As a horticulturist, you must have in-depth knowledge of fertilizers and pesticides. Your duties also might include placing orders for proper materials and other plant supplies. Thus, interviewers might ask you about fertilizer programs you developed and started for areas such as parks, sports arenas and business complexes. You can also expect them to quiz you about the various methods for controlling pests. Here, you'll talk about weighing options such as pruning, mulching and even replanting before turning to chemicals. You'll also discuss selecting chemicals least harmful to humans and the environment.