Why do leaves change color? What colors should we project in light?

FB Omi Why Leaves ChangeOne of the most frequently asked questions about the natural world is what causes the flamboyant change of color in deciduous trees, those trees that lose their broad leaves in the fall.  The answer to that question is chemical and depends upon the initiation of, and ending of, the seasonal production of food for the tree.

All living things require food to continue their existence.  Plants are no different.  Trees manufacture their own food during the warm months of late spring and summer.  The chemical chlorophyll is present in large amounts in the young, newly sprouted leaves, and it continues to be produced and destroyed during the warm summer months.

Trees’ leaves are their nutrient manufacturing sites. Taking water from the ground, the plant’s roots direct that water to the leaves which have absorbed carbon dioxide from the atmosphere.  Chlorophyll is the key element required for the process of photosynthesis, the combining of carbon dioxide, water and sunlight, causing them to change into the sugar glucose.  This glucose is the food which travels from the leaves to the rest of the tree as the plant’s energy and food source. Food is also stored in the tree’s roots during autumn and winter, the time when nutrient production is halted, for use in the following spring.

Not only is chlorophyll the major player in the production of a tree’s food thru its role in photosynthesis, chlorophyll cells are composed of green pigment, and they provide the green color one sees in the leaves during the spring and summer.  But chlorophyll cells require abundant sunlight to exist and, as fall arrives, the days shorten and sunlight lessens.  The green chlorophyll pigment stops being produced and disappears from the leaf.

Due to the abundance of the chlorophyll cells in the leaf throughout the warm seasons, other color pigments, whose cells are also present in the leaf at the same time, are hidden.  Foremost of these additional pigments are the carotenoids and xanthophylls.  People know these pigments best for the colors they produce in fruits and vegetables such as bananas, corn and carrots.  The carotenoids and xanthophylls also gradually change the leaf’s color to the early, beautiful yellows and oranges that signal the beginnings of the leaf color season while the green chlorophyll dissipates entirely.

Allowing the leaves to live longer and continue to produce energy for the plant, other pigments, the anthocyanins, develop after chlorophyll begins to disintegrate. The bright red and purple leaf colors are from these pigments whose cells’ ph determine the variety of reddish hues seen.  Cells that are acidic produce pink to scarlet red colors.  As the acidic content lessens, the hues become a deeper red to purple.

A fourth pigment found in some trees such as oaks are the tannins,  The tannins also develop the golden yellow hues found in trees such as the beech by combining with the carotenoid pigments.  Tannins are also always present in the leaves of the trees which they help color, but they, too, must wait until the  chlorophyll cells have been removed to be noticed.

A number of factors other than chemical influence the hues seen in the fall leaves.  Natural events such as droughts, excessive rainfall, severe heat or killing frosts will limit and dull the beauty of nature’s autumn splendor.  The most successful color presentation will occur after a wet, but warm, spring, a temperate, evenly moist summer and an autumn with cool nights and sun-filled days.  As previously stated, color is determined by the different pigments the leaf contains.  Except for chlorophyll not all pigments are found in every type of tree leaves.  Only those pigments which are originally in, or are created in, the tree leaves during the growing season will determine which part in autumn’s color palette a specific tree will play.

Following is a list of trees and the hues they exhibit during autumn.  You might find this useful when designing lighting for a production that needs projected leaves.  If you know what sort of trees the scenery is based on, then here is a reference as to what colors you should be projecting.

American Beech – golden yellow turning to light orange

American Hornbeam Birch – orange

Aspen – golden yellow

Black Maple – yellow

Black Oak – yellow

Blackjack Oak – red

Black Tupelo – crimson

Bradford Pear – red

Cottonwood – yellow

Dogwood – deep red

Eastern Hop-hornbeam – yellow

Elm drab – brown

Ginkgo – bright yellow

Hickory – golden yellow

Oak – tannish brown

Red Maple – scarlet

Sassafras – red, yellow, orange

Scarlet Oak – scarlet

Silver Maple – yellow-orange

Sourwood – deep red

Southern Red Oak – red

Sugar Maple – red, yellow, orange

Sweet-gum – yellow or red

Tulip Poplar – yellow

White Oak – orange

Winged Sumac – bright red

Yellow Birch – bright yellow

If you want to have some fun with playing with some gobos to project leaves checkout this link…  http://www.stagelightingstore.com/Stage-Lighting-Store/Leaf-Steel-Gobos

If you want to have some fun with some colorful glass to give some multi-colored effects with these gobos check out…

http://www.stagelightingstore.com/Stage-Lighting-Store/Rosco-Colorizers

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