Strawberries

There are three kinds of strawberries:

• Alpine strawberries are usually grown in shade in ornamental gardens. They have small, sweetly-flavoured, aromatic fruits and tolerate cooler conditions than most other strawberries. They need no special care and can be left to fend for themselves after planting
• Large fruited ‘summer bearers’ flower in the short days of late spring for crops in summer, and to a much lesser extent in autumn
• Large fruited ‘perpetual’ strawberries form flower buds in summer to crop from late summer into autumn over a long period. Perpetuals bear fruit in regular flushes from July until the first autumn frosts. To ensure a good late summer crop, remove the first flowers of the season produced in May. Fruit size and yield reduces in the second year and they are best replanted annually

A bed of strawberries usually lasts up to four years if planted into well-drained, fertile soil free from troublesome weeds. To avoid disease build-up, choose a different plot and replant strawberries every three years. Strawberries will tolerate shade, but will thrive in sunshine, and they prefer a slightly acidic soil.

Before planting enrich the soil by digging in two bucketful's of well-rotted manure or garden compost per sq m (sq yd). Forking in a balanced fertiliser, such as Growmore, at 100g per sq m (3oz per sq yd.) will also help produce good yields.

Strawberries can also be grown in raised beds where drainage is poor.

Unless growing through polythene, protect the developing fruits from wet soil by tucking straw or special ‘strawberry mats’ under the fruit as they begin to swell. Some prefer to use barley straw as it is soft, but wheat straw is fine to use too.

If frost threatens, protect the early flowers overnight with horticultural fleece.

Planting

Strawberry plants are cheap and easy to plant:

• Plant in late summer or early autumn (no later than the second week of September in southern regions, or the first week of September in the north) or in mid-spring, into moist soil
• Remove flowers from spring-planted strawberries in the first season to encourage their roots to establish
• Crowns (the tops of individual dormant plants) should be at soil level, 40cm (16in) apart in the row with 1m (3ft) between the rows
• Many gardeners grow strawberries through polythene, ideally white, with black on the underside, but any plastic mulching film will do. This suppresses weeds, conserves water and stops soil splashing on the fruit
• An irrigation system, such as a leaky pipe, installed under the sheeting also helps maintain moisture

Sowing alpine strawberries from seed

• Sow either in autumn or spring using seed pots containing John Innes No 1 or a multi-purpose compost. Ensure the compost is fine and firmed prior to sowing
• Sow seed on the surface and lightly cover with sharp sand
• Cover with glass to maintain humidity and shade until germination; autumn-sown seeds should be overwintered in a cold frame
• Germination requires temperatures between 18-21°C (65-70°F), and can be slow and erratic
• As soon as the seedlings have two true leaves and are big enough to handle, prick them out 2.5cm (1in) apart
• Plant out in May, into an open or lightly shaded spot.

After harvest

• After the final harvest of the summer, tuck spare runners (young plants that develop as offshoots from the parent) into the row to fill in gaps or replace old plants. Remove any unwanted runners
• Some gardeners prefer a continuous row in the second and third year rather than spaced plants; the total yield may be higher, although the quality of the fruits is not so good. Whatever method used, try to keep the gap between the rows clear to get at the plants for weeding and harvest
• Cut off the old foliage of summer bearers after cropping has finished, cutting to about 10cm (4in) above the crown to allow the new leaves to come through
• Reduce pests and diseases by clearing away the cut foliage and any straw or other debris from around the plants
• Nets will be needed to prevent birds stripping the fruit, but remove nets after harvest to allow birds to feed on remaining pests. Use 2cm (¾in) or 2.5cm (1in) plastic or other synthetic netting, and support the nets by a system of posts and wire or polypropylene string, making the cage 1.2m (4ft) high to allow access for picking
• Don't cut back perpetual-fruiting cultivars; just remove the old leaves in autumn
• Little feeding is required, but you can apply sulphate of potash by the end of January at 15g per sq m (approx 0.5oz per sq yd) in order to raise potassium levels. Where plants seem to be growing poorly add a general-purpose fertiliser such as Growmore at 35g per m² (1oz per sq yd) after harvest, taking particular care to avoid the crown, as fertilisers can scorch

Strawberries are easy to grow in containers. Peat-free multipurpose compost is a good choice. Suitable containers include grow bags, hanging baskets, troughs and tubs. Healthy productive plants are sadly difficult to achieve in the traditional strawberry pot.

Container cultivation avoids the build-up of soil problems, but vine weevil control is often essential. See the problems section below for further detail.

Greenhouse cultivation

Strawberries grown in a heated greenhouse can produce fruit as early as mid-March, although for high quality and well-coloured fruit it is better to aim for harvest about a month later.

Suitable cultivars for forcing under glass include ‘Cambridge Favourite' AGM, ‘Honeoye' AGM, ‘Rosie’, ‘Royal Sovereign' and ‘Tamella'.

For March harvesting, bring container plants into the greenhouse in mid-December, but give no heat or water until the first new leaves appear, except for spraying or syringing on sunny days. During early growth, keep the atmosphere moist and restrict ventilation to sunny days when it is necessary to avoid overheating. Increase watering as the foliage develops.

At the end of December, start to give gentle heat and keep the night temperature at about 7-10°C (45-50°F). Too much heat will result in excessive foliage at the expense of flowers.

In February when the flowers open, increase the temperature to 15°C (60°F) and give ventilation during the day, although generally maintaining a moist atmosphere except at pollination time. Hand pollinate daily with a soft paintbrush to ensure good setting and fruit shape.

When the fruit has set, increase the temperature to 18°C (65°F). For the highest quality fruit, thin the flowers by removing the smallest ones immediately after the petals have fallen, leaving 8-10 fruits to mature.

Reduce ventilation and keep the atmosphere thoroughly moist at all times until ripening begins. Water copiously and syringe frequently in sunny weather to promote large fruits and discourage mildew. As the fruit colours increase ventilation, reduce watering and stop syringing altogether to reduce the risk of fruit rot.

Apply a half-strength liquid feed every 10-14 days until the fruit begins to colour. Too much feeding will result in soft, tasteless fruit and increase the risk of rotting. The fruit should be ready to pick after mid-March.

April harvesting:

• Bring containers into the greenhouse in early January
• Start gentle heat about three weeks later, maintaining a night temperature of 4-8°C (40-45°F) until flower trusses begin to appear in February, then raise it to 10°C (50°F)
• Hand pollinate as described above and follow the same watering and feeding regimes
• After petal fall, increase the temperature to 13°C (55°F). Once ripening begins a lower temperature will improve colour and flavour but slow down the ripening process
• Fruit should be ready for picking from mid April

For late April to early May harvesting, bring plants into an unheated greenhouse in February, and follow the steps for April harvesting.

Strawberries can be propagated in late summer, but no later than early autumn:

• Sink 9cm (3.5in) pots, filled with multi-purpose potting compost, into the beds and insert individual runners into them
• Peg down with U-shaped pieces of thin wire, about 15cm (6in) in length
• Keep well-watered to promote root growth
• Sever the new young plants from the parent plant when rooted

Perpetual strawberries produce few runners and new plants are best bought in annually.

Seed-raised cultivars are available but are not recommended, except for alpine strawberries.

‘Honeoye’ AGM: This is a moderately heavy-cropping cultivar that fruits very early, producing good-sized, good quality fruit. Suitable for cloches and tunnels.
‘Rosie’: This is a very early summer bearer with good flavour.
‘Tamella’: This heavy cropper produces very large, firm fruits with a good flavour.
‘Royal Sovereign’: This is a moderate cropper with a very good flavour. It is, however, susceptible to mildew, botrytis and virus infection.
‘Cambridge Favourite’ AGM: This is a widely grown, reliable plant which crops well, producing medium to large fruits. Mid-season.
‘Pegasus’ AGM: A mid-season, reliable cropper, producing lots of medium-sized fruits.
‘Hapil’: Crops well on light soils and under dry conditions, producing large, attractive fruits with good flavour.
‘Elsanta’: Heavy crops of large, firm berries of good flavour. Susceptible to mildew and verticillum wilt; spray against mildew and plant under warm soil conditions to avoid wilt.
‘Cambridge Late Pine’: Moderate cropper, produces medium-sized fruits with an excellent flavour.  Susceptible to mildew and virus infection.
‘Eros’: A mid-season heavy-cropper, producing fruits with good flavour.
‘Rhapsody’ AGM: A late-fruiting variety producing good crops of medium-to-large fruits. Resistant to red core. Does well in the north and in Scotland.
‘Symphony’ AGM: This is a reliable and heavy cropping summer bearer, cropping in late summer with good flavour.
‘Florence’:  A late-summer strawberry with good disease resistance. The large, bright, glossy fruits have good flavour.

Perpetual strawberry cultivars

‘Aromel’ AGM: This is a moderately heavy cropping perpetual strawberry with very good flavour.
‘Calypso’: Medium to large fruits with moderate flavour.
‘Mara des Bois’: Well-liked for its crop of intensely flavoured fruit that is said to be reminiscent of wild strawberries.
‘Bolero’: A good cropper, with some resistance to mildew and wilt.

Alpine strawberry cultivars

‘Alexandra’: Fruits long and large for an alpine strawberry.
‘Baron Solemacher’:  Heavy cropper, good flavour.
‘Fraise des Boise’: Prolific, continuous cropper. Fruits very small; good flavour.
‘Golden Alexander’: Small, rich flavour.
‘Mignonette’: Heavy yields; exceptionally sweet and aromatic.
‘Rügen’: Productive, large-fruited aromatic variety.
‘Yellow Fruited’: Golden yellow, strongly flavoured. Moderate cropper.

Links

RHS Find a Plant
RHS Fruit AGM list

Strawberries can suffer from a range of problems, from bird and slug damage to specific problems such as strawberry virus and strawberry black eye. Fruits may occasionally be affected by phyllody. The fruit fly - spotted wing drosophila (SWD) - is likely to become an increasing problem.

They may also suffer cold damage.

Container grown strawberries can be troubled by vine weevil.

For strawberries grown under glass, aphids and red spider mite are the most troublesome pests, while mildew and grey mould might also be a problem.

Blueberries
Fruit in containers
Goji berries
Gooseberries, red and white currants
Grow your own: Strawberries
Hedgerow fruit
Raised beds
Raspberry
RHS video: Growing strawberries