Southern California vector control districts have developed a list of backyard plants that are known to harbor roof rats. These plants are common plants that you will find at your local nursery. Consideration should be taken when planting these ornamentals, as they provide food and/or nesting sites for these rats.
Those plants are:
Algerian Ivy (Hedera canariensis)
Baccharis or Dwarf Chaparral Broom (Baccharis pilularis)