Cooler temps key to fall color display

The leaves of a tree turn yellow on a tree in downtown Coeur d’Alene.

The fiery red and orange leaves of a maple tree reach toward a hazy fall sky in Coeur d’Alene.

by JAMIE SEDLMAYER/Staff Writer
| September 23, 2015 9:00 PM

The fiery red and orange leaves of a maple tree reach toward a hazy fall sky in Coeur dAlene.

COEUR d’ALENE — The autumnal equinox arrived around 1:30 a.m., ushering in fall and cooler temperatures.

In Latin, the word “equinox” means “equal night” – “equi” meaning “equal” and “nox” meaning “night.” This signifies the equal parts of daylight and darkness, and the hours of daylight become greatly decreased until the winter solstice Dec. 21.

The brisk air and leaves changing color are what most people associate with fall. So, you may ask, 'What will become of our usual colorful foliage following a summer of smoke-filled skies and the sun shining and temps staying in the warmer zone this month?'

Katie Kosanke, the urban forestry coordinator for the City of Coeur d’Alene said we may see the colorful leaves on trees last longer this year. She said with the steady warmer temps with cooler nights, we can expect the color to change slowly and last possibly through October.

Kosanke said the smoke will not cause an issue with the trees that change colors. She said the sunlight needed for photosynthesis penetrates smoke and reaches the trees anyway.

She said if we have several nights of near-freezing temperatures the trees could all turn and drop leaves quickly though.

“The colors are always there in the leaves,” Kosanke said. “The chlorophyll just hides the red and yellow colors with the green it causes.”

Chlorophyll, a biomolecule and pigment critical for photosynthesis, is created in trees and foliage as a reaction to sun and warmth. With shorter days of sunshine and colder climates dominating the weather, trees stop producing the chlorophyll that keeps their leaves green. The trees slowly make their descent into a dormant state for the winter months, Kosanke said.

“The stressed trees might be the ones people see turning a little sooner,” Kosanke said. “I observe them in the middle of summer, already turning because of stress.”

She said disease, higher temperatures and lack of water can be factors for a tree being stressed.

Meteorologist Randy Mann said the lack of moisture coupled with the warmer temperatures could affect the fall display.

“We need the cold weather to kick it in,” Mann said. “Without it, the fall foliage colors may not be that spectacular this year.”

Though the outlook for vibrant colors may not be good, the weather could still cooperate. With some sunny days and a little rain, we will all be able to enjoy nature's autumn palette a little longer this year.

Jamie Sedlmayer can be reached at jsedlmayer@cdapress.com