Md. Code, Local Gov't § 27-309

(a) The designated officer shall summon or cause to be summoned any respondent that is known to the designated officer or to the board of viewers. (b) (1) If the designated officer finds by affidavit or otherwise that a landowner whose name is unknown cannot after due diligence be determined by the petitioners, the designated officer shall summon the unknown landowner by publishing the petition or the substance of the petition in a newspaper of general circulation in the county where the land is located. (2) The summons shall: (i) describe the land as to which the owner is unknown; (ii) include the order of the county commissioners or county council; (iii) include the date of the final hearing that will be held before the county commissioners or the county council establishes the drainage district; and (iv) be published for 4 successive weeks before the date of the final hearing.