Gardeners often use plant foods and fertilizers to provide their plants with extra nutrients, but multivitamins made for human consumption can benefit plants when added to their water. Vitamins A, B1, B12, B100, C and E, as well as pantothenic acid, can help plants grow faster, grow taller, and resist fungi and insect infestations, according to Mother Earth News.
Choose a multivitamin or a combination of vitamins that contain about 50,000 I.U. of vitamin A, 200 mg of vitamin B1, 200 mg of vitamin B12, 200 mg of vitamin B100, 1,000 mg of vitamin C, 400 I.U. of vitamin E and 500 mg of pantothenic acid.
Use a mortar and pestle to crush the vitamins into a fine powder. Coarse granules won't dissolve in water.
Mix your vitamins with 14 qt. of water until they dissolve completely. If your vitamins don't dissolve in cold water, boil the water.
Water your plants with the vitamin mixture every few days.