Greater Water-parsnip thrives in consistently moist to waterlogged conditions. It is an aquatic or semi-aquatic plant, so its roots should be submerged or in very wet soil.

Regular watering is essential, especially during warmer months, to prevent the substrate from drying out. Aim for standing water or soil that remains saturated.

Pruning is primarily for aesthetic control and to manage its spread. Remove dead or yellowing foliage as it appears throughout the growing season.

In autumn, cut back the plant to the water surface or ground level to prevent decay and improve overwintering conditions. It can be divided in spring if it becomes too dense.

Sium latifolium is easily propagated by division of established clumps in spring before new growth fully emerges. It also readily self-seeds in suitable conditions.

Seeds can be collected in late summer or autumn and sown in moist soil or shallow water. Stem cuttings can also be taken in summer.

Repotting is generally only necessary if the plant is outgrowing its container or needs dividing. This is best done in early spring before active growth begins.

If grown in a container, use a large, sturdy pot designed for aquatic plants. Ensure the pot has drainage holes if planting in a pond's edge.