Question 574595
Use the combination formula (since order of the plants chosen does not matter)


C(n,r) = (n!)/(r!(n-r)!)


C(18,12) = (18!)/(12!*(18-12)!)


C(18,12) = (18!)/(12!*6!)


C(18,12) = (18*17*16*15*14*13*12!)/(12!*6!)


C(18,12) = (18*17*16*15*14*13)/(6!)


C(18,12) = (18*17*16*15*14*13)/(6*5*4*3*2*1)


C(18,12) = (13366080)/(720)


C(18,12) = 18564


So there are <font color="red">18564</font> different ways