Set out plants about 18 inches apart in a sunny location, making certain not to plant the strong, clumpy root too deeply. The soil should be moisture-retentive, but need not be especially fertile. In areas north of zone 7, plant in large containers and bring in over the winter.
Keep plants well-watered during the growing season. Agapanthus will bloom best if pot-bound, but will also bloom prolifically when planted outdoors, as long as they are not moved. Occasionally, however, severe overcrowding will lead to reduced flowering. If that happens, divide the plants as necessary; flowers will again bloom profusely after a couple of years. In the North, containers should be brought in to a frost-free environment for the winter before the fall frost begin.
Water should be gradually withheld to encourage the plant to go into a dormant state. Low light and cool temperatures should be maintained during the winter. To induce growth the following spring, put agapanthus in good sunlight and increase watering as new growth increases. Begin fertilizing when this growth has reached 6 to 9 inches and continue regularly through the growing season. Zones 6-10.
Zones 6 to 10