Every question you've ever had about fall colors answered

Cory Reppenhagen schools us on fall colors in the high country

KUSA - The fall leaves are now at peak color in the Colorado high country, but time may be limited to see that show.

A few windy days (Tuesday and Wednesday) and a winter storm on Friday, Saturday, Sunday, and Monday, could bring down most of the leaves.

Colorado fall colors guide: where and when to see the best fall foliage

This weekend will likely not be pleasant for leaf peeping. There may even be a Winter Weather Advisory, or even a Warning for Sunday.

“If you get a good wind storm, a good rain storm, or a snow storm, it’s just gonna cause the leaves to fall off," said Dr. Danica Lombardozzi, a plant ecophysiologist with NCAR. She’s a leaf expert, and she helped 9NEWS put together this interesting nine lesson factoid on the science behind fall colors.

Lesson 1

The leaves die and fall to the ground, due to an energy management decision by the tree. It’s more effective to shut off the lifeline to the leaves, and shed them, than it is to devote energy to keep them alive in the winter.

Lombardozzi says the leaves have a weak connection to the tree, shortly after they turn color. “It just slowly starts to cut off the base of the leaf, and so that’s why, if you get a good wind storm, because those leaves aren’t attached quite as well anymore, it will just blow all the leaves off.”

With high winds, and more snow headed to our mountains this weekend, you might want to try get out on that fall color drive before Saturday.

Lesson 2

The green is just a mask. When photosynthesis is weakened. The leaf is able to remove that mask, and reveal its true colors. Yellow and Orange.

"The yellows and the oranges are underneath the chlorophyll all along, and the reds are created in the fall. They are produced because there are excess sugars in the leaves," said Lombardozzi.


Lesson 3

The leaves are on a timer, and the alarm is set for June. The Summer Solstice is the first signal for the plants.  They know that the days only get shorter after that. The backup alarm is set for the Autumnal Equinox. That’s when the night catches back up with the day.

"The plants do sense that. I don't know that they can detect that first day, but that is when they start to get less sunlight than the day before," said Lombardozzi.

Lesson 4

The timing of the color change in the Colorado mountains is like old faithful. You see the first signs in mid August, and it peaks by the middle of September. The leaves can start changing a week, or sometimes two weeks early, but the peak is always the same.

Lesson 5

Daylight is the key to the door, from summer to fall, not the temperature. As the days get shorter, photosynthesis slows due to the lack of sunlight.

“Temperature can modulate that response, and so that can push the color change a week earlier or maybe a week later, depending on how extreme the temperatures are, but day length is the typical cue,” said Lomardozzi

Lesson 6

Evergreens are not ever green. They turn in the fall as well, but needles live for two to three years, so only about a third of them die and fall off each year. The color is not quite as brilliant. They just turn a dull brown.

Lesson 7

The peak of the Colorado colors is different depending on location. The bulk of the central mountains peaks from Sept 15 through the 25th, the western slope is early October, and the I-25 metro areas and the San Luis Valley peaks in mid October.

Lesson 8

Temperature, drought and disease can throw off that timing, or diminish the vibrancy of the colors. Drought in the spring or early summer, or leaf disease, can make the colors appear dull, and call shorten the length of the display.

Lesson 9

The lower elevated metro area can have some of the best color because there are many trees that have been imported from the east coast that have more reds and dark oranges

© 2017 KUSA-TV


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