Garden Notes for April 2021.
I know that all the gardener advice is to cover over a patch of ground to warm up the soil and I should have done it a lot more than I have in the past. This season I did remember and have used a cheap polythene cloche that extends for about 10 metres. You can tell when the soil is warm enough when all the weeds start sprouting under it. As well as warming the soil it has also stopped it getting sodden with rain. The result is that I can really start salad crops like lettuce, radish and carrots this month, after getting rid of the weeds under the cloche.
Clematis varieties 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.
April is the time to plant late flowering herbaceous plants 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 as the weather warms up towards the end of the month. 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.