The weather is forcing foliage to fall faster and other areas are thriving

But some of the same New England areas that have seen drought conditions report clear fall colors.

“We see exceptionally vibrant leaves in Vermont this year,” said Dr. William Keaton, professor of forest ecology and forestry at the University of Vermont. “It’s a combination of factors including last year’s good tree growth, mild drought and warmer months and colder nights last month.”

Drought may trigger more vibrant colors and time may be premature.

“This year’s colors are coming two weeks earlier than normal, and they’re going fast and furious,” Keaton said. “Often, drought creates stress for trees – physiological stress. So from that standpoint, drought may exacerbate some of the colors, stress is not a good thing, and it could be a precursor to things to come.”

Not only does it start early, but the duration of leaf color can also be affected.

“As for the fall leaves, the drought leaves may change color earlier, but they may die earlier,” said Caitlin Weber, data analyst at the Climate Center. “Prolonged and severe drought can cause physical damage to trees such as root loss and slow growth, and make it harder for trees to protect themselves from pests and diseases.”

That is why the extent of drought is also important.

For example, Vermont is often in moderate drought (level 4 in 1), as opposed to New Hampshire, Massachusetts and Maine, which are often in severe drought (level 4 in 2). Rhode Island is almost completely under severe drought (Level 4 of 3).

“Moderate and moderate drought can actually increase the fall foliage somewhat, unless it leads to a lot of‘ browning ’or early leaf fall,” Keaton said. “Then, one year of drought means less strong leaf production next year.”

So this is not always an immediate impact. Often, the effects of drought are delayed. Currently, 76% of Vermont is under moderate drought conditions or worse. But at the same time last year, the state was in a 0% drought.

“Last year’s good tree growth allowed the trees to store energy reserves and nutrients for the winter, resulting in strong leaf growth this spring and summer,” Keaton said. “But it works the other way around … one year a bad drought will be poor green next year.”

Extreme heat and climate change

The best conditions for vibrant foliage include hot days and cold nights. It promotes the production of a chemical called anthocyanin, which adds red and purple to some species, such as maples.

“Different temperatures between night and day accelerate the loss of chlorophyll from the leaves, which leaves secondary photosynthetic pigments (carotenoids) that give yellow and orange colors,” Keaton said.

However, as with drought, extreme heat can cause the trees to brown prematurely or lose their leaves. Moderate heat or prolonged heat – when the fall feels like an extension of summer – can delay the fall of colors because the trees do not receive a signal that the fall has come.

“Plants are likely to lose this note completely and lose leaves quickly,” Weber said.

Western states such as Colorado and New Mexico often see tourism incentives as travelers search for the clear leaves of aspen and scrub oak trees. Those two states, along with Nevada and Utah, recorded the hottest August in August of this year. New Mexico recorded its second dry summer (June to August).

“The reasons why fall is green are complex, in fact they are not fully understood,” Keaton said. “Drought is one of many factors, the other is the difference between daytime and nighttime temperatures in photosynthesis and autumn. All of these show just how attractive our forest ecosystems are!”

Wildfire adds another obstacle / embarrassment

Wildfires will complicate leaf burning in Colorado and California this year. Many states are still dealing with poor air quality and dim skies from the smoke. That fog will hinder your ability to see vibrant colors.