Fall Color 2010

It’s not a “figleaf” of your imagination…..foliage color for October 2010 here in Michigan has shaped up to be one of the best years for vibrant fall color. Why? I’m glad you asked…..let me throw in my 2 cents on the subject…. Our fall color show generally starts with plants like Ash, Poison Ivy and Sumac in late September and ends with Weeping Willow, Larch and Oak sometime in November. October is the prime month for the most vibrant of colors. It all started back on June 21 (the longest daylight day of the year). Since then the days have gradually been getting shorter and something called “photoperiodism” is how trees adjust their cycles to the change in the amount of available daylight. The process induced by photoperiodism is called “senescence” which is the collective process that leads to the aging and death of a plant or plant part like a leaf. The plant or tree is moving towards it’s winter nap called dormancy. When leaves appear green during the growing season it’s because they contain an abundance of chlorophyll. Chlorophyll is produced in response to sunlight and as the season and light levels change less chlorophyll is produced. Chlorophyll masks the other pigment colors. As the chlorophyll decomposes the green color fades from the leaves like a piece of green paper fades in the sunlight. Leaves containing primarily anthocyanins will appear red. Leaves with good amounts of both anthocyanins and carotenoids will appear orange. Leaves with primarily carotenoids or xanthophyll will appear yellow. Some leaves most notably Oak have “tannins” which are responsible for a less colorful brownish color. During the growing season chlorophyll is replaced constantly in the leaves. Chlorophyll breaks down with exposure to sunlight so the leaves must manufacture new chlorophyll. In Autumn when the connection between the leaf and the rest of the plant begins to separate (abscission layer causing leaf drop) the production of chlorophyll slows and then stops. Temperature, sunlight and soil moisture influence the quality of a fall color display. This is where the conditions in 2010 in Michigan have been ideal in my opinion. High pressure is our friend when it comes to weather. The sunny days and cool nights have been ideal for the formation of the red (anthocyanin) pigments in foliage. Unlike years when it’s cloudy and rainy, sunny fall weather and cool nights produce vibrant red and orange colors. Some years yellow is the predominant color….this year red and orange are nudging yellow for the spotlight in nature’s grand and final act of the growing season. Wind storms and heavy rains can also shorten the fall color season….this year calm weather and high pressure has suspended the color blast in the branches for our viewing pleasure. The heat and dry conditions caused some stress for some plants instigating the color as the days become shorter. These conditions followed by brilliantly beautiful and calm October weather giving anthocyanins equal billing with the carotenoids and xanthophyll have set us up for a color show to enjoy……get outside for some fresh air and bring your camera!

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