Though September shows us much with all of the migration of birds, maturing of apples and other fruits and a plethora of mushrooms in the woods, it is the trees with their colorful leaves that grab our attention the most.
The typical sequence of events is that most of the trees begin the month with green leaves. Shortening of daylight hours as we approach the autumnal equinox, causes the breakdown of green colors (chlorophyll) in the leaves and other colors, mostly yellow and red, will take over.
Yellow (xanthophyll) was present all summer, but masked by the dominant chlorophyll. Red (anthocyanin) is formed during the waning days of summer from excess sugars in the leaves.
As we go through the weeks of September, these two colors, often combined with some orange (as in sugar maples) and purples (frequently in dogwoods), give us quite a show. The colors seem to blend together best and reach a peak by late in the month.
The month-long arboreal show is spaced out with different kinds of trees. Early in the month, the small sumacs, pin cherries and dogwoods develop red leaves. Among the yellows, poplars, birches and ashes set the pace.
ADVERTISEMENT
As we continue through the weeks, more trees join in the performance. Soon, red maples, sugar maples and red oaks add more to this color. Basswoods, elms, ironwoods and finally, quaking aspens, continue the yellows. It becomes quite a show by the time these colors have all appeared in the Northland.
Though providing quite a spectacle that brings us back annually to observe, the lives of these leaves are waning and will be of no further use to the trees. They will soon drop.
Again, this leaf fall is long and varied, but the largest amount of the drop happens in October, at or about the middle of the month.
Sometimes abruptly, a wind or a rainy time will bring down the leaves and we find ourselves in a world surrounded by woody deciduous trees devoid of their leaves. This is the normal scenario, but there are some variations.
An exception to this pattern was revealed to me as I was biking in the early days of September. Along the trail, nearly all of the trees still held their summer green attire, but out in the open, I saw a few small trees that had gone a step beyond that.
Leaves on these trees were not colorful, they were not present at all. I stopped for a closer look and saw that these small trees, hawthorns, had already dropped all of their foliage. The trees were not sick or dying and held a very rich growth of their products of the season.
Hawthorns - cousins of the apples - produce small apple-like fruits, sometimes called "haw apples." Each branch was loaded with these bright red small fruits, about one-half inch in diameter, among the well-known thorns. Hawthorns are a diverse group and not all species drop leaves at this time; nearby, others were fully green.
Why would they drop their leaves so quickly, in early September?
ADVERTISEMENT
A possible answer to this question is the fact that with no leaves on the trees, the red fruits of the season are easy to see - no foliage blocking their view. Therefore, birds and small mammals will find them and so disperse the seeds within.
Before long, other trees of the Northland with red fruits - highbush cranberry and crab apples - will follow this route of defoliation. But it begins in early September with the small hawthorn trees.
Retired teacher Larry Weber is the author of several books, including “Butterflies of the North Woods,” “Spiders of the North Woods,” “Webwood” and “In a Patch of Goldenrods.” Contact him c/o krohman@duluthnews.com .
