Garden Jobs to do Article – April

Vegetables

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 of soil mounded over the top. Alternatively, plant them through slits in black polythene mulch.

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 entiriely if frosts threaten, and finishing when the earthed up ridge is about 25cm 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.

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

Plant shallots, garlic and onion sets.

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 the garden centre.

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.

If you have still been forcing rhubarb plants under forcing jars, take the last crop of pale stems, feed with general fertiliser, and leave them uncovered to grow without cropping for the rest of the year.

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

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.

Flowers

Put supports in place for perennials before they get too large to manage this easily. It is best to get the supports in early, so that the plants grow up through them, covering them discreetly. Adding rigid supports afterwards usually looks unattractive and results in bunched stems lacking sufficient ventilation. Criss-crossing strings from hidden or decorative posts work well, allowing stems to grow up in the gaps between strings. 

Remove faded daffodil and tulip flowers, nipping off the heads and seed pod at the same time.

Deadhead pansies, primulas and other spring bedding plants. Pansies will carry on into the spring and even to early summer, if attended to frequently.

Remove tired winter bedding and plants that did not survive the winter.

Check that self-seeded forget-me-not isn’t smothering other border plants. Pull out plants if necessary.

Divide clumps of herbaceous perennials that you want to propagate, those that have become too large for their allotted space, and those that are flowering poorly or have lost their shape. Bamboos and clumps of bulbs or rhizomes can be divided in the same way. Just make sure that the transplanted divisions have roots, shoots, and are given adequate water to settle into their new positions.

You can still plant herbaceous perennials such as Geranium, Astrantia and Oriental poppies. Check that the plants you buy have strong, green shoots and plant them into well-prepared soil.

Hardy annuals can be sown in pots or modules to provide colour in the garden. They are inexpensive and can also provide fun activity for children. Suitable examples include Limnanthes, Nemophila, Lobularia and Consolida. There are annual grasses that can be fun to try too: Briza maxima, Lagurus ovatus and Hordeum jubatum are suitable examples. In mild areas with light soil, you can sow directly outside. Marking out irregularly shaped seedbeds and broadcasting ‘drifts’ of different seed gives 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 plant them under cover, or in a heated propagator, at the appropriate temperature, only putting them outside when the weather is reliably warm day and night.

If you started sowing early, in March or even February, you may have modules of young hardy annuals now ready for planting out.

When space becomes available in the greenhouse, pot up cuttings of tender perennials taken last summer and at the beginning of this year. Bulk up plant numbers by taking more cuttings from the largest of the new plants.

Sweet peas can be sown outside this month. Fleece covering can be used to raise the temperature and encourage seedling growth in cooler areas, or they can be started off in a cold frame. Some types may need chitting (nicking of the seed coat), and/or soaking, in order to germinate.

Prune penstemons and other slightly tender plants such as Teucrium and lavender. Make the cuts just above fresh, new shoots.

Apply a general-purpose fertiliser to borders and beds. Take care not to damage emerging shoots, or to burn them with fertiliser.

Check whether containers need watering. Even at this time of year, they can dry out. Pots that are sheltered by eaves or balconies can miss out on any rainfall. If in doubt, check the compost at a hand’s depth to see if it feels dry. Aim to keep pots moist, not wet, and don’t let them dry out.

Pots and tubs benefit from topping up with fresh compost. Old compost can be removed and replaced with new to a depth of 5cm (2in) if there is not much room for topping up.

Pot on plants showing signs of being pot-bound. You can tip out the rootballs of unhappy looking containerised specimens, to see if they are indeed pot-bound or if they are suffering from some other problem.

Hoe borders to prevent annual and perennial weeds from spreading and seeding themselves.

Perennials that are showing new shoots from the crown can be propagated via basal stem cuttings. Shoots 8-10cm (3-4in) high are cut from the parent plant with a sharp knife. Sometimes a piece of root can be taken with the cutting (which speeds establishment), but stems can be cut without root, and then dipped in hormone rooting powder before striking into growing medium, as for softwood cuttings.

Plan a continuous crop of cut flowers for this summer. Perennials such as delphiniums and annuals can be grown to produce a useful and beautiful display.

Towards the end of the month, in mild areas, you may be able to plant up your hanging baskets for the summer.

Some perennials benefit from having their flowering shoots thinned out. Although this results in fewer blooms, they are larger and of better quality, particularly useful for growing and showing enthusiasts. Delphiniums, lupins and Phlox all benefit from this process.

When gardening on wet soils work from a long plank of wood rather than treading on the bed to avoid compacting the soil.

Trees & Shrubs

Mulch rose and shrub beds with a 5-7.5cm (2-3in) layer of organic matter. This will help retain moisture during dry spells, reduce weed build-up and over time improve soil structure. Pay particular attention to mulching around rhododendrons, azaleas and camellias as flowering is impaired if they are allowed to dry out during late summer.

Tie in climbing and rambling roses as near to horizontal as possible. This will restrict sap flow causing more sideshoots to grow along the length of stem. Therefore more flowers will be produced.

In colder northern regions, and early in the month, you can still move and plant evergreen trees and shrubs, provided the soil is not waterlogged. They are best moved or planted once actively growing and when there is less risk of cold. In warmer regions, it is best to wait until the autumn, as the weather will soon turn warm and dry, and the plants will have trouble establishing.

Feed trees, shrubs and hedges with a balanced fertiliser (such as Growmore or blood, fish and bone), sprinkling it over the root area before hoeing into the soil surface. This will particularly benefit young, weak, damaged or heavily pruned plants.

If not completed last month or before, winter-stemmed shrubs such as Salix and Cornus can still be cut back at the beginning of the month. Prune back hard all the previous year's growth to within 1-2cm (0.5-0.75in) of the framework.

Other shrubs that are routinely stooled (cut back hard) in spring, to keep their larger or more brightly coloured juvenile foliage (such as Cotinus and Sambucus), can be cut back this month. You can leave a couple of branches un-pruned if you are reluctant to lose all the height gained last year.

Delay pruning spring-flowering shrubs such as Forsythia and Chaenomeles until after they have finished flowering, otherwise this year's display will be lost.

Prune evergreen shrubs such as Choisya ternata, Prunus laurocerasus, and evergreen Ceanothus.

Remove any frost damaged shoots from evergreens damaged by earlier cold weather.

Lightly cut back lavenders to prevent them getting too leggy and woody.

Loosen any tree ties that are digging into the bark, or could do so soon as the trunk girth expands.

Take cuttings of your favourite conifers.

Twining climbers (such as honeysuckle and Clematis) need regular tying in and twining around their supports.

Check hardwood cuttings taken last year. They may need planting out or potting on.

Fruit

Although blackcurrants, blackberries and hybrid berries should have already been fed in January or February, they benefit from a further feed (30g per sq m) with a high nitrogen fertiliser such as sulphate of ammonia or nitrochalk.

Before the buds break on wall-trained figs, look for any badly placed shoots that are growing into or away from the fence or wall and remove them. Tie in the remaining shoots.

Start pruning trained fruit tree forms (such as espaliers, fans and cordons). These forms are pruned when in active growth, to keep down their size and to encourage fruit bud formation.

It is now safe to prune plum and cherry trees, which are vulnerable to the disease silver leaf if pruned in autumn or winter.

Control weeds. Hoe shallowly around fruit trees and bushes during dry weather.

You can still plant container grown fruit trees and bushes, as long as the ground is not too wet or frozen. Incorporate lots of well-rotted organic matter into the ground before digging the planting hole or trench. Take care to water well in dry weather, as the plants will not have much time to establish before the hot, dry season begins.

Place cloches or fleece over outdoor strawberry plants for an early crop. Make sure to remove the fleece or cloche during the warmest part of the day, to allow pollinating insects to enter. High potassium feeds (such as tomato fertiliser) will also help to encourage flowers and fruit.

Lawns & Meadows

Mow lawns when necessary - whenever the grass is growing - the aim is to maintain a constant height throughout the year.

Add the clippings to the compost heap in thin layers (too much grass all at once is likely to be very wet and poorly aerated, resulting in smelly slime rather than compost).

Cut the lawn edges with a half-moon edging iron to ensure they are neat and well shaped.

Use a half-moon edging iron or spade to create a 7.5cm (3in) ‘gutter’ around the lawn edge. This will prevent grass creeping from the lawn into borders.

Sowing new lawns or over-seeding dead patches can be carried out from mid-April to early May. If the soil is very wet or cold germination will be poor, so delay until the weather improves. Prepare the ground for sowing, by cultivating, levelling and lightly firming beforehand.

Do not walk over or mow newly sown grass until it has reached a height of 5-7.5cm (2-3in), and then only give it a light trim at the highest setting.

Apply a high nitrogen spring lawn fertiliser at the beginning of the month to encourage good, strong growth. If moss is a problem choose a combined fertiliser and mosskiller.

April is the best month to apply lawn weedkiller.

Lightly rake lawns with a spring-tine rake to remove old plant debris. This can also be done to rake out dead moss a couple of weeks after applying a chemical moss killer.

Repair bumps and hollows by peeling back the turf, removing or adding soil, and then replacing the turf.

Do not walk on newly laid turf, and leave it undisturbed for several weeks so that the new roots can establish.

Newly turfed areas can be mown with the blades set to the highest setting, as soon as the grass reaches 5cm (2in) in height.

Why not sow a wildflower meadow.

Contact: Scenic Blue Tel: 0116 250 5019 or www.scenicblue.co.uk

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