LA CROSSE, Wisconsin (WXOW) - Brilliant fall colors are an asset to the Coulee Region. But this year some trees are dropping their leaves early.
"There are a couple of trees that have lost half of their leaves already," said Tim Gerber, Biology Professor at UW-La Crosse. "Not most of them, but there are a couple."
The reason behind this is the very dry conditions this summer.
"Usually what plants do if they don't have enough water is their leaves wilt," said Gerber. "So they look droopy on the plant. And then if they don't get enough in extreme conditions some plants just drop their leaves."
Gerber said this is because trees lose water through their leaves. By dropping the leaves, the plant can conserve moisture.
But not all trees are feeling the strain the same way. The stress is greatest on very old, young, and already unhealthy plants.
"Plants that aren't as healthy, plants that are really under stress, they respond to their environment just like people do," said Gerber.
In a normal year, leaves change color when daylight starts to dwindle.
"Leaves have pigments in them and the most common pigment, or the most dominant pigment is chlorophyll which is green," said Gerber. "There are other pigments that will show red colors and orange colors, and yellow colors too. However, there isn't as much of them in the leaf so usually you see green. At the end of the growing season the chlorophyll is no longer manufactured in the leaf and so the other pigments start to show up."
And leaves drop due to hormonal changes in the plant.
"There's a layer of cells that grow between the leaf and the tree branch," said Gerber. "And so as those cells develop the branch is kind of sealed off and the leaf will fall off."
This year, while some trees are losing their leaves early, the far majority of them are still doing okay. But the color change may be lagging.
"They might be a little bit behind," said Gerber. "You usually see your colors at the end of September and then into mid October. So I don't know that anything is too far off. I mean, things are starting like it normally does, it's just the added stress doesn't help."
If you're interested in tracking the color changes across the Coulee Region you can visit the Travel Wisconsin website at http://www.travelwisconsin.com/fall-color-report the Minnesota DNR website at http://www.dnr.state.mn.us/fall_colors/index.html and the Iowa DNR website at http://www.iowadnr.gov/Environment/Forestry/ForestryLinksPublications/FallColor.aspx
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