Hardy annuals can be sown in pots or modules to provide colour in the garden. Annual grasses can be fun to try too: Briza maxima, Lagurus ovatus and Hordeum jubatum are examples. In mild areas with light soil, we can sow directly outside by marking out irregularly-shaped seedbeds and broadcasting 'drifts' of different seed to give a more natural look.
Modular trays are useful for sowing half-hardy summer bedding plants such as marigolds (Tagetes), Lobelia and Petunia. Label each seed tray. You will need to sow them under cover, or in a heated propagator, at the correct temperature – putting them outside only when the weather is reliably warm day and night.
Sweet peas can be sown outside in April. Plant out autumn-sown sweet peas that have been raised in pots, and prepare your wigwam supports for them to climb, using a light twine to tie the plants in.
If you started sowing early in March, or even February, you may have modules of young hardy annuals ready for planting out.
Towards the end of April, in mild areas, you may be able to plant-up hanging baskets for summer. Use slow-release fertiliser and water-retaining gel.
When space becomes available in the greenhouse, pot up cuttings of tender perennials taken last summer and at the beginning of this year. You can bulk up plant numbers by taking more cuttings from the largest of the new plants.
Plant summer-flowering bulbs, if not done already. Prepare the soil first, to ensure drainage is sufficient to prevent the bulbs rotting. Anemone coronaria tubers, for instance, need particularly well-drained soils.
Top 10 jobs this month
1 Keep weeds under control; 2 Protect fruit blossom from late frosts; 3 Tie in climbing and rambling roses; 4 Sow hardy annuals, herbs and wild flower seed outdoors; 5 Start to feed citrus plants; 6 Increase the water given to houseplants; 7 Feed hungry shrubs and roses; 8 Sow new lawns or repair bare patches; 9 Prune fig trees; 10 Divide bamboos and waterlilies.
The Royal Horticultural Society wants to enrich everyone's life through plants, and make the UK a greener and more beautiful place. Members benefit from free, year-round, gardening advice. www.rhs.org.uk
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