Geraniums produce bright flower heads atop tall slender stems that float above the foliage. Although they appear to be one large bloom, geranium blooms are actually a cluster of tiny flowers that make up the flower head. These short-lived perennials survive for several years if over-wintered properly. The key to growing vigorous plants with vibrant blooms lies in proper fertilization.
Plant geraniums in soil rich in organic matter. A 2- to 3-inch layer of well-rotted manure or compost improves drainage and provides nutrients to growing plants. Fresh manure robs the soil of nitrogen as it decomposes and should be avoided.
Apply slow-release or water-soluble fertilizer with a balanced formula like 10-10-10 or 8-8-8 once a month. Fertilizers high in nitrogen (the first number in the formula of fertilizer) produce lush foliage but often inhibit blooming.
Dilute fertilizer to 1/4 to 1/2 strength for geraniums grown as houseplants and apply every two weeks to provide a steady source of nutrients.