This is a good month to be sowing new lawns. It may be cool still, but it is warm enough for grass seed to germinate and to be establishing before the hot weather comes. Lawns sown last autumn will have their roots down by now and will need no watering. Newly sown lawns may need watering if there are early-season dry spells.
April is the time to deal with moss in lawns. Apply chemicals according to the makers instructions and then rake out the dead moss. The grass is beginning to grow now, and should soon thicken and spread into the gaps left by the moss.
Pruning and Training
Summer-flowering heathers can be clipped over just as they start to grow again at the tips. Shear off the old flowered parts of the stems, to encourage lower side shoots to fill out and keep the plants dense and even.
April is a good time to undertake the major rejuvenative pruning of yew hedges which have become too fat or tall. Cut everything right back to the trunks on one side, and feed and water well during the year. Cut the top back next year, and the other side the year after.
Start nipping out with finger and thumb the principal leaders of shrubs you wish to keep dense, such as rosemary, sages, and cistus. Nipping now makes for a fuller bush in later years.
Sow hardy annuals like cornflowers, nasturtiums and calendulas where they are intended to flower.
The more prized daffodils can be dead-headed if you have the patience, to build up the bulbs for next year.
Plant gladioli in good rich soil 15 cm deep.
Any tender plants bought now for summer pots and containers must be left outside on mild days only, to harden them off, and brought under glass or indoors if frost threatens.
If you grow roses which are prone to fungal diseases, now is the time to start a programme of spraying with fungicide. Don't wait for the symptoms to appear.
Time to get potatoes and onion sets in.
Sow peas, broad beans, cauliflowers, brussels sprouts, onions, turnips, beetroot, parsnips and leeks.