Favorable Weather Reveals Fall’s True Colors

This morning, a misty fog gently moved through the garden muting the vibrant colors of fall. Leaves, heavy with dew, drooped. Those that had completed their life cycles, relinquished their hold on branches and drifted lazily along soft air currents. How still, serene and incredibly gorgeous the garden was on this cool, fall morning.

But it wasn’t long until the sun banished the fog and transformed the still morning into a blaze of vibrant color. Everywhere I looked, there were shades of yellow, orange, red, purple, pink and brown. Some color combinations were even more exquisite against a backdrop of green, gray or blue evergreens.

Near the house is a sweet gum tree. Its leaves, and those of the moonglow maple, are extraordinary and are easily my favorites in the fall lineup. They gradually change from one exciting color or combination of colors to another. Right now the sweet gum is ablaze with yellow, orange, red and burgundy. Behind the sweet gum is a crimson Japanese maple and a vine maple, dressed in a collection of yellow-red-purple leaves. Off to the side is a big blue spruce flanked by the gold and purple leaves of a dogwood, all against the backdrop of our neighbor’s bright yellow birch. The entire garden is a palette of intense color.

Why do leaves change to this wide variety of color? And why are they more colorful some years? The answer lies in the pigmentation of the leaves and the weather.

The main pigment in leaves is chlorophyll - which makes leaves green. Chlorophyll is the primary catalyst in manufacturing the plant’s food.

This manufacturing process is called photosynthesis, a term we all learn about in school. It’s a process by which chlorophyll utilizes the sun’s energy to turn water and carbon dioxide into food for plants. Once the days grow short and the temperatures begin to drop below 45 degrees, the photosynthesis process declines and eventually stops.

The leaves are no longer needed for food and they drop.

But before they drop, the green pigment (chlorophyll), fades and other less dominant pigments begin to show up - carotenoids, tannins and anthocyanins. These are the guys that give us the technicolor show.

Carotenoids are the yellow pigments. They are found in all leaves. Though this pigment is overshadowed by green chlorophyll, it is always present. In fact, it is responsible in part for the manufacture of chlorophyll. Carotenoids attract the sun’s light, turning it into energy for the production of chlorophyll. Once chlorophyll production is shut down, the yellow pigment becomes dominant, as seen in the brilliant yellows of birch trees, certain maples, mulberries, peonies, daylilies and many more.

Tannins are responsible for the brown color also found in all leaves, and eventually all leaves will turn brown. Some leaves have more tannin than others, for example, copper beech and some oaks.

The pigment anthocyanin is the key ingredient to the spectacular reds, purples and pinks in fall leaf color. Unlike carotenoids and tannins, it’s not present in all trees. And for this pigment to produce truly brilliant colors, there must be an abundance of bright sunny days, like we’re experiencing this fall. In fact, without enough sunlight, the leaves may only turn yellow and then brown and drop.

Colors are at their peak when days are sunny and warm and nights are cool - below 45 degrees and above freezing. During these conditions, photosynthesis slows gradually, allowing sugars to build up in the leaves.

The sugars are used to produce the anthocyanins.

Sometimes leaves are killed by hard frost and immediately turn brown before they can begin their color change. Sometimes these frozen leaves remain on the tree all winter. There are certain trees, like the pin oak, that not only have naturally brown leaves, but it’s normal for the tree to hold these leaves all winter.

We escaped without an early hard freeze this fall and leaf color couldn’t be more spectacular. For a megadose of this autumn splendor, the Finch Arboretum is offering its annual fall leaf festival Saturday from 10 a.m. to 2 p.m. This is a perfect opportunity for you to choose the trees you would want for their fall colors.

The WSU Master Gardeners will offer a tour through the street tree collection beginning at 11:30 a.m., and the maple collection at 1 p.m.

There will be demonstrations on correct pruning techniques, worm composting, storing summer bulbs, decorating planters and leaf art.

Find out where the best hiking trails are in our area and romp through piles of leaves. Come rain or shine, this event is always gorgeous and fun.

The following fields overflowed: CREDIT = Phyllis Stephens The Spokesman-Review