Mich. Comp. Laws § 239.5

Sec. 5. It shall be the duty of every owner, occupant or person having charge of lands in this state, to cut or trim, or cause to be cut or trimmed, to a height not exceeding 4 1/2 feet and a width not exceeding 3 feet, all hedges or hedge rows along or on the public highway or adjacent thereto in each and every year, except such hedges as shall have been set out for the protection of fruit trees and nursery stock. Trimmings or brush from such hedge rows shall not be left lying within the limits of the highway, but shall be forthwith removed: Provided, That this section shall not apply to streets or highways within incorporated cities.