Introduction
The cucumber belongs to the family of Cucurbitaceae being one of the largest families of vegetables of essentially tropical origin.
They are tender herbaceous annuals usually grown for their fruits.
Cucumber tends to be one of the most important market vegetables in the tropics and it is also the basis of an extensive picking industry.
Description
Cucumber is a trailing or climbing annual herb having some cultivars of bushy habit. It has a stout 4-angled, stiff bristled hairy stem ranging from 1-3m in length with unbranched tendrils and extensive roots that are mainly superficial.
Their leaves are triangular ovate with a rough surface to the touch.
Have bell-shaped flowers which in yellow colour. The male flowers are predominant in axillary clusters or singularly in leaf axils, while female flowers have short peduncles, as usually solitary in leaf axils.
Majority of field grown cucumber are monoecious or gynoecious and in other cases they may have hermaphrodite flowers occurring.
Cucumber has fruits which are pendulous which comes in different shapes such as blocky, oblong or elongated with varying sizes.
Their skin colour varies from pale to very dark green. The interior flesh being creamy, pale green to white.
Sex expression
Sex expression is under genetic control but usually influenced by environment and/ or chemical treatment
In most of the monoecious forms, the usual ratio of male to female flowers is heavily skewed towards maleness. Lateral shoots tend to bear a greater portion of pistillate flowers than the main stems.
Cucumber is a tri-monoecious crop that is produces 3 kinds of flowers:
- Female (pistillate) flowers which produce fruits
- Male (staminate) flowers- do not bear fruits
- Perfect (hermaphrodite) flowers which also produce fruit
Several factors affect type of flower to be produced and these include;
- High application of nitrogenous fertilizer encourages maleness
- High light intensity encourages male flowers
- Application of gibberellins (GA3) encourages male flowers.
NB: In general, any condition that leads to elongation of the nodes encourages female flowers.
Uses and nutritional value
- Flesh of fruit is eaten raw in fruit salads or as cooked vegetable
- Immature fruits (gherkins) are used in pickles
- Young leaves can be used as a salad vegetable in some parts of the world such as Malaysia.
Cultivars
Cultivars grown in Kenya include; Palomar- a variety with dark green fruit slightly pointed at the end, London Long Green- a white fleshed variety of excellent taste, Cool and Crisp- a variety bearing uniform dark green fruit, which tapers towards the end, Early Fortune, Colorado etc.
Hybrid cultivars are exclusively used for parthenocarpic cucumber production (seedless fruits).
Basic requirements
- Requires altitudes up to 1500m while others thrive well up to 1000m a.s.l
- They do best in warm climates, with an optimum range of 21-28◦C
- Soils should be well drained fertile loam soils with a pH of 6.0-7.5
- Require adequate amount of water range from 400-500m although they are intolerant to water logging.
- Light requirements. Short day, low light intensity and even low temperatures tend to promote earlier and frequent pistillate flowering while long days promote maleness.
- Seeds do germinate well at 27◦
Field establishment
Majorly, farmers do direct seeding as a means of propagation. Whereas some raise their seedlings in containers and later transplant in the main field.
A 60-70 cm square spacing is used or an interrow spacing of 100-150cm by 30-45cm within the row.
The Ministry of Agriculture (MOA) recommends a blanket application of 125g TSP/planting hole (200kg/ha) at planting time.
The seed rate for one hectare is 2.5-4.5kg which gives approximately 10000-20000 plants/ha.
Field maintenance
Irrigation- requires regular watering limiting excessive watering as it encourages fungal disease infection.
Weeding- it should be undertaken shallowly to prevent injury to the vines
Fertilization- MOA recommends top dressing with 65g of CAN/ha when plants begin to spread. When they begin to flower, apply a further 130g/plant. Liquid/ foliar fertilizer may be used as a supplement at an interval of 14 days.
Support- provide support for trailing or climbing cultivars through trellises.
Pruning- lateral shoots may be pruned after one fruit has formed
Raising of fruit off ground to prevent damage caused by dampness or pests
Pinching off- encourages branching hence more suitable on vine or trailing plants.
Harvesting.
Harvesting process begins after a period of 40-80 days from sowing.
Fresh market fruits (slicers) are usually harvested when about full size but before being fully developed. Pickles should be harvested at an earlier stage and usually when very small.
Cucumber plants grown for purpose of seed production should be ideally examined before the fruit is set and again during fruiting.
Post-harvest handling
Mature fruits should be firm, green and the size typical of the cultivar. Generally, cucumbers and gherkins are seldom stored for more than 14 days.
Short term storage should be at temperatures of 10-13◦C and a relative humidity of 95%.
Temperatures below 100c results to chilling injury leading to detoriation of the produce.
Pest and diseases
Pests
- Melon fruit fly
- Melon ladybird
- Cotton aphid
- Tobacco whitefly
- Stink bugs
Diseases
Majorly include powdery mildew, downy mildew, anthracnose, stem rot, bacterial wilt, cucumber mosaic etc.
