The trees in Sacramento sure have looked pretty lately, haven’t they?
Take a look around town — the Capitol, midtown, Sac State’s campus and other arboreal hotspots — and those colors do appear especially vibrant, even for the City of Trees.
A certified arborist says the trees’ popping may be partly illusion. The leaves might appear a shade brighter than usual, but they’re mostly catching our eye because they’re sticking around in trees later into autumn than they do in most years, Matt Morgan of Davey Tree Expert Co.’s Sacramento office said.
“Normally sycamore trees would have lost their leaves by now,” Morgan said. “I don’t think they’re necessarily more vibrant, but people are seeing them in a longer time frame.”
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Morgan estimated that those colorful leaves are usually at peak visibility for about two or three weeks, but have stuck around closer to five or six weeks this fall.
The reason has everything to do with the weather, Morgan said.
“Normally you’re seeing this leaf drop in October or early November,” he explained. “We haven’t had that cold weather” that leads leaves to drop, he added.
Generally speaking, the main factors contributing to leaf color in autumn are the weather and moisture levels in the soil, as explained in educational materials from the U.S. Department of Agriculture.
“A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays,” a pamphlet titled “Why Leaves Change Color” says. “During these days, lots of sugars are produced in the leaf, but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out.”
Those conditions describe this November in Sacramento almost perfectly. High temperatures have trended anywhere from 5 to 10 degrees warmer than average almost every day this month, while the lows have trended about the same magnitude in the other direction, according to National Weather Service and Intellicast data.
Nighttime temperatures have been cold and crisp, in the mid-to-high 30s most of the week of Thanksgiving, but haven’t dipped below freezing.
A lack of rain helps. Downtown Sacramento has seen less than an inch between May and this week’s showers.
There have also been few windy days up to this point in fall, which helps keep the leaves in the trees. And the leaves are a lot less pretty once they’ve been raked up and bagged.
Morgan said the city of Rancho Cordova is still waiting to clean up leaves that have yet to fall, a couple of weeks later than the usual time frame.
“Normally by this time, they’re done cleaning up sycamores,” he said.
So why is Sacramento’s treescape in particular so breathtaking this fall? We’re not the only city with warm days and cool nights, after all.
Well, we’re the City of Trees, that’s why.
An MIT study in 2017 confirmed that our nickname is no accident. By percentage, Sacramento (23.6 percent) ranked No. 5 among 20 world cities known for their tree canopy coverage. Cambridge, Massachusetts, was the only U.S. city surpassing Sacramento, at 25.3 percent.
And it’s not just sycamores that brighten up the Sacramento canopy. Zelkovas, Chinese pistache, red maples, walnut trees and pear trees all add to our palette, according to Morgan.
Smoke or worsened air quality from wildfires does not affect leaf color, Morgan said.
But comparatively speaking, the Sacramento area’s trees may look a lot more appealing with a clear backdrop than through a smoke-filtered lens.