Gardening in April

If the weather is fair and grass is growing rapidly, give lawns their first cut of the season. Raise the height of your mower’s blades by a notch or two for the first cut, then gradually reduce the cutting height as the season progresses. Spot-treat large weeds such as dandelion and plantain with a selective lawn weedkiller.

To smarten up the lawn’s appearance, use a grass trimmer to trim grass along borders, then a half-moon edging iron to straighten up those edges. Tackle bare patches by loosening the soil, sowing grass seed and watering. On established lawns, applying a high-nitrogen weed and feed will green-up grass and kill unsightly moss, but check product instructions, because some can’t be applied for a brief period after a lawn has been cut.

Get more expert advice on lawn care here

In early spring, blossom, buds and new shoots on fruit trees can be harmed by frost, resulting in poor or damaged crops. If sub-zero temperatures are forecast, small fruit trees such as apples and pears, as well as soft fruit bushes, can be wrapped with horticultural fleece overnight. It pays to keep a close eye on weather forecasts at this time of year, and to have fleece to hand to keep fruit snug. Fruit grown in sunny, sheltered positions, and against south-facing walls, will be less vulnerable to damage.

Bedding plants fill hanging baskets, window boxes, containers and borders with colour all summer – and growing your own from seed is much cheaper than buying young plants at garden centres.

Many popular bedding plants such as busy Lizzies, French marigolds, petunias and geraniums can be sown now in heated greenhouses or on a window sill indoors. Fill pots and containers with a quality seed and cuttings compost, sow seed at the depth indicated on the packet, water lightly using tap water and place in a propagator. It won’t be long before signs of life emerge.

It’s one of the oldest clichés in gardening: the answer lies in the soil. And as all good gardeners know, it’s true! Improving soil now will pay dividends come summer, resulting in bigger crops and more flowers. Buy sacks of well-rotted manure and dig or fork it into border soil and vegetable patches (don’t let manure come into contact with stems of shrubs and plants). If you don’t have access to manure, the contents of your compost bin can work wonders. Open the access hatch at the bottom and if the material inside is brown and crumbly, it’s a nutrient-rich wonder that’s ready to be dug into soil.

Climbing plants head skywards as temperatures rise. Some, such as passion flowers, are masters of clinging on, using tendrils to firmly attach to supports. Others such as climbing roses and honeysuckle may need a little bit of help, especially if conditions are windy. Use garden twine or string to anchor new growth to supports. Installing trellis can help, too. Obelisks offer shelter and support for climbers while looking ornamental in borders.

If you have a greenhouse, sweet peppers are a must. They’re one of the easiest crops to grow and have a multitude of uses in the kitchen – adding flavour and crunch to stir fries, summer salads and fajitas. Red, green and yellow varieties are commonly available. Seeds should be sown as soon as possible this month, placing seed trays or pots in a propagator at around 20°C. Once the first pair of leaves have formed, seedlings should be pricked-out (transplanted) into pots. Sweet peppers thrive under glass, but can also be grown in containers outdoors after all danger of frost has passed.

Winter rain can wash nutrients from soil, so shrubs will thank you for an early season pick-me-up to replace goodness that has leached away. Forking a general-purpose balanced fertiliser such as Growmore into border soil will do the trick, encouraging flowers, foliage and root development. To stimulate roses into putting on healthy growth and plenty of blooms throughout summer, apply rose fertiliser to rose borders now.

Ponds are teeming with wildlife in spring, so it’s important to ensure that aquatic conditions are tip-top. Carefully remove twigs and debris from the water’s surface. Congested aquatic plants can be divided and re-potted into special plastic baskets filled with aquatic compost. If fish have little shelter from predators, install aquatic plants such as water lilies. Pond fish will become more active towards the end of the month as water temperatures rise, so start feeding.

April is a busy month for veg growers. There’s a host of edible plants to sow under cover now: cucumber, pumpkin, courgette, marrow and, if you didn’t get them started last month, tomatoes. For gardeners without a greenhouse, there are plenty of crops that can be direct-sown; early varieties of Brussels sprouts can be sown outdoors and protected with cloches, while other veg that can be direct sown includes carrots, leeks, parsnips, broad beans, peas and spring onions.

As light levels increase and temperatures rise, houseplants put on new growth. Increase watering and start liquid feeding – general purpose feeds such as Baby Bio cater for a broad spectrum of houseplants, while specific feeds are available for orchids and citrus. If a houseplant looks unhappy and has been in its pot for two or more years, it may need to be re-potted (roots bursting from drainage holes at the bottom of the pot are a tell-tale sign). Choose a slightly larger pot and fill with houseplant or loam-based compost. Never use houseplant compost for orchids though, which need an open, bark-based orchid compost that allows air to reach the roots.

If you’re keen to fill your garden with fabulous, showy flowers that bloom profusely all summer-long and carry on late into autumn, you can’t go wrong with dahlias. They come in all manner of shapes – cactus, pompon, decorative, ball, waterlily, single and many more – and are easy to grow, rewarding you with flowers that are worthy of the exhibition bench, even if you are new to gardening.

When is the best time to plant dahlias? Leaf through the pages of gardening books and they’ll advise you to plant dahlias in situ, when the risk of frost is over in late-May (or early June if you live in the colder north). But by starting these tender tubers off around Easter time, in pots indoors – or in a frost-free greenhouse or conservatory – you’ll be enjoying an abundance of booms earlier in summer.

To get dahlias underway, buy tubers as early as possible in April, while stocks are plentiful. You’ll be spoilt for choice, but Dahlia ‘Bishop of Llandaff’, with its vibrant red blooms and dark-bronze foliage, is an all-time favourite, while the pure-white flowers of ‘My Love’, a variety that flowers profusely, glow in borders at dusk on summer evenings, and ‘Pooh’ is a magnet for bees with its cheery red-and-yellow blooms.

To plant, choose generous pots with good drainage, and part fill with multi-purpose compost. Gently sit the tuber on the compost, at the depth stated on the packet, then top-up with compost and water lightly. Before planting out after the risk of frost, gradually acclimatise plants to conditions outdoors by placing outside by day and bringing undercover overnight, a process known as hardening off.

Choose a spot in full sun, planting into fertile, well-drained soil. Taller varieties will need staking as they grow, especially when in flower, as the weight of blooms can cause stems to buckle, especially in rainy or windy conditions. Feed once a month with a general liquid fertiliser (or a high-potassium feed such as tomato fertiliser) to keep flowers coming, and dead-head regularly to ensure that the show carries on into autumn.

Dahlias are relatively trouble-free, but slugs are partial to young shoots, so protect with organic slug pellets. Aphids can infest stems, so keep an eye out for trouble, and spray with a bug killer at the earliest opportunity. In mild regions, dahlias can be left in the ground over winter, protected by a generous application of mulch, but it’s not worth the gamble as severe cold or winter wet can sound the death knell. It’s better to lift dahlia tubers in late autumn. Carefully remove soil, and store in a frost-free place such as a garage.

Tomatoes are one of the nation’s favourite home-grown crops.  They are easy to start from scratch, and plants yield such heavy crops that a packet of seeds represents brilliant value for money. For unbeatable sweetness, try the cherry tomato ‘Sweet Aperitif’ – seed suppliers claim a single plant can produce up to 500 tomatoes! If blight is a problem in your area, the modern variety ‘Mountain Magic’ offers exceptional blight resistance, combined with a superior taste. If you only have room for a pot or hanging basket, grow tomato ‘Losetto’ F1, a superb cascading bush tomato that also has great resistance to blight.

Don’t be alarmed by tomato terminology: varieties described as ‘indeterminate’ mean that they are vine or cordon tomatoes, with one central stem that’s supported by a cane or string, and require sideshoots (that emerge from between leaves and the main stem) to be pinched out, to avoid unwanted foliage. Determinate varieties are bush tomatoes; compact varieties where sideshoots must not be pinched out or crops will be reduced.

To get tomatoes growing indoors or in a heated greenhouse during April:

1. Fill a seed tray or 9cm pot with seed compost and sow seeds on the surface, ensuring they’re evenly spaced apart. 
2. Cover with a light layer of compost and moisten with tap water using a mist sprayer. 
3. Place in a propagator at around 20°C until seedlings emerge, which usually takes a week. 
4. Once the first pair of true leaves have formed, ease the seedling and its root out of the compost using a pencil or dibber (always hold the seedling by its leaves, and never its stem). 
5. Then transplant individually into small pots of multi-purpose compost, growing on in a heated greenhouse or on a sunny windowsill.

After the danger of frost is over, tomatoes can be planted outdoors or in greenhouses. Under glass, plant into growing bags or fill large pots with multi-purpose or John Innes No 3 compost. Avoid letting compost dry out, as irregular watering can lead to fruit splitting, as well as a condition called blossom end rot. In greenhouses, liquid feed at least once a week using tomato fertiliser, once the first truss (stem with small green fruits) has set. Outdoors, begin to feed every seven to 14 days, once the second truss has formed.

If you’re looking for a tree that heralds the arrival of spring with a spectacular fanfare, then a flowering cherry fits the bill. Prunus ‘Tai Haku’ is one of the most magnificent, medium-sized tree that’s smothered in a profusion of large, single white flowers. Prunus ‘Kanzan’ is a sight to behold as winter’s icy grip gives way to spring. This classic, large, flowering cherry bears an abundance of vivid pink double flowers, creating a stand-out specimen tree that’ll be the talk of the neighbourhood every spring.