It shall be unlawful for any person, owner or occupant having supervision or control of any lot, tract, parcel of land or portion thereof, occupied or unoccupied, improved or unimproved, within the corporate limits of the city to knowingly permit or maintain on any such lot, tract or parcel any tree or part thereof which is a nuisance, and it shall be the duty of such person, owner or occupant to promptly abate the nuisance of otherwise control such condition.