Water newly planted Buddleja davidii regularly to establish a strong root system. Once established, it is quite drought-tolerant and requires less frequent watering.

Provide deep watering during prolonged dry spells, especially in hot climates, to encourage vigorous growth and abundant flowering. Avoid waterlogging, as this can lead to root rot.

Prune Buddleja davidii hard in late winter or early spring, before new growth begins. Cut back stems to about 30-60 cm from the ground to encourage strong new shoots and abundant flowers, as it blooms on new wood.

Deadhead spent flowers throughout the summer to promote continuous blooming and prevent self-seeding, which can contribute to its invasive nature.

Buddleja davidii is easily propagated from semi-hardwood cuttings taken in summer or hardwood cuttings in autumn/winter. Cuttings should be about 10-15 cm long, with leaves removed from the bottom half.

Dip the cut end in rooting hormone and plant in a well-draining potting mix. Keep moist and warm until roots develop.

As a large outdoor shrub, Buddleja davidii is typically planted directly in the ground and does not require repotting. If grown in a container, choose a large pot to accommodate its rapid growth.

Repotting would involve moving it to an even larger container or refreshing the soil every few years, though ground planting is generally preferred for mature specimens.