April Grow your own

Jobs for April

Chit and plant out second early potatoes in the first half of the month and maincrop potatoes in the second half. Potatoes can be planted in deep drills or in individual planting holes, with 5cm (2in) of soil mounded over the top. Alternatively, plant them through slits in black polythene mulch, or grow them in thick plastic bags (old potting compost bags are perfect).

If you live in a very mild area, and got off to an early start with your potatoes last month, they may be ready for earthing up to exclude light and prevent the tubers going green. Start earthing up as the shoots grow, covering them entirely if frosts threaten, and finishing when the earthed up ridge is about 25cm (10in) high. Potatoes grown under black polythene do not need earthing up, as the polythene excludes enough light. If frost threatens, then cover the shoots with horticultural fleece to protect them.

Sow beetroot, carrots, Swiss chard, summer cauliflower, kohl rabi, lettuce, leeks, radish, turnip, spring and pickling onions, peas and perpetual spinach in well-prepared soil.

Try sowing some unusual vegetables such as salsify, Hamburg parsley, or scorzonera, both root vegetables favoured by the Victorians, and still eaten a lot on the Continent.

Broad beans grown in pots can now be transplanted into the garden.

Plant shallots, garlic and onion sets. Plant Jerusalem artichoke tubers.

Plant asparagus crowns. A deep, friable, well-drained soil with plenty of organic matter incorporated is ideal.

Pea plants should be supported with sticks, twigs, green support mesh, or wire netting from the garden centre.

In the second half of the month (wait until early May in cold areas) you can sow marrows, courgettes, pumpkins and squash in a heated glasshouse at a germination temperature of 16°C (61°F).

In very mild areas you may be able to sow dwarf French beans and sweet corn outside under cloches or fleece, but in cooler areas it is best to wait until May.

Thin out rows of seedlings as soon as they are large enough to be handled.

Sow a seedbed of brassicas to provide transplants of sprouting broccoli, cauliflowers and cabbages that will be ready for planting out to their final position in June or July, and for harvesting in autumn/winter. It is rather late for sowing Brussels sprouts, but you can still buy young plants from garden centres.

Fleece and polythene can be used to protect early outdoor sowings. Many vegetables can bolt if sown outside too early without protection (beetroot being an example). A greenhouse or conservatory is useful in all but the very mildest areas with the lightest soils, to start seeds off, hardening off and transplanting the young plants into the vegetable garden later in the spring.

Sweet peppers, tomatoes, cucumbers, aubergines, celery, salads and globe artichokes can all be sown in a frost-free greenhouse. Artichokes and celery can be transplanted outside later in the spring. Tomatoes germinate best at 22°C (72°F), and can either remain in the greenhouse or go outside from early summer onwards. Peppers, cucumbers and aubergines do best kept under cover throughout their life.

Pot up tomato seedlings when they develop true leaves above the more rounded seed leaves. After growing on in small pots, they can be planted into larger pots or growing-bags.

Continue to force witloof chicory and seakale. Dig up selected chicory roots, pot them up, and position them in a dark warm place (10-13°C; 50-55°F), with an upturned pot over them. The tasty chicons will appear in three to six weeks. Seakale is best forced outside at seasonal temperatures, with an upturned pot or cardboard box/tube over the top to exclude the light.

Plant out onions sown from seed earlier in the spring. Don’t use ground used for onions in the last three years to prevent disease problems.

Finish harvesting Jerusalem artichokes, leeks, winter salads, chicory, kale and sprouting broccoli. Start to harvest spring onions, radishes, spring cauliflowers, spring cabbages and un-forced rhubarb.

Control weeds by hoeing between rows during dry weather.

You could prepare your runner bean supports and trenches for sowing (in May) or planting out (in June). This will save you time later.

Material courtesy of www.rhs.org.uk