You or they could inquire with the Watershed Planning and Restoration agent in the Baltimore City Extension office, or the local Soil Conservation District office. As for what species to plant, outside of choosing native species in general, we'd just suggest matching any preferred species to the site conditions. Resources like those below are not exhaustive, but provide a good starting point for species more easily obtained from nurseries.

• Native Plants for Wildlife Habitat and Conservation Landscaping: Chesapeake Bay Watershed by the U.S. Fish and Wildlife Service
  • the Chesapeake Bay Native Plant Center has essentially a web-searchable version of the above publication, so someone can select sun vs. shade, soil traits, etc., to narrow-down which species should do well on a certain site
• Native Plants of Maryland by UMD Extension
• Landscaping with Native Plants by the Maryland Native Plant Society
• Native Plants for Northern Virginia (still applicable in much of MD)

Miri