Water regularly, especially during establishment and dry periods, to maintain consistent soil moisture. Avoid waterlogged conditions, which can lead to root rot.

Once established, Narrow-leaved Ash is relatively drought-tolerant, but supplemental watering during prolonged dry spells will promote healthier growth and vigor.

Prune for shape, structure, and to remove dead, damaged, or crossing branches. The best time for major pruning is during the dormant season (late autumn to late winter) when the tree's structure is visible.

Minor pruning to remove suckers or improve form can be done at other times, but avoid heavy pruning in spring.

Propagation is typically done from seeds, which require a period of cold stratification to overcome dormancy. Sow seeds in autumn in a sheltered spot or in spring after stratification.

Grafting onto a suitable rootstock can also be used for specific cultivars, ensuring better establishment and desired characteristics.

Repotting is generally not applicable to mature trees grown in the ground. For young trees or container specimens, repot in late winter or early spring before bud break.

Choose a pot with good drainage and use well-draining soil. Ensure the root ball is not overly compacted before placing it in the new container.