It shall also be the duty of the Planning Commission to recommend to the City Council from time to time such amendments, changes, supplements, modifications and revisions in the present Zoning Code of the City, including a zoning plan or plans for all lands and territory which may be added to the City hereafter from time to time, for the control of height, area, bulk, location and use of buildings and premises, to carry out proper City planning, but a public hearing shall always be held by the Planning Commission before a zoning plan or any amendments or supplements thereto are recommended to the City Council. (1981 Code § 5.6)