TREES AND SHRUBS
Deadhead rhododendrons and azaleas to encourage the formation of next year’s blooms.
Plant out shrubs that are tender when young, such as choisya, hydrangea and fuchsia.
Keep newly planted trees and shrubs moist at the roots during dry periods. Spray foliage with water from time to time.
When the soil is moist, spread a mulch of pulverised bark, compost or well-rotted manure.
Lightly dress all trees and shrubs with a high nitrogen general fertiliser.

ROSES
Deal with any sign of aphid infestation or disease immediately; if you are using a systematic insecticide or fungicide, spray in the early morning or late evening.

HERBACEOUS PERENNIALS
Remove growing tips of tall perennials such as asters and solidago, and thin out weak shoots from the centre of overcrowded plants to promote sturdy growth and better flowers.
Mulch all plants with well-rotted manure or garden compost.

ALPINES
Trim back spreading plants, such as aubrietia and arabis, 2-3in from the base when they have finished flowering.

WATER AND BOG PLANTS
Divide and replant any marginal plants – such as Primula japonica – that have spread beyond their allotted spaces.
Thin overgrown clumps of water lilies and remove some of the larger leaves.
If necessary, water the bog garden to keep it moist during dry spells.

BULBS, CORMS AND TUBERS
Plant half-hardy bulbs such as crinum in sheltered positions.
Plant dahlia tubers in well-prepared ground that has been enriched beforehand with well-rotted manure or garden compost.
Plant Amaryllis belladonna as soon as the bulbs become available.
If you are going to lift bulbous plants to make way for summer bedding, heel them into a spare piece of ground until the foliage has died back. The bulbs can then be lifted, dried and stored in a cool, dry place.

ANNUALS AND BIENNIALS
Complete sowing hardy annuals outside as soon as possible. Sow biennials in a seedbed outdoors, ready for next spring.
Plant out half-hardy annuals when fear of frost has passed. In the south of Britain, this is usually around mid-May.
Liquid feed any young plants still in boxes before planting out in the garden.

LAWNS
Apply weedkiller – which is more effective when weeds are growing strongly – or cut out weeds with a knife.
Mow the grass regularly. Trim the edges of the lawn after every cut.

GENERAL MAINTENANCE
Remove suckers – shoots rising from ground level, directly from the roots – from roses, lilacs and other shrubs.
Water plants copiously – at least 1 gallon per square yard at each watering – during dry spells over this critical growth period.
Protect plants from slugs, especially when weather is warm and humid.
How frequently to remove weeds while they are still young.

Next:
Early Summer