“Autumn days come quickly, like the running of a hound on the moor.”

~Irish proverb

October has come with pumpkins filling every available space until Thanksgiving. Yes, autumn comes quickly, sweeping across the land, making changes along its path. There is no possibility of autumn backtracking into summer once leaves begin to fall.

Last week Montana was hit by a blizzard. The Eastern Sierra was dusted by its first snowfall. Here in La Crescenta, the nighttime temperatures are now dropping into the 50-degree range. The change of seasons is often subtle in Southern California and colder weather isn’t always a reliable indicator. Two of the most dependable, especially in La Crescenta, are shorter days and the turning of leaves on local liquidambar trees from green to yellow and, eventually, red.

As the days get shorter every autumn trees across the country produce spectacular displays of fall foliage. The factors that influence autumn leaf color are shorter day lengths and weather (primarily cooler temperatures and less moisture). Brighton – our new golden retriever – can attest to the first. Her walks have become fewer and briefer; her owners don’t enjoy the earlier arrival of dark evenings. Low humidity or less moisture resulting from the Santa Ana Winds may assist in leaf changes but is not mandatory. The only constant and reliable factor from year-to-year is the shortening length of daylight. As days become shorter and nights grow longer, biochemical processes in the leaf initiate changes in color. The other factors vary annually, making the exact timing of peak fall foliage impossible.

What color is a leaf? Green, of course; ask any preschooler! True, but … this color is nothing but a mask of green pigment known as chlorophyll. The leaves’ real colors – shades of red, yellow, orange and purple – lie beneath. Chlorophyll needs light to maintain its color or cover-up. As daylight diminishes with each passing day so does the green color of leaves. One of nature’s most vibrant hidden treasures is revealed!

After a brief cooling, high pressure brings warmer temperatures for the weekend and next week.

“Fall days come swiftly, like the running of coyotes through the leaf-covered valley.”

~La Crescenta proverb

Sue Kilpatrick is a Crescenta Valley
resident and  Official Skywarn
Spotter for the National Weather Service. Reach her at suelkilpatrick@gmail.com.

  Sue Kilpatrick