Leek (Allium porrum) is a vegetable in the same family with onion and garlic.
Its white elongated bulb at the base of the leaves also make a very tasty, fresh vegetable, either on its own or in stews or casseroles while the green leafy tops of leek is excellent for flavouring soups and stews.
Leeks are good sources of Vitamins A, B6, C and K as well as calcium, manganese and magnesium and therefore help fight infections, have anti-cancer properties among other benefits.
Leeks can be grown both in greenhouses (indoors) and in open fields.
They do well in well-drained, rich soils with high organic matter and an optimum pH of 6.2-6.8.
An optimum temperature of 12-25 degrees centigrade is essential.
They also require as much sunshine.
Propagation is by seeds, which are first raised in a seedbed.
- Choose a weed-free, well-drained location, where no onion family crop has been cultivated for at least 1-2 years.
- Construct raised beds, about 1 meter wide.
- Drench soil with a mixture of LOYALTY 700WDG 10g + PYRAMID 700WP 100g+ OPTIMIZER 20ml in 20 litres of water. This helps to eradicate soil pests and diseases, break seed dormancy and promote uniform germination.
- Form shallow furrows.
- Sow seeds, about 2.0cm apart and cover lightly with soil.
- Mulch and water the bed.
Seeds germinate within 1-2weeks after sowing.
The seedlings are ready for transplanting when they are at least 6 to 12 inches tall and transplanting should be done early in the morning from 6-10am or late evening 4-6pm (cool hours of the day.
Prior to transplanting, the nursery bed should be watered to saturation in order to avoid damaging the seedlings while getting the seedlings.
Seedlings are pulled from the wet nursery bed and transplanted in the main field, 15cm deep at a spacing of holes about, 10cm apart and 20cm between the rows.
- Seedlings’ roots should be trimmed to about 5cm long and the tips chopped off while transplanting.
- To overcome transplanting shock, seedlings should be sprayed with OPTIMIZER 10ml/20l
Irrigation– leeks have shallow root systems and need consistent moisture. Regular watering should be done, especially if the weather is dry.
Mulching- this helps in retention of moisture and suppression of weeds. Decomposed mulch releases nutrients into the soil which are absorbed by the crop.
Weeding-weeds compete with the crop for nutrients, water, sunlight and space. They also harbour pathogens.
Leeks are poor competitors with weeds and therefore the garden should be kept weed free in order to avoid the losses attributed to weed infestation.
Blanching- this entails adding soil to the trench around the stems, which helps to keep the area dark by keeping out the sunlight. Planting leeks in deep holes helps in getting blanched stems.
PESTS & DISEASE MANAGEMENT
Cutworms– these are brown or black caterpillars which live in the soil. They cut and eat the stems of young seedlings and trans-plants. Heavy infestations can cause total crop loss.
Drench soil with PROFILE 440EC 60ml/20l or PENTAGON 50EC 20ml/20l
Onion fly– the adult fly looks like a small grey house fly. The maggots/larvae, which are creamish white maggots feed on the lateral roots, then tunnel into the taproot and sometimes bore into the base of the stem. Infested leaves turn bluish and eventually wilt. The plant becomes shriveled and dies. The maggots are also found inside developing onion bulbs. Their feeding exposes the plant to infection by diseases like soft rot.
Spray KINGCODE ELITE 50EC 10ml/20l or LEXUS 247SC 8ml/20l or PRESENTO 200SP 5g/20l
Onion thrips– these are the major insect pest of leeks which cause white flecking on the leaf surface and a drastic reduction in foliage quality as they feed.
Spray ALONZE 50EC 5ml/20l or PROFILE 440EC 30ml/20l or DEFENDER 25EC 40ml/20l
Leek moth– the young, pale green caterpillars tunnel through the leaves to feed, which are disfigured with whitish brown streaks. As more and more tunnels are made, the leeks lose their strength and may collapse and die. Older caterpillars tunnel down into the stem of the leek causing extensive damage, which may cause the leek to collapse or rot from within.
Spray SINOPHATE 750SP 20g/20l or KINGCODE ELITE 50EC 10ml/20l or PRESENTO 200SP 5g/20l
Damping off– this is a soil borne disease which attacks the seeds and seedlings. Infected seedlings may fall over and die due to breakdown of plant tissues at the soil level, while the attacked seeds do not emerge.
Spray CHANCETYL ELITE 800WDG 50g/20l or MILLIONAIRE 690WDG 40g/20l or drench PYRAMID 700WP100g/20l
Downy mildew-the infected leaves turn pale-green, then yellow, and collapse and eventually die. The pale-green and yellow stage is characterized by oval-shaped lesions that often become infected with other diseases. This disease is favored by cool and humid weather.
Spray GEARLOCK TURBO 250WP 25g/20l or FORTRESS GOLD 720WP 40g/20l or TRINITY GOLD 452WP 50g/20l
Purple blotch– infection causes formation of small water soaked lesions with whitish centres, mostly on the older leaves. These lesions enlarge as infection progresses and become purplish with light yellow concentric rings on the margins. Leaves may turn yellowish-brown, lose erectness and eventually wilt, if the disease is not controlled.
Spray COLONIZER 440WP 50g/20l or ABSOLUTE 375SC 10ml/20l or TRINITY GOLD 425WP 50g/20l
White rot– infection is most noticeable in hot, dry conditions and plants grown in overcrowded conditions are more vulnerable. The infected leeks have yellow leaves, with a white or grey fungus covering the underground base of the plant, looking like strands of white thread.
Spray MILLIONAIRE 690WDG 40g/20l or RIMETA GOLD 300SC 40ml/20l or EXEMPO CURVE 250SC 15ml/20l
Leek rust– leeks growing in wet soil which is rich in nitrogen but lacks potassium are particularly vulnerable. The symptoms of leek rust are orange, powdery spots on older leaves, which later turn yellow.
Spray MILESTONE 250SC 10ml/20l or MILLIONAIRE 690WDG 40g/20l or COLONIZER 440WP 50g/20l
Botrytis leaf blight– symptoms on the leaves initially appear as greyish-white, oval-shaped spots which are usually surrounded by a silvery white halo with uneven margins. The centres of most of the spots become sunken and straw- colored. In severe cases, tips of the leaves begin to dieback.
Spray EXEMPO CURVE 250SC 15ml/20l or IPRODE 500SC 10ml/20l or EXPLORER 3SL 10ml/20l
NUTRITION & NUTRITIONAL DEFICIENCIES
Leeks perform best with a steady supply of nutrients.
These nutrient elements include both macro and micro elements, and to achieve this balanced nutrition, application of both basal and foliar fertilizers is highly recommended.
Basal fertilizers are absorbed by the crop through the roots, and include DAP, CAN, NPK, UREA, among others. Mixing the fertilizers with HUMIPOWER at the rate of 50:1 helps in improving the nutrient uptake by the plants as well stimulating growth, among other benefits.
Foliar fertilizers are best absorbed through the foliage. They supply both macro and micro nutrient elements and include OPTIMIZER, LAVENDER, GOLDCHANCE SERIES, LEGENDARY, PORTEGE GOLD, LAVENDER, among others.
Fertilizer application should be done at the recommended rate and in good time for best results.
Nutrient deficiency expression symptoms vary for acute or chronic deficiency conditions.
The older leaves gradually change from their normal characteristic green appearance to a much paler green colour. As the deficiency progresses these older leaves become uniformly chlorotic. The young leaves maintain a green but paler color and tend to become smaller in size.
Correction; use GOLDCHANCE SUPER GROWTH 50g/20l or LAVENDER 20ml/20l
A major visual symptom is that the crops are dwarfed or stunted. A distinct purpling of the stem, petiole and the under sides of the leaves may occur. Under severe deficiency conditions leaves develop a blue-gray luster and a brown netted veining of the leaves may develop.
Correction; use GOLDCHANCE SUPER START 50g/20l or LAVENDER 20ml/20l or PLANT SOUL 20ml/20l or LEGENDARY 40ml/20l or DIMIPHITE 10ml/20l or GREENPHITE 40ml/20l
Some leaves show marginal necrosis and/ or tip burn, while others at a more advanced deficiency status show necrosis in the interveinal spaces between the main veins along with interveinal chlorosis.
Correction; use GOLDCHANCE SUPER FLOWERS & FRUITS 50g/20l or DIMIPHITE 10ml/20l or GREENPHITE40ml/20l or LEGENDARY 40ml/20l
Copper-deficient leaves are curled, and their petioles bend downward. Deficiency may also be expressed as a light overall chlorosis along with the permanent loss of turgor in the young leaves. Recently matured leaves show netted, green veining with areas bleaching to a whitish gray. Some leaves develop sunken necrotic spots and have a tendency to bend downward.
Correction; use BIO DISTINCTION 50ml/20l or COLISEUM 20ml/20l
In the early stages of zinc deficiency, the younger leaves become yellow and pitting develops in the interveinal upper surfaces of the mature leaves. As the deficiency progress these symptoms develop into an intense interveinal necrosis but the main veins remain green.
Correction; use ZINC GOLD 10ml/20l
- When doing foliar spray, it is advisable to mix the product (insecticide, fungicide, foliar feed or herbicide) with INTEGRA 3ml/20l. This is a sticker, spreader, wetter and penetrant, which improves the efficacy of the product(s).
- Alternation of chemicals (especially fungicides and insecticides) throughout a crop’s season help in preventing resistance build-up by the pest.
- Post-harvest interval (PHI) of chemicals should be observed accordingly.
- All basal fertilizers and manures should be mixed with HUMIPOWER, which is an excellent soil amendment and fertilizer blend.
MATURITY, HARVEST & POST-HARVEST HANDLING
Leeks are easy to harvest and are best enjoyed when fresh.
Leek harvesting can begin about 80 days after planting and continue until the harvest is complete, or the weather makes further harvest unfeasible.
Harvesting can be prolonged by only picking only the needed leeks and allowing the rest to continue growing. The unharvested leeks grow larger and more flavorful.
Usually, leeks can be harvested when they reach about the size of a finger or pencil or until they reached their mature size.
Harvested leeks should be placed in boxes or containers that allow free circulation of air inside, and the boxes or containers should not be overloaded.
Precooling is an important step immediately after harvesting. This involves bringing the crop to about two degrees centigrade as soon as possible and keeping it at this temperature and at a relative humidity as close to 100% as possible. Under these conditions they can be stored for between 2 to 3 months.
A low temperature delays leaf sheath elongation and its curvature, both being factors that affect quality. It also causes a loss in the intensity of the green colour, which is another sign of freshness.
Leeks do not produce ethylene but are moderately sensitive to this gas, which can hasten softening and the appearance of diseases.
Transportation must be carried out at relatively low temperatures. The levels of moisture must be high while direct light and piling must be avoided.