Growing Spirea in a pot

Spiraea japonica has moderate water needs. Once established, it tolerates short dry spells but performs best with consistent moisture during spring and summer, especially in sandy soils. Water deeply every week to ten days in prolonged dry weather; reduce frequency in autumn and winter when rainfall is usually adequate. Avoid waterlogging, which can lead to root problems on heavy clay. Feed in March or April as growth resumes. Scatter a general-purpose granular fertiliser such as Growmore or blood, fish, and bone around the base at roughly 70 g per square metre, then water in or lightly fork into the soil surface. A second, lighter feed in late April can be beneficial on poor soils but isn't necessary on fertile ground. Over-feeding encourages soft, leafy growth at the expense of flowers. Mulch annually in spring with a 5 cm layer of garden compost, well-rotted manure, or bark to suppress weeds, retain moisture, and gradually improve soil structure. Keep mulch clear of the stems. Spiraea japonica is generally trouble-free. Aphids occasionally cluster on soft new growth in late spring; a strong jet of water or an insecticidal soap usually resolves the problem. Powdery mildew can appear as a white coating on leaves in dry summers, particularly in sheltered spots with poor air circulation; improve spacing and water at the base rather than overhead. This shrub is fully hardy across temperate Europe and requires no winter protection.