The Gardening Year for Bulbous Plants
Spring
In early to mid-spring, plant summer-flowering bulbs in prepared ground or in containers indoors or outdoors. Snowdrops may be planted 'in the green' (still in leaf).
Water and feed established bulbs and deadhead spent flowers. Any tall plants grown in pots should be supported with canes and ties. Re-pot or top-dress bulbs in containers.
In late spring, cut the grass in areas where naturalised bulbs grow; wait until at least 5 weeks after the plant has stopped flowering or until the foliage has turned yellow. Lift and divide clumps of bluebells after flowering, whilst you can still see the foliage.
If propagating plants, collect the ripe seed of early-flowering bulbs, or take basal stem cuttings of dahlias and begonias. Dahlia tubers may be lifted and divided.
Summer
Lift early-flowering bulbs that need to be moved and heel them in elsewhere in the garden to allow their leaves to die down. Any over-crowded clumps should be divided at this point.
Pot-grown bulbs may be planted in the open garden once their foliage has died down.
In mid to late-summer, plant autumn-flowering bulbs, such as autumn crocus (Colchicum) and autumn daffodil (Sternbergia). Autumn-flowering bulbs are dormant in summer, so bulbs already in place may be lifted, divided and replanted singly.
Water, and if necessary, feed, summer-flowering bulbs grown under cover or in containers. Deadhead any spent flowers, unless the seed is needed for propagation; these should be collected in late summer. Bulbils and bulblets may be removed from dormant bulbs and potted up. Lilies and other bulbs may be propagated by scaling or twin-scaling in late summer.
Autumn
In early autumn, plant spring-flowering bulbs or seeds in prepared ground or in containers. Hyacinths and other bulbs may be potted up at this point for forcing and kept in a cold garage or cold frame.
Water autumn-flowering bulbs grown under cover or in containers. Forced bulbs and resting bulbs should also be watered. Once the foliage of summer-flowering plants such as dahlias and tuberous begonias has died down, lift the roots and store in a cool, dark place indoors.
Winter
In mid-winter, prepare the soil for summer-flowering bulbs to be planted in spring. Bring potted bulbs such as hyacinths and narcissi from their cool storage into slightly warmer conditions indoors, with maximum light to start them into growth. Water lightly, then more regularly once they start to produce new leaves and flower buds.
Bulbs such as snowdrops and winter aconites prefer to be divided 'in the green' in late winter when they are in full leaf, or even when they are in flower. Split them into smaller clumps and re-plant.