Propagation
Propagation is from seed.Planting Method
Leeks can be direct seeded into the field or can be sowed into seedling trays and raised in greenhouses. When the seedlings are about 15 cm tall after about 6 weeks, they are planted out into the fields.
Most commercial growers are opting for the planting of seedlings as this gives better surety of crop volume per hectare and crops are harvested sooner and are more uniformly. Leek planting by hand is a labour intensive practice and therefore expensive. Both direct seeding and planting of seedlings can be done mechanically.
To get the best and longest white blanched shanks or stems it is best to draw planting furrows of 15 cm deep and plant the seedling in the bottom of this trench and cover the roots and lower stem after planting. Four weeks later once the plants have established the soil can be hilled up to further cover the stem.
The ideal length of the blanched or white part of the stem is 15 cm to 20 cm. When practising direct seeding, weed control is a considerable challenge during the initial stages of growth. For this reason, the planting of leek seedlings is more popular with commercial growers as this allows for more effective weed control prior to planting.
Spacing
Plants can be spaced 15 cm apart in rows that are 30 cm or 50 cm apart with slightly wider rows left for tractor and implement traffic if required.
This should provide a stand of about 120 000 to 200 000 leek plants per hectare. Baby leeks are planted closer together because their growing season is shorter and weeds are less likely to become a problem.
Sowing Time
Sowing of leek seeds in seed trays is done between six and eight weeks before the intended seedling planting time. In South Africa, the two popular sowing times for leeks are early autumn, from early March to early April, and then again during late winter in July and August.Planting Time
Leek seedlings are planted out in April and May and again in late August and September.Growth Period
Direct seeded leeks take six months to be ready for harvest. So if the seeds are planted in early March they are ready to harvest in August or September. If a well-raised seedling is planted in mid-April or early May it can be ready to harvest by late July or early August.
The planting of leek seedlings rather than seed sowing saves a month of crop management time and money. Young tender leeks are harvested much quicker at eight to ten weeks after planting of seedlings.
Fertilization
As mentioned in soil preparation it is strongly advisable to take a soil sample and source professional recommendations to ensure the correct nutrient applications for the particular intended growing area.
The following recommendation is a norm that can be followed when fertilizing leeks. In the week prior to planting the seedlings, apply 250 to 300 kg of 2:3:4 (30) per hectare when preparing the plant bed and disc into the top 20 cm of soil.
This provides nutrients immediately after planting the leek seedlings and will provide the plant with energy for a good start and also to assist with the stress created during the transplant process. If sowing leek seeds, apply the first fertiliser application along the plant row as soon as the new plants start to surface.
Two to three weeks later, broadcast (spread) the same as the first application along the plant rows. After a further two to three weeks, a third application of 250 kg per hectare of LAN (28) can be broadcast along the plant rows.
This should be ample for the crop to reach maturity and be ready for harvest. Remember to practice weed control as weeds will rob the plant of the supplied nutrients.