MINNEAPOLIS (WCCO) — It’s a favorite time of year for lots of Minnesotans — the cool, crisp air of autumn and the changing colors of the leaves. Over the past few falls, Minnesota has been lucky to have a vibrant fall color season.
So, what makes colorful leaves? Good Question.
“What we really need are bright, sunny, warm days and cool nights without frost,” says Val Cervenka, forest health coordinator for the Minnesota Department of Natural Resources.
The warm September days allow the trees to continue producing sugars, which partly accounts for the brighter colors. The cool September nights lock in those sugars and slow down the production of chlorophyll.
Chlorophyll is what keep the leaves green through the summer and mask the color of the leaves underneath. Once that chlorophyll goes away, as the days get shorter and colder, the colors are revealed.
But, what’s most important for a vibrant season is the what’s already happened — a wet summer. The water in August kept the trees healthy and continuing to produce chlorophyll when they should.
“So far, we’re heading into what looks like is going to be a great fall color season,” says Cervenka.
The DNR says there are some spots in northern and western Minnesota where leaves have started to turn. In the metro area, it’s not expected until the end of September. Any trees that might already be colorful in the metro area are likely not fall colors.
“If you go up north an see the red trees, that might be fall colors, but if you see them here now, I don’t think so,” says Cervenka. “Those trees are probably under stress, either too little moisture or too much moisture or some other thing is going on.”