April makes its own rules and can dictate play for the rest of the year. Alys Fowler lists some of the essential tasks to do in the garden this month to ensure that you are prepared as possible.
April makes its own rules and can dictate play for the rest of the year. Some years it can be so warm you can put your shorts on and plant out tomatoes before the month is out. Other years it's mainly wet and grey. Whatever the state of play there is plenty to be pricked out, potted up and moved around.
• If the weather is kind, April is the month of lovely flowering trees and shrubs such as Magnolia stellata, M. x soulangeana, M. Pieris, Malus, Prunus, Spiraea, Ribes and Amelanchier.
• The old adage ‘April showers brings May flowers’ stands because this is a month in which water matters a great deal. Warmer weather means a greater rate of transpiration – don’t let young or new plants wilt as this has a knock-on effect in later months.
• At the end of the month start to stake and tie-in delphiniums. You can thin crowded clumps down to four to six good-sized shoots. The thinnings, if not too hollow, make good cuttings. Place cuttings around the edge of a pot with free-draining compost. Keep the cuttings in a greenhouse or cold frame.
• This is a good time to divide late-flowering perennials such as Aster, Rudbeckia, Vernonia and Eupatorium. Lift and separate into good-sized pieces, discarding any congested, woody centres. Replant in good soil with well-rotted compost.
• Towards the end of the month plant out firm, healthy dahlias. You’ll have to protect the new shoots from any errant late frosts and put down slug traps as tender shoots are too tempting.
• Early flowering bearded irises look stunning in a vase. Pick the bloom early in the morning and stand in hot water to seal the ends before transferring to cold water.
• Be vigilant against slugs, as they can make light work of iris flowers at this time of year.
• Plant out autumn-sown sweet peas if you’re further north and spring-sown seedlings in the south. If growing as cordons, start restricting growth by removing tendrils and side shoots to encourage more flowers.
• Continue to sow hardy annuals outdoors. Nasturtiums are particularly useful for bare patches in herbaceous borders or under trees as they provide rapid ground cover. Use them as a cover-crop in the vegetable garden to lure hungry caterpillars from your cabbages.
• Remove spent flower heads of daffodils and tulips, but keep seedpods intact on Muscari, Scilla and other small bulbs so that they can naturalise. Plant out any young arum lilies in mild areas.
• Newly established trees will need to be watered in dry months. Mulch with lawn clippings or bark mulch to suppress weeds and keep water in.
• You can lightly prune spring-flowering shrubs and trees that have finished blooming.
• This is the last chance to cut back hard those shrubs that flowers on this year’s growth, such as buddlejas and hydrangeas. You can remove weak growth of Magnolia grandiflora, Euonymus, Viburnum and evergreen Olearia now. Also give straggly lavenders a quick haircut.
• Cut back heathers that have finished flowering, otherwise they start to look leggy. Propagate now through heel cuttings or layering.
• Complete sowings of home-saved half-hardy annuals.
• Remember to keep coldframes covered overnight as there can still be harsh frosts. If the frost has got in, spray with cold water and cover the frame with a blanket. By lunchtime, plants should have defrosted intact.
• For every cold night there will be a bright day, so shade young seedlings and newly potted plants.
• Keep your greenhouse well ventilated and start monitoring for aphids, thrips and mealy bugs.
• From the middle of the month, plant out indoor tomatoes, peppers and aubergines into greenhouse beds and grow-bags.
• Make further sowings of basil and tagetes to plant with tomatoes.
• You should be enjoying the first cuts of asparagus and broccoli now. Carry on picking broad beans, and start to harvest cloche-sown lettuce and radish.
• Under heat, continue to sow aubergines, peppers, cucumbers, pumpkins, winter squash and tomatoes.
• Under cover, sow dwarf beans, celery, celeriac, summer and autumn cauliflowers and hybrid broccolis.
• In warm areas, later in the month, sow courgettes, kales, sweet corn and tomatoes. Start to make succession sowings (every two weeks) of fast-maturing crops of beetroots, radish, lettuce, spring onions, salad rocket.
• In the open, sow broad beans, globe artichoke, sprouting broccoli, kales, land cress, leeks, orache, parsnip, peas, salsify, swedes, spinach beet, turnips, carrots and calabrese. If you are limited for space, module-sow outside (you don’t need a coldframe, just something to keep slugs at bay) and plant out as space becomes available.
• Mix different cultivars of radish such as ‘French Breakfast’ and ‘Cherry Belle’ so that you get a variety of styles at any one picking. If you’ve got limited space, this makes for a more interesting salad.
• Likewise pak choi and carrots make a good space-saving mix. Use a roughly 50:50 mix and thin as necessary.
• In frost-prone areas you can now plant out late-flowering strawberries.
• Mulch and water any newly planted fruit.
• Keep nectarines and peaches covered against leaf curl. If pollinating insects can’t reach flowers then hand-pollinate (a bit of rabbit fur or a paint brush works best). The pollen is ripest at midday. Spray with a fine mist of water to ensure setting.
Continue to sow small amounts of dill, fennel, oregano, thyme and parsley. Thin March sowings.
• Unfortunately regular mowing is now necessary. Start to lower the blades at each successive cut. Don’t go too low, though, as this will just mean more cutting. If your lawn gets heavy traffic it’s a good idea to aerate, scarify and apply an organic spring fertiliser so that it goes into summer in top shape.
• Now is a good time to level any lumps and humps in a lawn. To raise a dip take a fork and sink it into the lump at a roughly 45˚ angle and heave the turf up. Brush a sand-and-loam mixture into the holes. Continue to do this until the dip is level. To level a hump, cut an H shape in the turf and roll back the sides to expose the soil. Remove the excess soil, then replace the turf and firm it back. You can sift a little soil and grass seed into the cracks.
This article, written by Alys Fowler was originally published in April 2010. Alys Fowler studied horticulture at Wisley and is now a regular columnist for the Guardian Weekend. Alys won The Dr David Hessayon Garden Columnist of the Year Award at the Garden Media Guild 2015 for her Guardian Weekend column.