Flowers
Put supports in place before plants are too tall, or for those- like peonies- that produce heavy blooms. Supporting now allows plants to grow naturally preventing them looking bunched and allows more ventilation.

Harden off plants grown from seed and cuttings by leaving them out for increasing lengths of time building up to overnight exposure.

Divide clumps of herbaceous perennials making sure that the transplanted divisions have roots and shoots and are adequately watered. Cutting back clumps of spring-flowering perennials encourages attractive new growth.

Train sweet peas by tying to supports to encourage them to climb and give a good display. Tubs can be planted up with summer bedding plants in milder areas. In cold areas it is better to wait until all risks of frost have passed.
Liquid feed plants in containers every two to four weeks.

If you want to grow your own spring bedding plants for next year(wallflowers, pansies) seeds need to be sown between now and July in order to flower for the spring.

As spring bulbs fade deadhead and apply a liquid fertilizer to encourage a good flowering for next year. Allow foliage to die down naturally rather than tying in knots. Only remove when it has turned brown and floppy. Lift and divide over crowded clumps of spring bulbs.

Vegetables
Continue with successional sowing of salad crops to ensure an even supply over the season.
Sow French and runner beans, squash, cucumbers and pumpkin seeds directly into prepared beds outside. Be alert to late frosts. Runner beans benefit from well-prepared ground with lots of well-rotted manure. They need sturdy supports for the plants to climb up.
 
Sow cauliflowers and purple sprouting broccoli for harvesting for next winter. Try sowing unusual vegetables such as kohl rabi.
Transplant Brussels sprouts after early or mid-spring sowing. Gaps in between can be used for short-term ‘catch crops’ like radishes.
Earth up potatoes when shoots are 23cm high.
Leeks can be sown outside or indoors. Transplant when they reach 10cm in height.
Start to remove side shoots from cordon tomatoes.