Strawberry
- Fragaria X ananassa
The cultivated strawberry, Fragaria X ananassa Duch., is a
member of the Rosaceae,
subfamily Rosoideae, along
with blackberries and raspberries.
Cultivars
Two main types
of cultivars are recognized based on environmental control of flowering:
Short-day or June
bearing. These require photoperiods
under 14 hr and/or temperatures under 60°F for floral initiation.
As the name suggests, they generally bear fruit in the spring only,
unless grown in areas with cool summer temperatures such as coastal California.
Everbearing.
These cultivars fruit throughout the growing season provided
temperatures are not too high. There are two types of everbearers:
Long-day.
Lengthening days promote more-or-less continuous flowering throughout
the summer, provided temperature is not too high.
Day-neutrals.
Photoperiod has no effect on flowering. Also will flower several times
per year, but would do so in short as well as long days.
Temperature may interact or override the
photoperiodic effect in all types of strawberries. Basically, cool
temperatures promote and warm temperatures inhibit flowering. The
short-day types dominate the industry, but day-neutrals are increasing
in importance
in the USAMajor
California cultivars in 2002 were ‘Camarosa' (40% of acreage),
‘Diamante‘ (25%), ‘Aromas' (2.5%), and ‘Selva' (2%). Florida, the #2
state, also grows ‘Camarosa' and ‘Selva', and ‘Oso Grande', ‘Sweet
Charlie', and ‘Rosa Linda'.
ORIGIN, HISTORY OF CULTIVATION
Prior to the relatively recent development of F. X ananassa, wood strawberries (F. vesca) and Musky strawberries (F. moschata,) were cultivated in
Europe and Russia for centuries. These species were largely supplanted by cultivation of F. X ananassa over the last 250
years. In the early 1700s, inter-planting of F. virginiana (male) with F. chiloensis (female) in France led to production of hybrid seedlings that came to be
known as Pineapple or Pine strawberries, progenitors of the modern
cultivated strawberry, Fragaria X ananassa Duch. Native American strawberries were enjoyed by early
settlers in the eastern USA, and in the early 1800s, F. X ananassa cultivars were
brought to America from Europe. Plants selected in Pajaro, California became the basis of the California industry sited near
Watsonville, the main strawberry region in California.
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World (2004 FAO) - 3,113,840
MT or 6.9 billion pounds. Strawberries are produced in 73 countries
worldwide on 529,000 acres. Average yields are 13,000 lbs/acre.
Top 10 Countries
(% of world production) |
| 1. USA (27%) |
6. Italy (5%) |
2. Spain (9%)
|
7. Russia (5%) |
3. Japan (7%)
|
8. Turkey (5%) |
| 4. Korea, Rep of (7%) |
9. Poland (4%) |
5. Mexico (5%)
|
10. Germany (3%) |
United States (2004 USDA) -
1,066,227 MT or 2.2 billion lbs. The industry value
is $1.47 billion, and prices
paid to growers are 66 ¢/lb for fresh, 28 ¢/lb for
processed. Yields avaerage over 42,000 lb/acre. Leading
states:California (86%), Florida (9%).
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Plant
Strawberries are perennial, stoloniferous herbs,
meaning that they spread via stolons or "runners". The
leaves are trifoliate and arise from the "crown" (a reduced stem
in the center of the plant). Leaflets are ovate or broadly oval,
obtuse, dentate or coarsely serrate. The runners produce "daughter"
plants at every other node.
Flowers
Flowers are white, about 1" across, with 25-30
yellow stamens and 50-500 pistils on a raised, yellow, conical
receptacle. Borne on a dichasial cyme, the center-most terminal flower
opens first and is largest, producing the largest fruit.
Pollination
Most cultivars are self-fruitful and therefore do
not need cross pollination for fruit set. However, bee activity is
beneficial in transferring pollen to stigmas in an individual flower.
Fruit
The strawberry is an accessory fruit, since
the
edible portion is non-ovarian in origin (it is largely swollen
receptacle tissue). The true fruits which contain the seed of the
strawberry are achenes, which are similar to tiny sunflower seeds. The
achenes are the numerous, tiny, ellipsoid specks that cover the fruit
surface. Fruit mature rapidly; ripening occurs in 20 to 50
days after pollination.
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Soils and Climate
Sandy to loamy soils with good drainage and pH of
5-7 are best for strawberries. Depth is not important in most
cultural systems, since plants are often grown for only 1-4 years, and
develop only shallow root systems. Strawberries are most often grown on
6-10" raised beds to improve drainage. Soil fumigation is regularly practiced for
strawberries, since several soil-borne diseases and nematodes are
problems. For this reason, sandy, light soils are best. Methyl bromide has been used for
fumigation, and its ban in 2005 triggered the filing of critical use exemptions by the US government on behalf of the industry.
Strawberries have a cool temperate climate
preference. Strawberries do so well in central
Florida in winter, and in coastal California from spring to fall.
However, they are sensitive to winter freezing. Crowns are killed at
10-20°F. Strawberries have
low chilling requirements to break dormancy, <500 hr at or below
45°F in many cases.
Propagation
Propagation is
by division of daughter plants.
Rootstocks
- None
Planting Design,
Training, Pruning
Planting systems fall into 2 main categories: matted
row and annual hill systems. Annual hill systems are typical of
commercial production, and are fruited once and renovated, and usually
intensively managed under "plasticulture". Matted row systems are more
typical of home gardens and processing operations, and are cropped for
up to 4 years, then renovated. Whether matted row or hill
system, strawberries are typically planted on beds 6-10 inches high to
improve drainage around roots and provide discrete row middles for
cultural practices and picking.
The two methods of strawberry culture: annual hill (top 2
photos) and matted row (bottom 2 photos). Plastic mulch in the annual
hill system prevents weeds, keeps berries clean, and warms the soil in
late winter, which forces plants into early growth. Top left, a double
row bed system in January after fall establishment of plants. Top
right, looking perpendicular to rows in May during peak production.
Bottom left, a matted row planting of ‘Totem' strawberries used for
processing in Oregon. The grower obtains 3-4 years of production, then
renovates the site. Bottom right, a matted row bed in a backyard garden.
HARVEST, POSTHARVEST HANDLING
Maturity
Strawberries are ripe when red color covers the
fruit.
Harvest Method,
Postharvest Handling
Strawberries are harvested by hand, whether for
fresh market or processing. For fresh market, caps (calyx) are left
intact; for processing, fruit are plugged (caps removed).
Storage
Strawberries are extremely perishable, having a max
storage life of only 5-7 days at 32 F and 95 % RH. They are
either processed or shipped immediately.
About 75% of the strawberries grown in the USA are
sold fresh, and 25% processed (mostly frozen). Strawberries are higher
in vitamin C than many citrus fruits. Per capita consumption of
strawberries was 7 lbs/year in 2004.
Nutritional composition (per 100 gram edible portion):
|
Strawberry |
| Water (%) |
90
|
| Calories |
37
|
| Protein (%) |
1.4
|
| Fat (%) |
0.7
|
| Carbohydrates (%) |
8
|
| Crude fiber (%) |
1.5
|
|
%
of US RDA* |
| Vitamin A |
1.2
|
Thiamin, B1
|
2.1
|
| Riboflavin, B2 |
4.4
|
| Niacin |
3.3
|
| Vitamin C |
131
|
| Calcium |
2.6
|
| Phosphorus |
2.6
|
Iron
|
10
|
| Sodium |
<1 |
Potassium
|
3.5
|
* Percent of recommended daily allowance set by FDA, assuming a
154 lb male adult, 2700 calories per day.
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