Expert Gardening Tips For April 2019
15% DISCOUNT ON OUR GROW YOUR OWN COLLECTION FOR APRIL.
ENTER CODE GYO15 AT THE CHECKOUT. FREE UK DELIVERY. VALID UNTIL 30 APRIL 2019. CANNOT BE USED WITH ANY OTHER DISCOUNTS OR VOUCHERS.
March this year has turned out to be hugely different weather wise than March 2018 when we had weeks of cold weather & snow disruption. The past couple of weeks have seen some glorious sunny weather much needed as an antidote to the depressing political stalemate that the UK has found itself in. Most of the Spring flowering trees & shrubs such as Camelias & Magnolias are either over or in full flower considerably earlier than usual. With a late Easter we will be lucky to still see a few Daffodils about.
Below are our suggestions for getting the most out of your garden in April prepared exclusively for us by a leading horticultural expert.
All container-grown trees, shrubs, climbers, fruit and roses can be planted this month.
Make sure the soil is well prepared before planting. Dig in plenty of organic matter, such as well-rotted manure, compost, composted bark or tree planting compost. Mix in more organic matter with the soil dug out from the planting hole.
Always plant at the same depth that the plant was originally growing and firm the soil around the roots.
Trees will need to be staked with a good tree stake and secured with two tree ties.
Water in well and water in dry weather, as the plants won’t have much time to establish before the summer.
After planting, mulch the soil around fruit trees and bushes with a 5-7.5cm (2-3in) thick layer of organic matter to help keep weeds down and maintain soil moisture levels in summer.
Don’t rush to replace or prune plants damaged by frost or snow in winter. Leave them alone until you see fresh new growth appearing. Then cut off any dead growth from shrubs, cutting back to a healthy new shoot or growing point, and tidy up the leaves of perennials. Give a liquid feed to help them recover.
Give all plants the best start to the year by feeding them now.
Sprinkle the fertiliser evenly around the root area (not at the base of the main stem) and work it into the topsoil. If the soil is dry, water in the feed to prevent it burning the roots.
Controlled-release fertilisers are the easy way to feed and forget as they release their nutrients whenever the soil is warm and moist enough for plant growth, and will feed the plants for several months from one application.
Mulch the soil around plants with a thick layer of organic material – such as composted bark, compost or bark chippings. This will help keep weeds down, as well as helping to keep the soil moist in summer and insulate roots from temperature extremes. For best results the mulch needs to be 5-7.5cm (2-3in) thick.
When planting up containers add a controlled-release fertiliser and water-retaining gel to the compost for simple feeding and watering.
You could even put up a micro-drip watering system for even better results – and enjoy an easier life.
Check containers regularly to see whether they need watering. Even at this time of year, they can dry out quite quickly.
Before spring gets into full swing make sure you’ve carried out any cleaning and repair jobs. This includes cleaning the patio and growing frames, preserving and staining wooden features and cleaning out water butts and other watering equipment.
Keep an eye out for weeds and deal with them quickly before they get out of control.
Annuals and small weeds can be hoed on a dry or windy day. Make sure the blade of the hoe is sharp as the aim is to cut through the weeds’ stems.
Larger infestations and all perennial weeds, especially those with creeping roots, are best treated with a weedkiller based on glyphosate, which will kill the roots as well as the top growth. You’ll get better results if you spray in the evening.
Use all your weeds, lawn clippings and other garden debris to make garden compost. Mix grass clippings with coarser material to ensure your heap doesn’t turn into a sticky mess.
As the weather warms up, pests and diseases will be stirring in the garden. Keep on top of any problems that do occur to ensure they don’t get out of control – early eradication is the key to success.
Ready-to-use sprays do away with fiddly mixing and ensure you have something ready to deal with the problems as soon as they are seen.
Slugs and snails are a major problem at this time of the year. Make sure you protect susceptible plants. – especially hostas, delphiniums and vegetables.
Sprinkle slug pellets, place barriers or water on a liquid slug killer.
Frosts are possible this month, so make sure tender plants like young bedding plants and tomatoes are protected from the cold. Always have horticultural fleece on hand that can be thrown over the plants at night when frost is forecast. Fleece can even be used to give cold protection for plants in greenhouses, frames and cloches.
Grow Your Own - Fruit
Plant outdoor grape vines, once all risk of frost has passed. Grapes need a deep, well-drained soil.
Sow melon seeds in small pots of compost, one or two seeds per pot; if two seeds germinate carefully remove the smaller of the two. You will need a heated propagator or a warm place for good germination.
Give fruit growing in pots a liquid feed using a balanced fertiliser or treat them to a once-a-year feed with a controlled-release fertiliser.
Begin feeding citrus plants with a spring/summer citrus feed, or using a high-nitrogen feed with added trace elements.
Feed blackcurrants, blackberries and hybrid berries with a high nitrogen fertiliser.
Grape vines on sandy, nutrient-poor soils, may benefit from feeding with magnesium sulphate (60g per sq m) or a foliar feed of Epsom salts, to prevent magnesium deficiency.
If possible, protect plum and pear flowers from late frosts, but allow insects access for pollination.
Place cloches or fleece over outdoor strawberry plants to force an earlier crop. During the warmest part of the day, make sure insects can get at the flowers to pollinate them. High potassium feeds will help encourage flowers and fruit.
Pinch out lateral shoots on grape vines to leave one lateral per 30cm (1ft) of stem. Tie in shoots to the supports.
Before the buds break, remove stems of wall-trained figs that are growing into or away from the support. Tie in the remaining shoots to the supports.
Towards the end of the month it’s safe to prune plum and cherry trees, if necessary – but only prune if it’s really necessary. These fruit are vulnerable to silver leaf and bacterial canker diseases if pruned too early in spring. Always cut back to a strong, healthy shoot or growing point.
If you have been forcing rhubarb plants, take the last crop of stems, feed with a general fertiliser, and leave them uncovered to grow without cropping for the rest of the year.
Keep temporary shelters in place over peach and nectarine trees, to protect against peach leaf curl.
Net fruit crops to reduce pigeon damage, and to keep bullfinches off fruit buds.
Several fruit pests and diseases may start attacking this month, so check plants regularly and deal with any pests accordingly. Ones to be wary of include:
Pests: aphids, especially plum leaf-curling aphids and currant blister aphids, pear midge, red spider mite on fruit growing under glass.
Diseases: American gooseberry mildew, apple and pear scab.
Blackcurrants are vulnerable to big bud mite, which can spread blackcurrant reversion virus. Affected plants must be dug up and disposed of. Try growing resistant varieties, such as ‘Farleigh’, or ‘Ben Hope’.
If you are going to spray against pests or diseases, spray late in the evening when few pollinating insects are about.
Grow Your Own - Veg
Nearly all outdoor vegetables can be sown this month. Sow salad and quick maturing crops little and often for a continuous supply. Sow thinly within the row to reduce the need for thinning out once the seedlings are growing well.
Fleece and polythene covers or cloches can be used to protect early outdoor sowings if the weather is cold. Some vegetables (such as beetroot) can bolt (go to seed) if sown outside too early in the cold without protection.
Sow brassicas in a separate seedbed to produce young plants for planting out to their cropping position in May/June. This includes broccoli, cauliflowers and cabbages.
Peppers, tomatoes, cucumbers, aubergines, celery, courgettes, pumpkins and squashes, French and runner beans and sweetcorn can all be sown indoors with gentle heat, preferably in a propagator.
In mild areas you may be able to sow dwarf French beans and sweetcorn directly outside under cloches or fleece; in colder areas wait until May.
Pot up tomato and other seedlings into small pots when they develop true leaves above the more rounded seed leaves. Carefully lift them from the compost with a dibber or similar, holding the plants by the leaves rather than the stem as this can be easily damaged. After transplanting, water in well and grow on at a minimum temperature of 10-15C (50-60F).
Tomatoes can be planted into their final cropping pots or growing-bags once the first truss of flowers has set.
Plant out early potatoes in the first half of the month and maincrop potatoes in the second half. Potatoes can be planted in trenches or in individual planting holes, with 5-7.5cm (2-3in) of soil on top. Or, plant them through slits in black polythene sheeting. They can also be planted in containers or potato bags.
If you planted out seed potatoes last month, they may be ready for earthing up to protect the young shoots from cold and frosts. 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 light. If frost threatens, cover the shoots with horticultural fleece for further protection.
Plant asparagus crowns. A good, deep, well-drained soil with plenty of organic matter is best for this long-term crop. Plant on a mound of soil and spread out the roots evenly.
Plant shallots, garlic and onion sets plus Jerusalem artichoke tubers.
Broad beans grown in pots under cover earlier in the year can be planted into their cropping position in the garden. Tall varieties will need some form of support; place bamboo canes at the ends of the rows and weave string in between the plants and tie off each end to the canes.
Prepare a runner bean trench ready for sowing (in May) or planting out (in June). Dig the trench about 15cm (6in) deep and start filling with garden and kitchen waste, crumbled up newspaper and even torn up cardboard. The trench can be covered over with soil just before you’re ready to sow or plant. The material in the trench will hold on to water and ensure a bumper crop.
Keep a close eye on plants, especially, young plants, for problems with developing pest problems. Aphids can soon get out of hand and flea beetles will attack a wide range of seedlings, especially brassicas.
Slugs can be a problem at any time, so ensure slug controls are in place.
Pick yellowing leaves off brassicas to prevent spread of grey mould and brassica downy mildew.
Damping off of seedlings can be a problem with sowings in containers. Clean equipment and, where necessary, use of a copper-based fungicides can help to control this problem.
Herbs are not only good to grow for the kitchen – many also have colourful flowers and foliage, so plant some now. Sow basil, parsley, chives, coriander and dill seeds in the greenhouse or on the windowsill.
Seed of hardy annuals can be sown outdoors now where you want them to flower or, better still especially in cold areas, in pots or cell trays indoors.
There are lots to choose from including Calendula (pot marigolds), Eschscholzia (Californian poppies), Limnanthes, Lobularia and Nemophila. You can even try annual grasses, such as Briza maxima, Lagurus ovatus and Hordeum jubatum.
In mild areas, sow directly outside. Marking out irregularly shaped seedbeds and broadcasting drifts of different seed gives a more natural look. However, you may find it easier to sow in rows in these shaped areas; this makes it easier to distinguish between flower and weed seedlings as you know where the flowers have been sown.
If you started sowing hardy annuals early indoors, you may have modules of young hardy annuals now ready for planting out.
Sweet peas can still be sown outside this month and you can plant out autumn-sown sweet peas.
Half-hardy annuals can be sown indoors with gentle heat this month, ready for planting out at the end of May/early June. There are dozens of different types to grow. Sow in seed trays and then carefully transplant the young seedlings, holding them by the leaves not the stem, individually into small pots or regularly spaced out in seed trays, when they’re large enough to handle. Grow them on at a temperature of 10-15C (50-60F) keeping the compost moist, ready for planting out at the end of May or early June, after the fear of frosts.
You could even try sowing annual climbers, which make colourful colour screens and are useful for hiding unsightly garden eyesores. Good choices include asarina, eccremocarpus, cobaea, ipomoea, tropaeolum and rhodochiton.
Prick out seedlings of tender bedding plants and pot up young plug plants and cuttings so that they can grow into sturdy plants ready for planting out towards the end of May.
Always use fresh potting compost and make sure that seed trays, pots and cell trays are either thoroughly cleaned – or buy some new ones.
Plants will need hardening off – acclimatising to the outdoor conditions – for around seven to 10 days before planting out, and they can be protected from cold, wind and light frosts with horticultural fleece.
Check that seedlings or young plants in pots on windowsills do not become leggy or lopsided by turning the pots through 45 degrees every day to make sure that they receive an even ration of light on all sides.
Although it’s too early to put summer hanging baskets and containers outside, you can plant them up now. Doing this now means the plants will be a good size, the container will be covered and the plants will already be in flower or close to flowering when you put them outside. You’ll need to keep them inside where they’ll get good light and protection from frost.
Deadhead daffodils and other spring-flowering bulbs as the flowers fade. Just pull off the heads, leaving the stems and leaves; never tie the leaves in knots – allow the foliage to die down naturally. Give them a liquid feed every two or three weeks to help build up their strength for next year. By looking after the plants in this way you can ensure a quality display next year.
Bulbs that didn’t perform well this year may need to be lifted, the clumps of bulbs split up and the bulbs replanted in well-prepared soil that has had plenty of organic matter added to it.
Plant out forced daffodils, crocus and hyacinths that you’ve had in pots in the house. Plant firmly and water them in with a liquid feed. Allow the foliage to die down naturally.
Feed polyanthus, pansies, double daisies and other spring flowers to keep them flowering well.
Lift and divide your best primroses and polyanthus once they’ve finished flowering, checking carefully for any vine weevil grubs among the roots. Replant in well-drained, humus-rich soil and water well; keep well watered until they’re established.
April is a good month to plant herbaceous perennials – there are so many to choose from and they’ll provide flowers and colour for months on end.
To get the best out of them, make sure you dig over the soil, remove any perennial weeds and then dig in plenty of organic matter, such as planting compost. Plant firmly and water in well afterwards.
A 5-7.5cm (2-3in) thick mulch of planting compost placed around the plants afterwards will ensure they get off to the best possible start and will help keep weeds down.
Tall and floppy herbaceous plants – especially those in windy and exposed gardens – will need some form of support –such as twiggy shoots or metal supports. Putting plant supports in place now will help prevent problems later on when it’s difficult or impossible to do anything about it and the plants will grow up through them, covering them discreetly.
Then carefully tie in the stems as they develop with soft string or similar, criss-crossing the strings between the supports.
For a riot of colour you can’t beat summer-flowering bulbs. Lilies especially are perfect for bringing colour, and scent, to the garden – but there are lots of other types to choose from.
Prepare the soil first and, in poorly drained soils, place a 2.5cm (1in) thick layer of grit or gravel in the bottom of the hole to improve drainage and prevent the bulbs rotting.
Plant dahlia and canna tubers in 12.5cm (5in) pots to give them a flying start, but keep them frost free. In warm regions or towards the end of the month they can be planted outside.
Plant gladioli corms over several weeks for a succession of flowers.
Take cuttings from fuchsias, pelargoniums and other half-hardy perennial bedding and patio plants. You can either use newly bought plants or those kept over the winter. Cuttings should have two pairs of mature leaves and be inserted in fresh, gritty compost then watered and covered with a polythene bag to keep the humidity high. Put them on a windowsill that does not get any direct sunlight or in a heated propagator until they root.
Trees, Shrubs, Roses & Climbers
April is a good time to move evergreen shrubs that have grown too tall or are growing in the wrong place.
Prepare their new site well beforehand, water the plant thoroughly the day before, dig up as big a rootball as possible and transfer to its new home, planting at the same depth it was originally growing and firm the soil around the rootball. Water in well and keep well watered during dry periods for the first year.
Tall plants may need to be staked to keep the roots firm while they’re establishing. In windy sites it pays to protect the foliage by erecting a windbreak around the plant.
Prune spring-flowering shrubs, like forsythia and flowering currant, after they’ve finished flowering. Aim to completely remove one in three of the oldest flowering shoots and cut back some of the remaining shoots too.
Shrubs that are stooled (cut back hard) to keep their larger or more colourful foliage (such as Cotinus, Eucalyptus and Sambucus) are cut back this month. Eucalyptus can be cut back to strong growth just a few inches above ground level if necessary. Cotinus and Sambucus should have the stems produced last year cut back by around half.
Lightly cut back or trim over lavender, Helichrysum (curry plant), Santolina (cotton lavender) and thyme. This will keep them bushy and flowering well. Never cut back into old, woody growth as these plants rarely re-shoot from old wood.
Cut back penstemons and other slightly tender plants such as Artemisia, Phygelius and Teucrium. They can either be cut back hard, to just above new growth appearing at or just above ground level, or reduced in size by about half.
Clip over winter-flowering heathers as the flowers fade to prevent the plants getting straggly. Remove the faded flowers plus about an inch of leafy growth.
Feed all shrubs after pruning to encourage strong regrowth that will flower later. A granular fertiliser is best.
Remove reverted green shoots from variegated evergreens. These shoots, being stronger than the variegated ones, can soon take over and spoil the overall appearance of the plant. Cut them back to where variegated foliage starts or remove them completely.
Prune small-flowered spring-flowering clematis, such as C. montana, C. alpina and C. macropetala, immediately after flowering. This will help keep them tidy and prevent ‘bird’s nests’ of tangled growth later in the year.
Guide the new shoots of clematis and other climbers in the direction you need them to grow. Make sure the shoots provide a good, even coverage of their support. Then carefully tie them in with string or similar material.
Try to tie in climbing and rambling roses, as well as shoots of other climbers, as near to horizontal as possible. Or, if more suitable, into a fan shape. This reduces the growth of the shoot and, as a result, encourages more flowers.
Give conifer hedges their first cut now before they start to get out of hand.
Spray roses regularly with a suitable fungicide to prevent black spot, rust and mildew diseases.
Make new lawns from turf or seed. Once the site is forked over and lightly fed, the most crucial point is to get it level. It's too late once the grass is down. A combination of treading and raking should do the trick.
April is one of the best months to start a new lawn from scratch – the soil is warming up and is nicely moist. Improve the soil first with composted bark or similar, remove large stones and other debris, lightly consolidate it by walking over the area with your weight on your heels, rake it level, add some general fertiliser, rake it again and you’re ready to start sowing. We stock a number of different seed mixtures for a range of different lawn types.
Grass should be growing strongly now so make sure you mow regularly – probably weekly aiming to keep the grass around 2.5-4cm (1-1.5in) high. Adjust the cutting height of your mower so that it takes off no more than half the length of the blades of grass at a time.
While you’re mowing, take note of bare patches, moss invasion and weeds and deal with any problems you see.
Cut lawn edges with a half-moon edging iron to ensure they look neat and well shaped.
Feed lawns with a granular lawn fertiliser or use weed and feed or weed, feed and mosskiller where these are a problem.
If weeds are a real problem it would pay to treat them with a liquid lawn weedkiller.
Increase the watering of indoor plants as the days get longer and warmer. Check plants every few days.
Feed houseplants every seven to 10 days with a liquid houseplant fertiliser.
If roots are peeping through the holes in the base of the pots repot into a larger size. Flowering houseplants usually perform better if they are kept slightly potbound.
Make more African violets by carefully pulling off individual leaves with most of the stem and pushing them into small pots of fresh compost.
Cut the babies off spider plants and put them into individual pots to make new plants.
Content Copyright Heritage Gardens 2019.