Common geraniums (Pelargonium hortorum) are a favorite bedding plant with home gardeners. They are used to add instant, seasonal color to the yard or containers. Geraniums range widely in their growing habits and appearance, according to Clemson University. Some are trailing plants, while others grow tall and bushy. Geraniums are classified as annuals because they are not usually able to survive in the ground during freezing temperatures, but there are ways to over-winter your geraniums.
Plant geraniums in the spring, when all danger of frost has passed. The University of Minnesota recommends waiting until the temperature of the soil is at least 60 degrees Fahrenheit. Geraniums grow best in soil that is rich, loamy and well-draining. The planting site should be exposed to a minimum of eight hours of sunlight per day, or the plants will not bloom well.
Water geraniums by digging a trench around the planting site to catch the water and hold it until it is absorbed by the ground. Water generously, until the water stops sinking into the soil. Then, let the surface of the soil dry out to the touch before watering again. Otherwise, the ground may become overly saturated and the plants may develop root rot, a fungal disease that will destroy the roots and kill the geraniums. In addition, keep an eye on the blooms. If the flowers begin to wilt, they need to be watered more frequently, according to the University of Minnesota.
Geraniums can be over-fertilized, so it's better to err on the side of too little fertilizer than too much. Mix two tsp. of a balanced (20-20-20), water-soluble fertilizer into one gallon of water. Use this mixture once every three weeks as a substitute for a usual watering. You do not have to use the whole gallon of water if you are only watering a small number of plants.
Maintenance and Problems
Deadhead (remove from the plant) the flowers often to encourage re-blooming. Also pluck off any dried or brown flowers, as decaying plant material will attract the Botrytis fungus. Pinching back new growth can encourage a bushier form, according to Clemson University. Insect pests are not usually a problem on these plants, but fungal diseases can be a problem. Keep water from sitting on the leaves by watering at soil level and by making sure the plants have enough air circulating around them to dry them out quickly after rainstorms. In addition, fungicides can be sprayed on the plants in the spring to prevent fungal diseases.
Geraniums will not live if exposed to freezing temperatures, according to the University of Illinois. In cold climates, they should be planted in containers and brought indoors well before the first frost of the season. Place them near a bright, sunny window during the winter months.