Pinch out the shoot tips of spindly plants to encourage branching. Ideal growing temperatures for geraniums are 70 to 75 degrees during the day and 60 to 65 degrees at night. Thoroughly water geraniums when the soil surface is dry to the touch. Fertilize weekly with a one-quarter strength houseplant fertilizer. Harden or condition the plants outdoors for seven to ten days before planting into the garden.
Plant geraniums outdoors when the danger of frost has passed.
Geraniums can be planted outdoors in early May in southern Iowa, mid-May in central and northern portions of the state. Iowa State University , Ames, Iowa. This information subject to a usage policy .