Dieffenbachia plants usually grow well without fertilizer. a student wanted to see if adding liquid fertilizer would make a difference in the growth of the plant. three plants were placed in the same type of pot with the same type of soil. two plants received fertilizer and one plant did not. all plants received the same amount of light and water during the experiment. she watched the plants grow over a period of 30 days, only adding the same amount of water to each plant on a weekly basis.