Water Black Horehound regularly, allowing the soil to dry slightly between waterings. It prefers consistently moist soil but can tolerate short periods of drought once established.

Avoid overwatering, which can lead to root rot. Ensure good drainage to prevent waterlogging.

Prune Black Horehound in early spring to shape the plant and remove any winter damage. Deadhead spent flowers to encourage further blooming and prevent self-seeding if unwanted.

Pruning also helps maintain a more compact and bushy habit.

Propagate Black Horehound from seed sown in spring or autumn. It can also be propagated by softwood cuttings taken in late spring or semi-hardwood cuttings in summer.

Division of established clumps in spring is another effective method.

Repot container-grown Black Horehound every 2-3 years, or when the plant becomes root-bound. Spring is the ideal time for repotting.

Use a well-draining potting mix and choose a pot slightly larger than the current one to accommodate root growth.