Brightly colored flowers and distinctive foliage make geraniums a favorite among gardeners. They are one of the easiest plants to cultivate either indoors or outdoors. Geraniums are available in a multitude of colors, and their banded leaves vary in color and pattern as well. Under the right conditions, geraniums will bloom from early spring until the first frost.
Optimum Indoor Conditions
Geraniums make eye-catching houseplants and can add a cheerful touch to any home. While geraniums prefer bright light, such as in a window or under a grow light, they will subsist under moderate lighting conditions. Plant geraniums using potting soil in a pot that drains well. Water weekly. Apply a water-soluble fertilizer each month during spring and summer, and every other month during the cooler seasons.
Optimum Conditions for Outdoor Pots
Potted geraniums can flatter entranceways, porches, steps, and decks with a splashes of color. Geraniums are fast growers, so to avoid the need to transplant them, plant them in pots at least 12 inches in diameter. A pot this size or larger will ensure sufficient space for the root system to develop and for water to be retained during dry spells. Be sure the pots are designed to provide good drainage. Plant in a mix of garden soil and peat moss, or in potting soil. Mulch with two inches of bark, and water weekly. Fertilize monthly using a tsp. of water-soluble 20-20-20 fertilizer per half-gallon of water.
Optimum Conditions in the Garden
Plant geraniums in garden beds in the spring, after the threat of frost has passed. Geraniums prefer full sun. They will live in partial shade, but growth and flower production will suffer. Geraniums prefer mildly acidic soil with a pH of at least 6.5. You can have your soil tested at your local extension center. According to the North Carolina Cooperative Extension Service, if a soil's pH is less than 5.5, adding lime will raise the pH sufficiently to keep your geraniums in peak form. Add compost to ensure proper air circulation and drainage. Cover planted geraniums with 2 inches of bark mulch. Fertilize monthly with a water-soluble 20-20-20 ratio of 2 tsp. of fertilizer per gallon of water. Water weekly under dry conditions, or install a drip irrigation system.
Geraniums will not survive most winters outdoors, as a single hard frost will destroy them. While some gardeners prefer to plant new geraniums each spring, others choose to protect the plants indoors during cold conditions. Excavate your geraniums before the first frost and plant in pots with holes for proper drainage. Place the pots inside near a sunny, south-facing window or under a grow light. Water weekly and apply a water-soluble fertilizer every other month. Replant or move pots back outside in the spring once the threat of frost has passed.
Like most plants, geraniums can fall prey to a broad range of diseases and pests. Many problems can be resolved by simply moving the plants to a sunnier location and watering the plants early in the day so the leaves can dry in the sun. Insecticidal soap, horticultural oils, miticides, and copper fungicides are recommended to treat diseases specific to geraniums and to eliminate insects. Contact your local extension center for solutions to specific problems.