Valued for its handsome leaves and long-lasting, brightly colored blooms, the geranium (Pelargonium spp.) is widely grown across most parts of the country. Although geranium is most often grown as an annual, it is perennial in U.S. Department of Agriculture plant hardiness zones 9 and 10. The geranium reaches a height of 6 to 36 inches, depending on the variety. This sturdy plant produces masses of blooms until the first frost in autumn.
Plant geraniums in a spot where the plants receive at least six to eight hours of sunlight per day. Without sunlight, blooming is decreased, and the plant is susceptible to diseases such as bacterial blight and rot. The exception is in extremely hot climates, where geraniums benefit from shade during the warmest part of the afternoon.
Pinch a newly planted geranium as soon as the plant is established and showing new growth, using your fingernails or pruners to remove about 1/2 inch from the tip of each stem. Pinching forces the geranium to branch out, creating a full, bushy plant. You can pinch the plant additional times to create even bushier growth; however, each pinching delays blooming.
Fertilize geraniums every week because the plants require a consistent supply of nutrients to bloom continuously throughout the season. Use an all-purpose, balanced water-soluble fertilizer applied at a rate of 1 tablespoon to 1 gallon of water.
Deadhead wilted blooms throughout the season. To deadhead, pinch the spent bloom along with the stem down to the next bloom, stem or bud. Regular deadheading, which prevents the geranium from going to seed early, is one of the most important steps to ensure the plant continues to bloom for as long as possible.
Water the soil at the base of the plant and avoid overhead watering because wet leaves create moist conditions that foster disease. Water deeply, wetting the soil to a depth of at least 6 inches, and don't water again until the soil is dry. If your geraniums are in containers, water slowly at the base of the plant until water drips through the drainage hole.