Geraniums are one of the most popular flowering plants for home gardeners. Not only are they hardy, but their flowers are large and vivid, and scented varieties give off pleasant aromas. You can enjoy your geraniums for just one season and buy new plants every year, or try your hand at wintering-over whole plants or propagating new ones from cuttings.
Plant geraniums in the spring after the danger of frost has passed. They'll do best in slightly acidic soil (pH about 6.5) that's well-drained and aerated. If you have heavy clay soil, add some peat moss, compost or partly-rotted manure to the soil every year. Geraniums will produce the most flowers if planted in full sunlight, although they will grow in partial shade.
Place the plants in the ground no deeper than they were in the pot. A bit less depth is even better, since it will help to prevent the roots from rotting. Tamp the soil down around the roots and water the plant. Add a 5-10-5 fertiliser according to the manufacturer's directions and water again. Wash off any fertiliser on the leaves, as it will burn the plant.
Pinch off dead flower stalks regularly, since they can contribute to botrytis. Botrytis is a blight that shows up as greyish areas or black spots on leaves, shoots and flowers. If you find blight, remove the affected areas and dispose of them. Do not remove blighted areas when the plants are wet, since this spreads the spores more easily. Plant the geraniums far enough apart to prevent them from touching and possibly spreading the blight. Weed your plants regularly.
Geraniums are resistant to drought and don't require a lot of water. Take care not to overwater your plants. When you do water, do it early in the day and water only the roots. Wetting the leaves can make them more susceptible to infection with spores from other plants.
Wintering-Over and Propagation
Dig up geraniums in late summer, cut them back to half their height and put them in pots. Keep them in a sunny window indoors and replant in the spring. Some gardeners remove the dirt from the roots and hang the plants in the basement during the dormant season, but this requires about 70 to 80 per cent humidity and temperatures between 1.66 to 7.22 degrees C.
Propagate your geraniums by taking cuttings in late summer, before any danger of frost. Cut the tips off shoots in three- to five-inch lengths and remove all the leaves. Dip the end of each cutting in a rooting hormone to promote growth, and plant the cuttings in a shallow container filled with planting medium, at a depth of about 1 1/2 inches. You can buy prepared medium or use vermiculite, sand or perlite, or mix all three together. The medium should be moist rather than wet. Give the cuttings enough room for air to circulate around them. Put a plastic bag over the container to help preserve moisture. Open the bag occasionally to prevent overheating, and check the moisture of the planting medium. Add water when necessary, usually about every two weeks. Put the container in a spot that receives indirect sunlight. Test for rooting by gently pulling on the cuttings. If you feel resistance, the roots have taken hold and you can plant the cuttings in potting soil. Plant them at the same depth as the medium and gradually increase their exposure to direct sunlight. Water as needed. When new growth appears, begin adding fertiliser.