, rainfall, food supply, and so on-are as unvarying as the steadily increasing length of night during autumn. As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to paint the landscape with Nature's autumn palette.

A color palette needs pigments, and there are three types that are involved in autumn color.

1. Chlorophyll, which gives leaves their basic green color. It is necessary for photosynthesis, the chemical reaction that enables plants to use sunlight to manufacture sugars for their food. Trees in the temperate zones store these sugars for their winter dormant period.

2. Carotenoids, which produce yellow, orange, and brown colors in such things as corn, carrots, and daffodils, as well as rutabagas, buttercups, and bananas.

3. Anthocyanins, which give color to such familiar things as cranberries, red apples, concord grapes, blueberries, cherries, strawberries, and plums. They are water soluble and appear in the watery liquid of leaf cells.

The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is dwindling. Temperature and moisture are the main influences.

A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out. These conditions - lots of sugar and lots of light - spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson. Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.

The amount of moisture in the soil also affects autumn colors. Like the weather, soil moisture varies greatly from year to year. The countless combinations of these two highly variable factors assure that no two autumns can be exactly alike. A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks. A warm period during fall will also lower the intensity of autumn colors. A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors.

I always remember the childhood, when I walked home from school with head bent downward, searching grass and sidewalk for the finest examples, then carting them home and arranging them between sheets of waxed paper.

The maple leaves were always my favorite, brushing the sky with scarlet and gold, transforming the beautiful landscape.

The leaves are beautiful, they make for great science learning, and they're free! Prevent those lovely leaves from disappearing too quickly with one of the preservation methods.

6 Ways to Preserve Autumn Leaves:

1. Press them: Dry your leaves carefully and press them between the pages of a telephone book. Or, place them between sheets of blank newsprint and weight them down. Your leaves will be flat and dry, but may crumble easily.

2. Dip them: Melt some beeswax in a double boiler. Dip each leaf in the wax, giving it a thin, even coat. Allow the wax to solidify before putting the leaf down.

3. Iron them: Place a leaf between two pieces of waxed paper. Put a towel or cloth on top and press with a warm iron. Remove the cloth and cut around the leaf, or try peeling away the waxed paper to see what you get.

4. Plasticize them: Combine one cup glycerin with two cups water and mix well. (You can get glycerin at drug and health food stores.) Pour the mixture into a shallow pan. Place fresh leaves in the pan and lay a sheet of paper on top of them. Put small stones on top to loosely weigh everything down. (I understand some people have had success just putting the tips of leaf stems or even whole branches in the solution, although I haven't tried it.) Leave for about a week; remove and rinse. The leaves won't seem very different, but they'll stay soft and lifelike for a long time.

5. Nuke them: Put 2-3 leaves in the microwave under a paper towel. Microwave for 30 seconds or so. You can also get a special microwaveable desiccant silica gel to place the leaves in first. It better controls the rate and evenness of drying.

6. Laminate them: Run them through a laminating machine. Make sure they're dry first, or the lamination won't stick.

1. Select a leaf. Millions of leaves fall from deciduous trees every autumn, and the selection of vividly-colored leaves can be vast. An ideal leaf for preserving is large and, of course, one you consider beautiful. It should also be somewhat fresh, as the moisture in the leaf will help protect it when it is later sealed. Dry leaves should be avoided as they are likely to crumble while being ironed.

2. Place the selected leaf between two pieces of wax paper. On an ironing board, lay down one piece of wax paper of adequate size to fully cover your leaf. For average sized leaves, a 6-inch by 6-inch square should work. Scrap bookers may prefer an 8.5-by-11 inch sheet of wax paper for scrap booking consistency. Place the leaf on the center of the wax paper and cover with the other--and identically sized--sheet of wax paper.

3. Cover the wax paper with a towel. If your towel is folded, unfold it and place it gently over the wax paper. Take care not to dislodge the leaf from between the sheets of wax paper.

4. Warm up the iron. Plug the iron into the electrical outlet and turn it to the highest heat setting. Allow the iron to sufficiently warm up before use.

5. Iron the towel. When the iron is fully heated, iron the towel for up to 1 minute while applying firm pressure. Ensure the iron passes over all sections of the leaf. The heat from the iron will seal the two sheets of wax paper together, safely sealing the leaf inside. A sealed leaf may be retained for an indefinite amount of time.

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Winter is a certainty that all vegetation in the temperate zones must face each year. Perennial plants, including trees, must have some sort of protection to survive freezing temperatures and other harsh wintertime influences. Stems, twigs, and buds are equipped to survive extreme cold so that they can reawaken when spring heralds the start of another growing season. Tender leaf tissues, however, would freeze in winter, so plants must either toughen up and protect their leaves or dispose of them.

The evergreens-pines, spruces, cedars, firs, and so on-are able to survive winter because they have toughened up. Their needle-like or scale-like foliage is covered with a heavy wax coating and the fluid inside their cells contains substances that resist freezing. Thus the foliage of evergreens can safely withstand all but the severest winter conditions, such as those in the Arctic. Evergreen needles survive for some years but eventually fall because of old age.

The leaves of broadleaved plants, on the other hand, are tender and vulnerable to damage. These leaves are typically broad and thin and are not protected by any thick coverings. The fluid in cells of these leaves is usually a thin, watery sap that freezes readily. This means that the cells could not survive winter where temperatures fall below freezing. Tissues unable to overwinter must be sealed off and shed to ensure the plant's continued survival. Thus leaf fall precedes each winter in the temperate zones.

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