### Clue: Direction signs installed in Louisiana plant (7)
### Answer: LOBELIA 
 ### Explanation: Definition: plant
  OBELI(plural of obelus, ÷, originally, in typography, the sign that gave the instruction,direction to delete unattested passages/words from writings, but now, it more commonly means the arithmetical operation of division) **contained in**(installed in) LA(abbrev. for Louisiana State in the US, used with postal codes).