According to the University of Minnesota Extension, the best time to fertilize maple trees in northern Minnesota is as soon as the ground is workable in the spring until just before trees start growing in early May.
About this Author
Aileen Clarkson has been an award-winning editor and reporter for more than 20 years, earning three awards from the Society of Professional Journalists. She has worked for several newspapers, including "The Washington Post" and "The Charlotte Observer." Clarkson earned a Bachelor of Arts in journalism from the University of Florida.