How Does Spring And Summer Weather Impact Fall Colors?

The start of autumn and the start of the fall color season for those who love a road trip to their national forest or hometown park to see the changing of leaf colors in the autumn months.  And they're perhaps no more known representation of this phenomenon than in the forests of New England. 

“You can see widespread swaths of these hardwood trees such as sugar maple, American beech, yellow birch, paper birch, ash. They're all turning color as the fall season progresses.” 

What Determines When Leaves Change?

Revealing various shades of gold, red and orange, according to Amey Bailey, a U. S. Forest Service technician in New Hampshire.   Yet have you considered that perhaps the weather of the spring and summer plays a key role in the whens and hows of changing leaf colors and times the view such.  Bailey takes her home region as an example. 

“Usually what makes really brilliant color is a summer that's been somewhat moist. So, the trees are healthy, and the nights are getting long and are getting colder. And then a sunny day that's going to allow the leaf to still make some sugars, and the sugars are going to help keep the leaf on the tree and expressing these colors that are now available.” 

Yet regarding weather earlier this year in New England. 

“We got approximately 24” of rain in April, May and June, which is twice what you usually get.” 

A Wet Spring Not Good For Fall Colors

And because foliage began to develop during this wet period. 

“There was a lot of little fungal spores in the atmosphere being splashed off the soil that we're landing on these newly unfurling leaves and insects were hatching and so many of our tree species were attacked by fungal and insect problems which caused the leaves to be burnt and shriveled and rolled and not their full leaf size this year.” 

That was followed by an extreme heat event underway since July, producing drought conditions. 

“These trees are just kind of completely stressed and maxed by this heat and drought.” 

The result regarding fall colors, it depends on the tree species and the landscape.  Some trees are undergoing a premature transition to the reds, yellows and oranges.  Others, especially those either with fungal or pest damage or rooted in shallow soils, reveal a brown color. 

“We haven't had any below freezing temperatures yet, but we have a lot of color change on the landscape. And this has to do with the drought and the poor conditions that the trees have had based on the early spring conditions.”