Fall foliage on Long Island: Why the season might be extended this year

Climate change may be one reason, as the nights have stayed warmer longer than usual, explained Lehrer, cautioning that confirming such trends requires decades of data.

Trees and plants respond to what botanists call "environmental cues," namely autumn’s shorter days and cooler nights, botanists said.

The chilly nightime hours temporarily prevent those sunset-rivaling pigments in the leaves from retreating to the roots.

"The cooler nights and gradual narrowing of leaf veins in the fall, means that a majority of the sugars produced are trapped in the leaf," Michigan University Extension explained in a 2016 web article.

Once the leaves have sent as many nutrients as possible below ground, a corky barrier slowing forming between the leaf and the stem closes off, allowing the leaves to wither, and blow away.

Daniel Weitoish, an arborist with Cornell University's Cornell Botanic Gardens, said by email the region's weather is becoming harder to predict on a year-to-year basis.

"Late frosts, summer droughts, or unusually wet years have all impacted the timing and brilliance of fall foliage over the last 5 years," he said.

Of course, there are complicating factors. For one, different species answer more strongly to one signal or the other. "Some are more responsive to day length; some are more responsive to cooler temperatures," said Lehrer.

The chill causes trees to prepare for winter by sending sap down to the roots, scientists said, and switch from making green chlorophyll to sugar with its multicolored pigments.

If the nights remain mild, the veins in the leaves stay open, allowing that sunset-rivaling sugar to exit, botanists said. Cold, however, helps seal those veins shut.

How late was the first "hard" frost?

Exact dates are not known. The National Weather Service tracks temperatures; the first "hard" frost is declared once thermometers drop to 32 F or below.

"This year, we were about a week later, which isn’t crazy," said Jay Engle, a weather service meteorologist based in Upton. Thermometers fell to 31 F as early as Nov. 6, three degrees below the low seen on the 4th and 5th, he said.

On average, temperatures fall to 32 F on Nov. 1 "for all of Suffolk County and also northern Nassau; for southern Nassau, it is on Nov. 11," Engle said, citing records that started in 1963.

In a word, yes. Perhaps surprisingly, the yellows and oranges eclipsed by the green chlorophyll all through spring and summer, are actually there all along.

The reds and purples, however, explained Farmingdale's Lehrer, are not produced by maples, dogwoods and gum trees until late summer and the fall.

"So you would expect that purples and reds would be sort of muted this year because we've had this late onslaught of cooler temperatures."

Further, said Todd Forrest, The New York Botanical Garden’s Arthur Ross vice president for horticulture and living collections in the Bronx, by email. "The late fall colors tend to be more in the golds and ambers rather than the scarlets, although there are some exceptions."

Naturally, whether a leaf-withering frost develops in part depends on how clear the skies are, as clouds can trap heat. "A hard frost, or lots of clouds, will lessen the display a bit," Forrest said.

"Last year wasn't so spectacular," recalled Bush, Old Westbury's horticulturist, " … because we didn't have what would always be thought of as a gold Northeast autumn, warm, 50 to 60 degree days, and nights going into the 30s and 40s."

Those ideal conditions skipped this season too. "I think that's the factor that is probably causing the not so spectacular foliage," Brush added.

At least this autumn's leaf peepers should gain time. "We could have fall colors as late as Thanksgiving," thanks partially to the late frost, said Vinnie Simeone, director, Planting Fields Arboretum, in Oyster Bay.

"Last year was a little more compressed," he recalled. This year, he said, has been spotty, a pattern that may continue. "We had some fall color; then a lull; then some more fall color."

His prediction? " I think you're going to see a lot of trees still have their fall color and drop their leaves a little later."

Well, for starters, it was a glorious spring for blossoms, thanks partly to all those downpours.

"We had a wonderful, wonderful spring flower season, and I actually kind of wonder whether that extra (rain) has then helped plants stay greener," noted Alejandro Saralegui, director, at Sagaponack's The Madoo Conservancy, a nonprofit.

And now, "There's definitely a noticeable change in the health and what one could call the productivity of the plant." Or in gardening lingo: "Everything is fruiting better; crab apple (trees) have many more crab apples," he said.

Both invasive Norway maples and Callery pears, two trees known for intensely crimson foliage, tend to hang onto their leaves until around Thanksgiving, said Lehrer. And the very first branches that grew on a beech tree may keep their leaves until spring, a phenomen called marcescence.

So don't count this season out yet. "If the weather remains bright and cool during the day and cold (but not freezing) at night, we should have good color for the next few weeks," said The New York Botanical Garden expert, adding:

"Even a "meh" fall color year is still one of nature’s (and NYBG’s) great marvels."