The geranium (Pelargonium sp.) is a versatile, non-demanding plant that adds bright color to a flowerbed, patio container, hanging basket or window box from early summer until the first frost. While the sturdy plants are drought-tolerant and tend to be pest-free, geraniums are not a good choice a full-shade garden.
Although geraniums love the sun and are happiest with six to eight hours of bright sunlight per day, sunlight early in the day is preferable. The ideal garden spot for a geranium is a location where the plants are exposed to sunlight during the morning, as geraniums benefit from a few hours of afternoon shade during the hottest part of the day. Afternoon shade is especially important in hot desert climates with intense sunlight, where geraniums thrive in as few as four hours of morning sunlight per day.
Geraniums grown in too much shade sometimes survive, but the plants are tall and spindly and produce fewer and smaller blooms. Without sunlight and dry air, geraniums are susceptible to a variety of diseases caused by lack of light and moist, cool conditions. Fungal diseases, such as gray mold, black rot and various bacterial diseases nearly always mean the death of the plant. To prevent disease caused by moist conditions, provide enough sunlight and allow 15 to 18 inches of space between each plant.
While occasional dry periods don’t bother geraniums, the plants do best with regular watering. Water geraniums deeply, providing enough water to saturate the roots, then don’t water the plants again until the top 1 inch of soil feels dry to the touch. Geraniums in hot, dry climates require water more frequently than geraniums in cool or humid climates, but geraniums should never be in wet, muddy soil.
Geraniums grown in containers need a pot with a drainage hole in the bottom, as undrained soil smothers the roots and causes death of the plant. Use a loose, well-drained potting soil such as a peat-based commercial potting soil. Avoid garden soil, which becomes heavy and compacted and doesn’t allow proper air circulation or water absorption. Water containerized geraniums thoroughly and let the water run through the drainage hole, then don’t water again until the top 1 inch of soil feels dry. Geraniums grown in containers require water more frequently than in-ground plants, as the soil dries quickly. In hot weather, containerized geraniums may require water daily.