Mass. Gen. Laws ch. 41 § 106
If the town provides by vote or by-law that the tree warden shall be appointed, such appointment shall be made by the board of selectmen. The term of such appointment shall be for three years.
In any city or in a town which exceeds ten thousand inhabitants and which provides by vote, by-law or by ordinance that the tree warden shall be appointed, such appointment shall be made by the mayor, with the approval of the city council or by the board of selectmen. In such city or town, the tree warden shall exercise the duties of tree warden and of insect pest control. Such tree warden shall be qualified by training and experience in the field of arborculture and licensed with the department of food and agriculture in accordance with the provisions of section ten of chapter one hundred and thirty-two B. The term of such appointment shall be for three years.
Mass. Gen. Laws ch. 41, § 106