Strawberry

Appetizing strawberry. Isolated on a white background.
Common Name
Strawberry

Scientific Name
Fragaria x ananassa – fragola coltivata
Fragaria vesca – fragola di bosco

Botanical family
Rosaceae

History and Origins

Fossil traces were found of wild strawberry dating back to the Neolithic and interglacial period. In Roman times, the strawberry was known for its delicate fragrance as the Fragum, from the verb fragare, to smell good, to perfume (the Latin word seems to derive from the Sanskrit root GHRA, “fragrance”). This was referring to the wild strawberry, Fragaria vesca (vesca seems to come from vescor: to eat, to taste).
The cultivated strawberry originates instead from the crossing of species from America (Fragaria virginiana and F. chiloensis) which began to arrive in Europe soon after the discovery of the New Continent.
Fragaria virginiana (originally from Virginia in North America, with large fruits and sunken achenes) seems to have arrived in Britain and then was brought to France.
In 1712, Frézier, a French officer, returning from an expedition in Chile, reported that plants of Fragaria chiloensis (with large fruits and superficial achenes) did not produce pollen and were fertilized using Fragaria virginiana. This was how the first hybrids were born and from which arose today’s strawberries that delight our tables.
The current scientific name of the cultivated strawberry Fragaria x ananassa (the international botanical nomenclature requires hybrids to be indicated with a multiplication sign between the name of the genus and the species.
Fragaria x ananassa strawberry was classified by the botanist Duchesne in 1766 due to the similarity of the fruit with pineapple, both in form as well as taste).

Nutritional characteristics

Strawberries contain 90% water and have a low energy content (containing only 30 kcal / 100 g). They contain about 5% of soluble sugars and have a high content of potassium, calcium and vitamin C.
Strawberries also contain folic acid (important in the prevention of certain birth defects), ellagic acid (this has a protective effect against certain cancers especially esophageal), fiber and pectin. It is also rich in polyphenols (antioxidants).

Diffusion and importance

Italy is one of the world’s leading producers of strawberries (after the USA, Poland, Spain and Japan), grown mainly in a protected environment (greenhouses and tunnels) both in the south and in the north of the country.
The amount of cultivation in open field comes to nearly 4,000 ha (of which 17% in Sicily and 16% in Emilia Romagna) while those grown under cover is about 8000 ha (of which 75% in Campania).

Botanical characteristics

It belongs to the Rosaceae family, consists of many species and hybrids, and is widespread in the world in all temperate and tropical zones.
– Garden strawberry Fragaria x ananassa (a hybrid formed between Fragaria virginiana and F. chiloensis)

Garden strawberry, fragaria x ananassa
Garden strawberry

– Wild strawberry Fragaria vesca (other wild species F. viridis, F. moschata)

Wild strawberry, fragaria vesca L.
Wild strawberry

The strawberry is a perennial herbaceous plant, equipped with stolons (creeping stems).

Strawberry plant
Strawberry plant

It has a bunched root system that is made up of primary and secondary roots that originate directly from the base of the stem (root collar) at the base of each leaf. The roots are very superficial.

The stem (also called clump or crown) is very short (2-3 cm), epigeous; when the plant is young, its texture is herbaceous; as it gets older it tends to grow stronger and become slightly woody.

Its leaves, borne on petioles of varying length, are generally composed of three leaflets that have serrated edges (dentate), characteristic for each variety, all placed on the same level and fanned (palmate leaves). Axils of the leaves form vegetative and reproductive buds from which originate other heads, stolons or inflorescences.

The flowers are white, generally hermaphrodite, long stalked, bearing branched inflorescences.

fiore fragola
Fiore della fragola

The fruit is actually a “false fruit” since it is made by the enlargement of the receptacle, while the real fruits are green, yellow or red achenes (called seeds), which are inserted in the surface of the epidermis. The shape of the fruit varies depending on the variety (conical, conical-elongated, conical-rounded, heart-shaped etc.). The color may vary from orange, to bright red, to dark red.

Strawberry fruit
Strawberry fruit

Climate and soil requirements

Strawberries have a great capacity to adapt to different environments.
During winter dormancy, they have a great resistance to cold. A certain period of winter cold is necessary to switch to the reproductive stage (though variable depending on the variety). The cold requirements may be satisfied before or after planting or even from the refrigerator-conservation of seedlings that are used for planting. Cultivars adapted to southern areas generally have lesser cold requirements. The minimum temperature for growth is around 5° C, the optimal 18-22° C during the day and 10-13° C at night.
As temperature and brightness lower, and daylight hours reduce, the plant enters into dormancy
In Italy, after fruiting, there is the maximum growth and elongation of the stolons; the production of stolons competes with the growth of other parts of the plant and with the production of fruit. If the stolons are allowed to grow undisturbed, in the season that follows the mother plant will have a lower production and smaller fruits.
The photoperiod plays an important role in the process of fruiting and the formation of stolons. For fruiting, the cultivars can be short-day, long-day and day-neutral.
Short-day cultivars bloom once in the spring and the buds differentiate in autumn when the temperature lowers. Generally the sterile buds (non-differentiated) evolve to flowers after the plant has been subjected to short days and lower temperatures of 20-22° C for about a month; the longer the period of short days with suitable temperatures, the greater the production. With rising temperatures in spring, the buds that were differentiated in autumn swell and emit inflorescences.
Long-day remontant cultivars form flower buds during the summer.
Day-neutral remontant cultivars are indifferent to the length of the day and continue to flourish until the temperature drops and stops vegetative activity.
Pollination may be both anemophilous and entomophilous.
Soil
Strawberries prefer soil that is sub-acidic (pH 5.5-6.5 but tolerates a pH of up to 7.5 in good agricultural land), loose and with a high content of organic matter, but it is possible to get excellent results in almost any type of soil if it is well worked and prepared. It is easily subject to iron chlorosis.
Water is needed in moderate amounts but consistently throughout the growing cycle (strawberries have an inefficient shallow root system). Higher water needs are required during the post-transplant phase and during the production of the fruit. Strawberries do not like being waterlogged.

Varieties

Strawberries are grouped in two varieties: June-bearing and remontant
June-bearing variety: A large majority of varieties grown in the world are part of this group. Depending on the latitude, they bloom in the spring and produce for about 20 days. If you move south, the production period is extended up to 60-90 days.
Remontant variety: This variety is also known as re-bloom “day-neutral”, that is because, unlike the June-bearing variety, they are not sensitive to the photoperiod. The photoperiod influences the budding period of the strawberry flowers. The remontant variety, in normal temperatures, emits flowers continuously throughout the year. This means that production can be spread over time and not just seasonally like with the June-bearing variety. Remontant varieties when grown, for example, in the heated greenhouse or at home, produce fruit even in winter, the season when you cannot produce strawberries if the plants are grown outside (e.g., professional systems, vegetable gardens, terraces). Production starts around 90 days after planting.

Fundamentals of cultivation practices

Planting
Le June-bearing varieties are usually planted in summer (July-August) using refrigerator-conserved plants (uprooted in winter, in full dormancy, cleaned, sorted, calibrated and stored in a refrigerator at -1 / -2° C) or “fresh or vegetating” plants.
The remontant varieties may be planted at any time of year.
It is preferable to plant strawberries on raised rows that favor water drainage to prevent waterlogging.
It is advisable to mulch the strawberries with black plastic film that impedes the growth of weeds, reduces fruit rot, ensures greater cleanliness as there is less contact with the soil, and promotes heating of the soil for an earlier ripening. Perforated plastic film is generally used, double rowed, distances between the rows of 0.30 to 0.35 and a distance of 0.25 to 0.35 m within the row. The raised rows are generally spaced 1.20 m apart (from center to center) with a passage of 0.50 to 0.60 m (a density of 4-5 plants per m2).
Fertilization
The application of organic matter and fertilizers must be carefully evaluated according to the fertility and natural content of the soil, the needs of the variety and the type of cultivation. Strawberries benefit from manure and potassium fertilization (they improve the quality of the fruit). Nitrogen is important especially in the period after planting to promote optimum vegetative growth and good flower production. Avoid excess nitrogen during the spring growth period as it reduces the quality of the strawberries (less flavor, texture and sugar content, increased susceptibility to rot).
Cultural practices
To improve the quality of the plant, removal of the first flowers is recommended. This allows the plant to strengthen and to have a more abundant production.
In autumn the plants put out stolons, which should be removed manually as they negatively affect productivity.
During the spring vegetative growth, manually remove the leaves (leave only the most active and green) to reduce any outbreak of fungal infections and overwintering insects and mites on the foliage.

Harvesting

Strawberries are harvested during the following periods:
– From mid-February to mid-May for protected crops depending on latitude;
– From mid-April until mid-June for open-air crops;
– In the autumn for the off-season productions obtained with refrigerated plants of June-bearing variety;
– From spring to autumn with remontant varieties.
The strawberries must be collected with the calyx and the peduncle still attached to the fruit; they must be hard and uniformly red. If there is white or light green, it means that they are still unripe; but if they are dark red, it means that they are too mature.