Flowers and perennials

Start with a map of light and moisture. Neighbours grow together more easily when similar care suits them. Then compare mature width, height and flowering periods. Hostas in shade and lavender in a sunny, well-drained position can belong to the same garden without needing identical watering in one tightly packed group.

Assess whether the centre has weakened, flowering has declined or neighbours are being crowded. Then check whether that species tolerates division and which timing suits it. Not all perennials need frequent division. Each division needs viable roots, a suitable position and moisture checks until establishment.

Not necessarily. Separate clearly diseased remains; healthy ornamental stems may be selectively left until a suitable time. Consider species hardiness, site moisture and new growth in spring. Do not leave a dense wet mass at sensitive plant bases or apply one cleanup method to the whole bed.