Prune agapanthus regularly each spring to remove branches that have been killed or damaged by winter weather. During the growing season, prune it as needed to remove dead flowers, leaves and disruptive growths. Use sharp shears capable of making a clean cut. Sterilize the pruning shears with either rubbing alcohol or bleach to minimize the spread of disease.
Remove frost damage in the spring
After the final frost date, identify and remove branches damaged by the winter frost. Cut branches on a diagonal.
Deadhead spent flowers
After flowers lose their petals, deadhead them to prevent them from seeding and drawing energy away from other parts of the plant. Deadhead the flowers by cutting as close to the base as possible while removing the dying flower completely.
Search for and remove diseased branches
Throughout the growing season, stay alert for diseased leaves or branches that threaten the health of the overall plant. Prune these away immediately and dispose of them securely.
Prune flowering stems for winter
After the flowering season and before the first frost, prune down flowering stems to make room for new growth in the following year.
Divide the plant
Every few years, divide the agapanthus to prevent overgrowth. Cut down the plant by half and either replant or dispose of the removed portion.