The science behind Fall Colors is fascinating. This season has a recipe for a good show, but with a couple of factors indicating a shorter color session. We interviewed Dr. Danica Lombardozzi, an Ecophysiologist with NCAR, and she helped us come up 13 interesting facts about the Autumn Show.
1. Leaves have timers that are triggered by the Summer Solstice, in late June. That's the day the nighttime starts to catch back up with the daylight.
2. Leaves are already yellow, orange, and red. The green is just a temporary mask made of chlorophyll.
3. Cells and veins on the base of the leaves start to close off, restricting nutrients and photosynthae from reaching the plant. Photosynthesis breaks down and that green mask is removed.
4. Fall Colors arrive at about the same time every year because it is the length of the night that changes the leaves, and the night time hours are the same every year.
5. Temperature can play a role as well. Cooler temperatures can trick a plant into believing that the nights are longer than they are. This is why leaves tend to change at the higher elevations first. Warmer days, like this year, mean the Fall Colors will arrive just a little bit later than normal. Temperature usually only changes the timing by plus or minus 1 or 2 weeks.
6. Warm days, cool nights, and steady moisture is the best weather recipe for brilliant, long lasting colors.
7. Warmer days can result in darker oranges and reds. The warm days allow the plants to make sugars that get left in the leaves, and that is what creates the redder colors.
8. Colorado doesn't get a lot of reds because Aspens and Cottonwoods are the main source of our colors. These trees have leaves that are usually brilliant yellows and golds.
9. The peak of the Fall Colors in Colorado is just after the Autumnal Equinox. That is the day that the night time hours equal the day time hours.
10. A very wet spring can cause some disease that could shorten or dull the Fall Color season. This was the case for us in 2015. Fungal Leaf Spot disease has been detected in some aspens and cottonwoods.
11. Dry conditions in the late summer can cause leaves to change a little earlier. This has been the case at the lower elevations on the Front Range this year. Don't be surprised if your trees change a week of two earlier than they did last year.
12. Plants have different personalities, just like humans are all different. Some will turn their leaves at the first sign of light or temperature change, and others will wait a little bit longer. That could explain why one tree in your yard has already changed while other identical trees have not.
13. An early freeze or snow usually spells the end of the color show. This fall has a slightly higher chance of that happening, so you might want to make sure you hit that peak time between September 20 and the first week of October. Though there is nothing more beautiful than fall colors contrast with an early dusting of snow.