The Right Place
Light - Geraniums like full sun, at least six hours' worth, and afternoon dappled shade in the hotter regions. Newer varieties can handle heat but can be knocked out by prolonged high heat and humidity. Most geraniums grow best in part shade (preferably afternoon shade) in the hot climates. Seedlings need strong light to encourage dense, stocky plants.
Soil - Geraniums prefer a light, moist, well-drained soil high in organic matter. While they tolerate a variety of soils, they seem to grow best in slightly acid soil (pH 5.5 to 6.0).
Starting From Seed - Many varieties of Geranium can be started from seed. For details about starting seeds indoors and out, see Starting Plants From Seed and check out Seed Starting Equipment and Supplies in Yardener’s Tool Shed.
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Planting Seedlings -
Plant seedlings or young plants purchased from a nursery outside only after all danger of frost is past. Choose an overcast day or late afternoon to plant, so the geraniums will not be stressed by the sun. Loosen the soil in the planting area with a shovel, spade or trowel down about 10 inches, removing sticks, stones and other debris, then smooth it. Dig a hole for each young geranium slightly larger than the container it is in. Unpot each plant by gently rapping the base of the container with the trowel to loosen the soilball. Tip the plant out, taking care to preserve any roots that protrude from the bottom of the pot. Set each plant in its hole at the same depth it was in the pot, firm the soil around the stem and water well. Allow at least 15 to 18 inches between plants, 12 inches for groundcover situations. For planting tools see Hand Tools For Digging and Planting in Yardener’s Tool Shed.
In Containers - When potting geraniums, be sure the container has drainage holes. Fill it with commercial soilless mix which is sterile. If it is a soilless mix either add granular slow-acting fertilizer to it at this time, or plan to fertilize with a liquid product periodically over the season when you water. See Growing Plants In Containers and Containers For Plants in Yardener’s Tool Shed.
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Propagating
Rooting stem cuttings is the most economical way to build up a supply of geraniums for outdoor use next spring. Cut pieces of stem from healthy plants about 4 inches down from their tips. Use a sharp knife or razor blade rather than pruning shears to avoid pinching or crushing the stems. Be sure there are at least 3 leaves on the piece of stem. While stem cuttings will root in a glass of water, for best results use a sterile rooting medium such as damp vermiculite or coarse sand.
Pull off any leaves near the cut end, and dip the end in rooting hormone (optional) which is available in any garden center or nursery. Stick the cuttings into flats or pots of the sterile medium and water them immediately. Keep them out of direct sunlight and fairly dry, as they develop roots over the next 2 or 3 weeks. Then plant the rooted cuttings in 2 1/2 inch pots until it is safely past frost. Young new plants from cuttings started in the fall will grow in a sunny window, but even better under fluorescent lights that are kept only 6 inches above the tops of the growing plants. They will begin showing their first blooms in January. By spring they will develop into sturdy plants for the garden beds, borders and containers. For information about propagation equipment go to the Plant Propagation Equipment section of Yardener’s Tool Shed.