Soil and Situation. Strawberries succeed best in rich soils. They will grow well in heavy loam if good winter drainage can be assured. Phosphates have a marked effect on growth. Soil should be deeply dug, enriched with manure or compost at 1 cwt. to 12-15 sq. yd., and dusted with basic slag at 6 oz. per square yard and sulphate of potash at l oz. per square yard. Lime is not essential.
ALPINE STRAWBERRIES do not as a rule make runners and are increased by seed. These are sown in March in a cool greenhouse (average temperature 55°) in ordinary seed compost. The seedlings are pricked off into boxes as soon as they can be handled conveniently and then transferred to a frame and gradually hardened off for planting outdoors in early summer.
Planting. The best season is August and early September. Failing this, pottgrown runners can be planted in March. These should not be allowed to fruit the first season. Space plants 11 ft. apart in rows 21-3 ft. apart. On heavy land, draw the soil into low ridges 2 ft. apart and plant along the summits of these. Be careful not to bury the crowns below the surface. Roots should be just covered and crowns on the surface.
Pollination. A few varieties produce no pollen and consequently no fruits unless other pollen-bearing varieties are planted with them. Others are self-sterile, i.e. they produce pollen, but this is not effective for their own pollination. All these must be interplanted with other varieties. Few such varieties are cultivated in gardens nowadays, having been discarded in favour of self-fertile varieties, but Huxley Giant is grown commercially.
Routine Cultivation. All runners must be cut off during the summer months unless required for propagation. Soil should be kept clean by frequent hoeing, but digging or forking must not be attempted, because many roots are produced near the surface. Clean straw must be spread between plants in May to conserve moisture and preserve fruits from mud splashes, or strawberry mats may be used.
Each March top dress with a mixture of six parts by weight of superphosphate of lime, three parts of sulphate of potash, and two parts of sulphate of ammonia, at 3 oz. per sq. yd.
Routine Pest Control. Usually unnecessary, as foes are dealt with as noted. Dust with flowers of sulphur if mildew appears; burn off straw on the beds when the crop has been gathered to destroy old foliage together with possible pests and fungi. This should be done on a dry, breezy day, so that the straw burns quickly. If red spider or tarsonemid mite is troublesome, spray with lime sulphur at summer strength, about the third week in March. Use captan or thiram to control grey mould, but not if fruit is to be preserved in any way.
Propagation. Strawberries soon deteriorate, and beds are rarely worth keeping after their third year. Usual practice is to remake one-third of the bed each year, so that the whole plantation is renewed every three years. Propagation is effected by runners produced throughout the summer. These should be selected from the best plants only, chosen for health and good cropping. Retain five or six runners per plant. Pinch the tip out of each just beyond the first plantlet formed on it. Peg this plantlet firmly to the soil or fill a small flower pot with loamy soil, plunge to its rim near the parent plant and peg the runner into this. Propagation should be done in June or July. If kept moist, each plantlet will produce roots by the middle of August, when the runner joining it to the parent plant may be severed. A week or so later lift and replant in fruiting quarters, or, alternatively, pot and winter in a frame for spring planting.
The Alpine varieties of strawberry, which produce small fruits during most of the summer and early autumn, do not make runners and are usually raised from seed. The largetfruited perpetual strawberries produced by crossing Alpine varieties with normal large-fruited strawberries do make runners but not always very freely.
Forcing. Strawberries can be gently forced to fruit a month or more ahead of normal time. Strong runners should be rooted in June and potted singly in 4 or 5-in. pots in August. Use an ordinary potting compost, place pots on ash base in a frame, shade for a week, but give no further protection till October. Then use lights to ward off extreme wet and snow, but ventilate freely whenever possible. Remove pots to a cool greenhouse (temp. 40 degrees-) from January to March according to the time at which fruit is required. Water with increasing freedom as growth proceeds. Hand fertilize flowers with camel-hair brush. From the time plants come into flower, temperature may be increased gradually to a maximum of 70 degrees to be reached as the fruit swells. Drop to 60-65 degrees for the last few days. Cooler conditions may be maintained throughout if it is not desired to hurry ripening unduly.
Cloches of the continuous barn type may also be used to cover strawberry plants growing in the open. They should be placed in position about mid-February and may need to be lightly shaded with whitewash for the last few weeks if the weather is very sunny. Remove cloches as soon as crop has been gathered.
Varieties. Cambridge Favourite, mid-season ; Cambridge Prizewinner, early; Cambridge Rival, early; Cambridge Vigour, mid-season; Gorella, early; Merton Herald, early; Redgauntlet, mid-season; Royal Sovereign, early; Talisman, late. Hampshire Maid, Red Rich, Sans Rivale, Gento and Triomphe are perpetual-fruiting varieties.