Freeze Nips Colors

by Marlene
The cold snap that gripped the valley a couple of weekends ago is gone and with it are the sunshine yellow, pumpkin orange, and crimson red leaves that have captivated me each fall. Record low temperatures in the Flathead Valley and 6 inches of snow in Kalispell have nipped the colorful shades of autumn in the bud.
The freeze has killed the leaves causing them to turn brown and fall off before they had a chance to change.
The good news is that the cottonwoods, birch, and maple trees will survive as they had already produced sap and water to fill their root systems prior to the deep freeze.  The bad news is that little in the way of brilliant color will be evident this year.
The leaves are dropping more each day in dreary shades of tawny to drab brown.  Perhaps the tamaracs will turn yellow, but it doesn’t appear to be a particularly good year for that either.
Pigments such as chlorophyll, carotenoid, and anthocyanins are natural substances produced by leaf cells. Chlorophyll produces the bright green leaves we see in summer. It is most important as it uses the process photosynthesis to produce food for the trees. Carotenoid is always in the leaf but is covered by the chlorophyll. It absorbs light enegry for use in photosynthesis and protects chloropyll from photodamage. It produces the yellows, oranges, and warm browns we see in autumn. Anthocyanins are not made in all trees and are only produced in autumn, under certain conditions. For example, warm sunny days and cool (but not freezing) nights. Cool nights prevent the sap from running down into the branches and trunk of the tree. This causes the anthocyanins to be alerted and protect the tree and allow it to recover nutrients before the leaves fall off for the winter.

Going from fall to winter overnight was a bit unusual for Northwest Montana and single digit low temperatures made for a real October surprise.


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