Fall Colors: When, where, and why

Weather

We’re finally headed into October, which means the leaves will soon transform into the stunning red, orange, yellow, & brown hues that make autumn such a spectacular time of year.

Here’s when fall colors *typically* peak across the area.

Losing Sunlight

There are several factors that affect the changing colors of leaves, chief among them being the sun.

As plants receive less direct sunlight and nights lengthen, their leaves stop producing chlorophyll, the chemical that creates the green color. This allows the other colored pigments within the leaves to show.

Weather’s Impact

The perfect recipe for brilliant autumn foliage is dry sunshine with cool nights.

This is where we’re not helping ourselves out much. September has been warm & wet, not the ideal version of early fall.

Sunny, dry days & cool nights speed up the production of sugars in leaves (a major part of those red hues), while rapidly getting rid of green pigment.

Rain showers are usually bad for autumn color because they cause many leaves to fall early.

A frost and/or freeze is actually harmful to foliage. Leaves are still alive as they change colors, so a killing frost damages the whole process.

A Short Window

No matter how much color we get, there’s only a few precious weeks of it before most trees shed their leaves altogether & we head toward winter.

Sources: Iowa DNR & U.S. Forest Service

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