Organic Cucumber - Poly House Cultivation
Growing Organic Cucumbers in Protected Cultivation
-Continental cucumbers are 30 to 45 cm long, dark green, smooth skin slightly ribbed, and glossy.
Lebanese or mini cucumbers are 14 to 20 cm long, green and glossy. They are quicker to
harvest from flowering, with less bent fruit, especially in winter.
Varieties may vary with yields and quality, tolerance to powdery mildew and cold tolerance.
-There are distinct warm season and cold-season varieties.
Greenhouse conditions -
A polythene greenhouse should be selected with plenty of light and ventilation and preferably sited so that plants are grown in north-south facing rows. The height of the greenhouse to
the gutters should preferably be over 4 m.
A relative humidity of 85% is optimum. Use a hygrometer to check the relative humidities. High humidities increase leaf diseases such as botrytis and powdery mildew, and the plants
can also be too busy. Ventilation may be adjust the vents to maintain optimum temperatures and humidities, especially in the afternoon. This will reduce diseases such as botrytis and increase the uptake of nutrients. Do not over-ventilate as this may reduce the relative humidity to a low level. This can reduce yields and fruit can have gummy ends. Fans can also be used for cooling and ventilation. Ensure that misters, if used, do not increase the relative humidities too high.
Cucumbers need light levels of about 50,000 lux. On clear days in summer, light levels are often above 100,000 lux and temperatures are too high. A thermal blanket over the crop can
be used to automatically shade the plants at a selected temperature i.e. 32 °C.in hot weather and decrease day temperatures. If there is no thermal blanket, in the warmer months,
It is preferable to maintain the temperature above 14°C in winter
Optimum temperatures are 22 to 34ºC. Temperatures over 40 C or less than 14°C are unfavorable to cucumber production. The absolute minimum temperature is 5 C.
Seed into sterilised, individually celled plastic seedling trays filled with fresh sterilised potting mix. Cover seeds with 5 to 10 mm of vermiculite or perlite. Seed may also be planted into
peat blocks, 4 to 5 cm jiffy pots, or 4 to 8 cm rockwool blocks for 2 to 6 weeks before planting into the greenhouse. Plants can be transplanted at the 2 to4 leaf stage. The rockwool blocks
are placed directly on top of the slabs. Some growers may seed directly into bags in summer and transplant in winter.
Low temperatures give slow and uneven germination and plants of poor vigour.
The optimum temperature for germination of cucumber seed is 27 °C, day and night.
Plant at 1.5 (winter) to 2.0 (summer) plants per square metre, with plants at 40 to 60 cm
apart, with double rows on 2 m centres. Lebanese cucumbers can be planted slightly closer
(up to 3 to 4 plants per square metre) than Continental cucumbers. Yields will decrease if too
many plants are grown, due to insufficient light and a build-up of diseases..
Cropping schedules -
-The best cropping periods for greenhouse cucumbers are from August to November and from April to May.
-Summer cropping is difficult if high temperatures occur in the greenhouse.
-Greenhouse cucumbers can crop for 12 months when properly managed, but the normal picking period is much shorter. Growers often have three crops per year.
Irrigation/nutrient solution -
Use organic fertilizers, micronutrients & PGR(Plant Growth Regulators) for nutrients supply through irrigation.
Training, pruning and thinning -
Remove the side shoots and tendrils on the main stem.
Thin to one fruit per two nodes for the Continental varieties, especially curled fruits
which may be visible after a few days. The fruits may not be thinned alternately, as reject fruit are removed first. Some fruits will drop off naturally. Do not thin the Lebanese varieties, which may have more than one fruit on every node and up to 4 to 7
fruit per node. Tendrils may need to be removed if these wrap around the fruits.
Place the plant over a hoop, or pipe, or plastic saddle at the top of the wire.
Stop the plant by removing the growing point at the fourth leaf over the wire. Allow two laterals to grow. These will grow downwards. Stop growth just before they reach the ground.
As plants mature, old or diseased leaves can be gradually removed, especially to allow better light into the plant.
Symptoms on leaves begin as small dark water spots which enlarge and become light brown
and finally a pale bleached colour. The larger lesions are restricted by the leaf veins giving
an angular appearance to them. Old lesions frequently become tattered and holes develop
on the leaf. Yellow haloes may be seen around the lesions.
Fruit lesions are often slightly raised and corky and may produce a white crusty deposits.
Under high humidity, there is often a bacterial gum exudate from the scabs.
Lesions caused by this disease do not contain the black fruiting bodies characteristic of gummy stem blight.
The bacteria are spread in water and are more common under overhead irrigation. It is worse in areas with high relative humidities.
2:Gummy stem blight fungus (Didymella bryoniae or Mycosphaerella cucumis)
Crops that are planted too close are often affected by Sclerotinia disease. This fungus causes a watery rot, usually at the base of the stem. Plants wilt. Reduce plant density and increase ventilation.
Alternaria, Fusarium oxysporum and Xanthomonas (bacterial spot) diseases occasionally occur.
Use Certified Organic Inputs for control this type of diseases.
Cucumbers under protected cultivation produce fruit without pollination. However, pollination can take place from nearby field cucumbers which are monoecious (they have both male and
female flowers). If flowers are pollinated, seeds form in the fruit and the fruit becomes bulbed, bitter and unsaleable.
The time from seeding to harvesting can be 4 to 6 weeks in summer and 11 weeks in winter.
In summer, fruit are ready for harvesting two weeks after flowering for the long varieties and 7 to 10 days after flowering for the Lebanese varieties. Pick fruit in early morning. Cut fruit so that 1 to 2 cm of stalk remains at the end of the fruit.
Continental varieties may need picking every two days and Lebanese varieties may need daily picking.
Cucumbers should be handled carefully as they are easily marked.
There are normally three crops per year in the same area, but sometimes there are two crops
per year, or one crop may be harvested in the warmer months for up to 8 months. Fruit are
more plentiful and larger in summer. Pick for 10 to 15 weeks with 20 to 25 fruit in summer and 10 fruit in winter. Long term crops in the warmer months may produce 30 to 40 fruit per plant. The average weight for Continental cucumbers is 500 to 600 g, but may weigh up to1.4 kg. Average yields are about 500 to 550 t/ha/a, with about 80 to 90 fruit per square metre per year. Yields of Lebanese cucumbers may be higher than Continental cucumbers. Fruit may average 100 g each.
Good quality fruits should be dark green, and be firm, with good, crisp flavour.
Reject bent fruit and marked fruit. Wipe off sand and dust of Continental fruit. Wash
Lebanese fruit and dip in a calcium hypochlorite solution which contains 2 ppm chlorine to
prevent fruit breakdown. Remove old flower parts at the end of the fruit. Fruit are packed .