Fall’s paintbrush could arrive early in DC

by Marlene Berlin

The leaves on my backyard dogwood trees are usually turning brown by this time of year, scorched by the dry late summer conditions. Instead, they’re turning red.

Marlene’s backyard dogwood.

I also realized my front yard, which usually requires a rake at least once if not twice a week by mid-September, has not required any attention. The tulip poplar, notorious for dropping its leaves early, is still lush and green.

Marlene’s tulip poplar.

And on my walks through the neighborhood and beyond, I started noticing more hints of fall color. It’s as if red and yellow dripped from a paintbrush onto the trees.

I don’t usually see this much color until well into the fall. I also don’t recall anything like the drenching we received in July and August. So I wondered if our unusually wet summer had anything to do with it.

From July 1 to August 15, The Washington Post’s Capital Weather Gang says, more than a foot of rain fell on our area – twice the average.

“All in all, since July 1, we’ve seen eight rain events across the metro area, each spaced about a week apart. Five of those surpassed an inch of rain at Reagan National Airport. One ranked among the all-time great rain events of July.”

The weather that followed was strangely cool. “The coolest start to September in 82 years,” said the Capital Weather Gang.

Does this explain the early color changes, or the leaves of my tulip poplar holding their green? I asked Vera Ertem of DDOT’s Urban Forestry Administration and Ranger Bill Yeaman of the National Park Service.

From Yeaman, no theories. But he did send photos of colors he is beginning to see in Rock Creek Park:

Witch hazel in yellow (left) and a touch of red on a black gum (right).

Ertem sent me this flyer from the International Society of Arboriculture. It explains:

Colors most affected by weather are the red tones created by anthocyanin. On warm sunny days lots of sugar is produced in the leaves. Trees exposed to brighter sunlight generate the reaction between the anthocynanins and the excess sugar creating the bright red hue.

Cooler temperatures cause the veins in the leaves to gradually close preventing the sugars from moving out which preserves the red tones. Thus a succession of warm sunny days and cool crisp nights can paint the most spectacular display of color.

The level of moisture in the soil can also affect autumn color. A severe summer drought can delay the onset of color change by weeks. Ideal conditions for producing the most brilliant colors are a warm wet spring, favorable summer weather, and sunny fall days with the cooler temperatures at night.

So it appears we’re in for a brilliant show of color this year – and early, too.