Maryland Code, Local Government § 4-416

(b) Without the express approval of the county commissioners or county council of the county in which the municipality is located, for 5 years after an annexation by a municipality, the municipality may not allow development of the annexed land for land uses substantially different than the authorized use, or at a substantially higher density, not exceeding 50%, than could be granted for the proposed development, in accordance with the zoning classification of the county applicable at the time of the annexation.

(c) Notwithstanding § 4-204 of the Land Use Article and if the county expressly approves, the municipality may place the annexed land in a zoning classification that allows a land use or density different from the land use or density specified in the zoning classification of the county or agency with planning and zoning jurisdiction over the land prior to its annexation applicable at the time of the annexation.