Water Ageratum fastigiatum regularly, keeping the soil consistently moist but not waterlogged. Allow the top inch of soil to dry slightly between waterings, especially during hot, dry periods.

Reduce watering in cooler months to prevent root rot.

Pinch back young plants to encourage bushier growth. Deadhead spent flowers regularly to promote continuous blooming and prevent the plant from going to seed.

Light pruning can be done to shape the plant and maintain a tidy appearance.

Ageratum fastigiatum is easily propagated from seed sown indoors in early spring or directly outdoors after the last frost. Cuttings can also be taken from mature plants in late spring or early summer and rooted in moist potting mix.

Repot young plants as needed when they become root-bound, typically every spring. Choose a pot one size larger with good drainage.

Mature plants generally do not require frequent repotting and can thrive in their containers for several seasons.