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Trees/Why do tree leaves change color in summer


Wondering if you could settle an argument? At my golf course in Cottam, Ontario, Canada (Belleview)there are about 5 silver maple trees around the course that about 3 weeks ago started turning to their fall colors.
Our foursome was waiting to tee-off on the 15th and we were commenting about the trees, two of which were to the right of the tee box. One buddy said "the reason the leaves were doing this was the tree thought it was fall because of all the rain we received in July" ("the trees thought it was fall because it's wettter in the fall").
 I told him don't think so, leaves turn color because of diminishing sunlight. I told him I didn't know the reason for the change but I'm positive it's not his theory.
Could you help us out please?  
Was thinking maybe stressed because of all the rain.

Thanks for your help

You are correct--the leaves manufacture food through a process of photosynthesis.  Plants use sunlight to turn water and carbon dioxide into oxygen and glucose. A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color. Photo meaning light. As the days get shorter and the temperature get cooler the leaves start to lose the chlorophyll and the colors of red and yellow show instead of the green. The moisture in the late summer or spring will effect the brilliance of the colors but not the timing . In dry summers the leaves may turn a little earlier than wet summers --more just dry up than turn. The change in the hours of sunlight triggers the leaves to turn. Tress of the same species may turn at different times due to genetic differences but the light is the key.  


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Jim Hyland


I am an expert in Forestry, Forest Entomology, Forest Pest Control, and Forest Health. Extensive knowledge in Identification of insects and diseases of trees. Expert on Bark beetles and other insects that attack forests. Also a Registrated Forester with extensive knowledge in the management and care of forests.


34 years as State Pest Management Chief in a Southern state. Extensive knowledge in Forestry.

BS with major in Forest Management and Entomology
Registered Forester
Certified Pesticide Appicator

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