Get ready for the fireworks
Scott Aker, head of horticulture for the U.S. National Arboretum, explains when fall leaves peak and why Western color is
the most spectacular in the country.
Q: How is fall color different in the West?
A: In the East, fall is like a really long parade from north to south. In the West, it’s like fireworks: a spectacular burst of beautiful colors over a short time. Here, the distribution of trees is based on altitude—different types of trees grow at different altitudes, with those at higher elevations developing color first.
Q: Why does altitude matter?
A: The timing of fall color is mostly controlled by the length of night—when that magical duration of darkness is reached, leaves begin to turn. How long the night must be depends on the tree species; trees that grow at high elevations must prepare for cold weather earlier, so they are programmed to develop fall color long before species that grow at lower elevations.
Q: How will this year’s drought affect the fall show?
A: The quality of the seasonal color is more complicated than people think—it depends on weather, and the plant’s health going into fall. With heat and drought, trees are often forced to give up some of their leaves to survive. So by the time autumn comes, there are simply fewer leaves to look at. Leaves of drought-stressed trees may turn brown instead of yellow or red, and drop off early to reduce water loss in the branches. You’re still going to see fall color, but it might not be as brilliant, or it may be more fleeting. Interior areas of the West that had decent monsoon rains may have better fall color than drier areas.