Garden Notes for April 2020.
Clematis are popular. They are members of the Ranunculae, which are named after ‘Rana’ (the frog) and demand a cool moist root run. When planting remember that they need shade at the base so it is a good idea to put a piece of stone or paving over the top after you have planted them out.
Plant late flowering herbaceous plants in April, such as kniphofias and michelmas daisies (Aster novi-belgii). Old clumps of taller rudbekias, helianthuses, monardas and heleniums will benefit from being split up in April since this will revitalise them, especially if they have been producing smaller flowers and losing their lower leaves in the previous season.
Plant onion sets and keep up a succession of salad crop sowings. April is the time to sow late summer cauliflower. If frost is forecast, cover up any potato foliage that might be showing. Make sowings of winter cabbage, purple-sprouting and spring-heading broccoli.
Don’t forget herbs. You can sow dill, fennel, hyssop, marjoram, rue and thyme. Parsley should be sown, allow time for it to germinate. Old fashioned gardeners used to keep a little bit of seed in a waistcoat pocket with a hole so it fell out as they gardened! (So they tell me).
If you have sweet peas they should be planted out now. If you are going to try and grow the larger specimens as cordons, start restricting growth by removing all tendrils and side shoots and remember to support them otherwise the slugs and snails will have a feast.
Towards the end of the month, if we have had dry weather, start to thin out salad crops like carrot. One tip is to water the row the night before so that it is easier to pull the roots out the next day.
Camellias will benefit from a top dressing of leaf mould. Remember to prune early flowering shrubs like berberis, forsythia, and spiraea immediately after flowering.
Do remember that early morning frosts are a real danger all through April and May, it is not until June, (and even then it can be a bit dicey for the first week!) that it is safe to put out any vulnerable plants – unless you can protect them at night.