(Fragaria x ananassa)
The modern, large-fruited, cultivated strawberry is derived from crosses of two wild strawberry species introduced into Europe from the Americas in the 17th & 18th Centuries. In its early history it was very prone to viral disease (transmitted by Aphis), and only one of the many Victorian varieties now survives. Since the 1940’s the production of certified virus-free stock has been developed, in insect -proof houses or at altitudes where aphids cannot live. Growers can now regularly replace their plants with this healthy stock before disease affects the yield.
Wild Strawberries and the Development of the Cultivated Strawberry
About half-a-dozen wild species and subspecies have been involved in the history of strawberry cultivation in Europe.
Fragaria vesca, the wild woodland strawberry, and its subspecies F. v. semperflorens, the Alpine strawberry, are found all over Europe N. of the Alps. F. vesca reproduces by runners, but semperflorens does not produce them and spreads by seed. The fruit are tiny, but have doubtless been eaten by the human race since well before recorded history began. They were unknown to the Greeks (none grew S. of the Alps) and the Romans rarely mention them; but in N. Europe surviving records from the 11th. & 12th. Centuries indicate that they were popular in Anglo-Saxon times. Organised cultivation appears to have started in the 14th. C., and John Lydgate records strawberries being sold in the streets of London in the late 15th. C. The Victorians grew Alpine strawberries and developed named varieties, incluçling Galande and Quatre Saisons. Still grown today, the modern varieties are Baron Solemacher and Alexandria. They are propagated from seed and usually treated as annuals.
Fragaria moschata (= F. elatior), the Hautbois (or hautboy) strawberry of Central Europe across to central Russia and Turkey, has slightly larger fruit, but develops few runners. It is occasionally found naturalised in Britain. It was grown by the Victorians, whose varieties included Aromatic, Royal Hautbois and Triomphe d’Orleans; the flesh is said to have “a musky aroma”. By the 20th. C. they were little grown since they are “shy bearers” and need great care in selecting plants from which to propagate
Fragaria virginiana, the Scarlet Strawberry, is native to the E. Coast of N. America and was introduced into cultivation in Europe in the earlyl600’s. It is propagated from runners, which are freely produced. According to John Wright, writing about 1894, Old Scarlet had by then been cultivated “for two and a half centuries”; later introductions were Rosebery (1808), Scone Scarlet (1813) and Grove End Scarlet (1820). Little Scarlet still survives in some areas as a jamming strawberry.
The final introduction was the Pine strawberry, Fragaria chiloensis, which grows along the W. coasts of N.& S. America. It was first found in Chile (hence the name) and introduced into Europe about 1727, when Frezier brought it to France. F. c. grandflora, a slightly larger form from Surinam (S. America) is said to have been introduced in 1759 (Wright). Cultivated varieties include Old Pine (or Carolina) and British Queen.
After the Pine strawberry arrived in Europe, it was found to hybridise freely with the Scarlet strawberry (in their native lands they are separated by considerable distances and mountain ranges). The crosses probably first arose by chance, but soon deliberate breeding started in France, where Duchesne published his “Histoire Naturelle des Fraisiers” in 1766. Progress in France was interrupted by the Revolution towards the end of the 18th. C., and in the 19th. C. the innovators were British. These Pine x Scarlet hybrids, given the specific designation Fragaria x ananassa, form the majority of strawberry varieties grown today.
In Britain, Thomas Andrew Knight pioneered large-scale breeding, introducing Downton and Elton amongst others. Michael Keens of Islington bred Keens’ Seedling in 1821, and it is likely that this is an ancestor of most modern varieties. Thomas Laxton introduced Royal Sovereign in 1892.
John Wright, in “The Fruit Grower’s Guide” (1894) lists 14 early, 28 mid-season and 17 late varieties of large-fruited strawberries (Pines, Scarlets and Hybrids).
The 20th, Century
In the early years of the century, many of the Victorian varieties continued to be grown. Sanders (“Fruit and its Cultivation” 1926) indicated that Alpines were still popular, but the Hautbois were now little grown; he listed 9 early, 15 mid-season and 7 late varieties of large-fruited strawberries. He also describes a new race of perpetual-fruiting strawberries resulting from a cross between the Alpine and a large-fruited variety.
In the late 1940s, the techniques for raising virus -free stocks were developed and the breeding of modem hybrids was begun. The only large-fruited variety known to have survived from before World War 2 is Laxton’s Royal Sovereign; all others now grown date from after 1940. The earliest were the Cambridge series from the University Horticultural Research Station, e.g. Cambridge Late Pine; Cambridge Vigour; Cambridge Favourite. Since then, breeding has gathered pace in Britain, Europe, the Americas and Australia; there are now over 60 varieties in cultivation in Europe alone. Most stock is raised under controlled conditions and certified virus-free.
Four main groups of strawberry are of interest to the amateur grower:
Alpine: Fruit June – November. Grown from seed sown in Autumn or March; usually treated as annuals, at most fruiting for two years. e.g. Baron Solemacher, Alexandria.
Summer-Fruiting: Early, mid-season and late varieties cover the period May – July. Grown from runners planted in autumn or early spring, and replaced every 3-4 years. The Cambridge varieties are still popular; newer ones include Pegasus, Redgauntlet, Tamella, Elvira, Bounty, Elsanta, Symphony.
Perpetual (Remontant): Fruit from end of July to the early frosts. Fruit size diminishes in the second and later years, therefore best replanted every year. Some varieties produce runners; others do not and are propagated by division. Stock is not usually certified.
Varieties include: Aromel, Gento, Ostara, Rabunda, Rapella, Evita.
Day-Neutral: the newest type of strawberry, which under glass will fruit in 12 weeks from planting at any time of the year. Outdoors they behave like Perpetuals. Plants should be replaced every two years. e.g.. Selva.
To give of their best, strawberries need close attention to growing conditions and maintenance. Only a brief outline can be given here and it is recommended that more detailed sources are consulted for more information.
The cultivated strawberry is a hardy but short-lived perennial, fruiting best in the early years; therefore plants are usually replaced after 1 – 4 years depending on variety, They need a sunny but sheltered site. They will grow on any type of soil but prefer slight acidity: (pH 6.5), heavy soils must have good drainage; light, dry soils may need frequent watering.
Bed preparation before planting is important, especially when the plants will be there for 3 – 4 years; if plenty of manure/compost is applied initially, the only other feeding necessary will be with potash each February. Strawberries are very sensitive to moisture lack, and must be adequately watered under drought conditions; but if water is applied too early in the season, growth will be lush with poor fruiting. After harvest, old leaves and unwanted runners should be cut off immediately. Fruit bud initiation for the following year occurs in August.
Strawberries suffer from a number of serious pests and diseases, and should not be replanted in the same ground. New beds can follow any of the leafy crops, or other soft fruit, but not potatoes (verticillium wilt may be present in the soil).
The traditional way of growing strawberries out-of-doors is in rows (75 – 90 cm / 30 -36 in apart; plants 30 -40 cm / 12 – 15 in. apart in the rows) with straw placed between the rows under the fruit trusses as they begin to ripen. The modem version of this is black polythene; if this is used, a raised bed or ridge should be formed, so that the polythene sheet slopes away from the crown of the plants, to prevent pooling of water under the fruit. The polythene is put into place before planting, and holes about 8 cm. (3 in.) wide are cut for planting into; therefore it is essential to put trickle irrigation lines under the sheet, as otherwise watering will be inadequate.
If space is a problem, strawberries can be grown in growbags (10 plants I bag), pots, tower pots or barrels; they have also been grown in polythene tubes (15 cm./6 in. diameter, 2m. / 6 ft. long) suspended from a wall or fence. Towers can be made with flower pots of decreasing size, filled with compost; the plants are inserted round the edges, and the pots are piled on top of one another; the number of plants per pot decreases.-with pot size. Custom made, self-watering tower pots for decorative use indoors or on the patio are also available. Four old galvanised buckets, with three plants in each, standing on top of one another, have also been successful. With all of these space-saving methods, success depends on adequate feeding and watering, which need special care: deficiencies in this area are the usual cause of failure. Overwatering results in soft, rank leaf growth; underwatering will show as wilting; in either case fruit development will be poor. A high -potash liquid feed (tomato feed) should be used, to encourage fruit and restrict leaf growth; a slight nitrogen deficiency, with pale green leaves, gives the best crop.
Strawberries can be forced for early crops, in the greenhouse, cold frame or polytunnel, under cloches, or indoors on a sunny windowsill. They are self- fertile but insect -pollinated, therefore there must be either access for bees during the day, or hand pollination with a small soft brush.
Flowering starts in May and frost may affect the blossom, particularly in Northern areas; this is shown by blackened centres in the flowers. If ground frosts are forecast, it is worth covering the beds at night with hessian, fleece or newspaper (which must be removed during the day).
As soon as fruit begins to colour, netting is essential to prevent bird-damage; blackbirds especially are fond of strawberries!
Slug damage is frequent; in outdoor beds some form of slug control is needed.
Other pests include aphis, capsid, blossom weevil, seed beetle, tarsonemid mite, tortrix moth caterpillar, vine weevil, wireworm, etc.
Several diseases may occur; botrytis and powdery mildew can be controlled by careful husbandry; but crown rot, red core and verticillium wilt cannot and any affected plants should be destroyed.