Great Willowherb thrives in consistently moist soil. Water regularly, especially during dry spells, ensuring the soil never completely dries out.

Aim for moist but not waterlogged conditions, mimicking its natural preference for damp environments. Reduce watering slightly in cooler months.

Deadhead spent flowers to encourage further blooming and prevent excessive self-seeding. In autumn, cut back the plant to the ground to maintain a tidy appearance and remove any diseased or damaged stems.

This also helps the plant overwinter effectively.

Epilobium hirsutum is easily propagated from seed, which can be sown in autumn or spring. It also readily spreads via rhizomes.

Division of established clumps in spring is another effective method for increasing the plant population.

As Great Willowherb is a vigorous perennial that often spreads through rhizomes, it may require division rather than repotting. If grown in a container, repot every 2-3 years in spring into a slightly larger pot with fresh, well-draining soil.