The following cultural instructions are for maincrop leeks.
Should one be considering growing for exhibition, then the instructions would be quite different.
For example, sowing dates could be ten weeks or more earlier, plus the need for heating and lighting would increase, and potting on would be proportionally earlier.
Subject to variety maincrop leeks will grow to around 600mm (24") high with a spread of around 300mm (12")
Summer varieties will take around 30 weeks to mature from the sowing date.
Winter varieties can be left in the ground to be harvested as required during the winter months.
Typical Growing Season
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Sow seed in trays or cell trays of seed compost and germinate at temperature of 13°C (55°F)
Alternatively sow one or two seeds in each module of a cell tray.
Germination should take 7-10 days
Prepare trenches now if not done earlier.
Take out a trench 300mm (12") wide, and 600mm (24") deep, placing the bottom layer on one side of the trench and the topsoil on the other.
Fork soil at the bottom 150mm (6") deep and spread a layer of well rotted manure or garden compost.
Break up subsoil as you return it, mixing with it, a bucketful of farmyard manure to each metre (3ft) run and 50gms(2oz) of bonemeal.
Similarly when returning top soil, mix in well rotted manure, and add 30gms (1oz) of bonemeal per metre run.
Rake bed over thoroughly in each direction, but don't do this if the surface sticky.
Prick out seedlings if large enough to handle into 7cm (3") pots of potting compost and grow on at a temperature of 10°C (50°F)
Keep them in good light but not direct sunshine.
Gradually harden off seedlings by placing in a cold frame until they are of sufficient size to plant out.
Leeks are ready for transplanting when they are about 200mm (8”) tall.
Plant out into 150mm (6”) deep holes made with a dibber or trowel 150-200mm (6”-8”) apart, in rows 300 –400mm (12”-14”) apart.
Water each plant individually to settle soil around the roots.
Although shortening of roots and foliage is sometimes advised to reduce plant stress, it in fact decreases the plant's capacity to recover and should be avoided.
Shading can also be detrimental and is only necessary in the hottest weather.
If growing blanch leeks fit a cardboard collar around each leek when it is around 150-200mm (6"-8") tall and earth up around them with soil.
Try not to get soil between the leaves when doing so.
Alternatively, fit a 100-150mm (4"-6") diameter pipe approximately 600mm (24") long around each leek.
Feed every two weeks from now until the end of September feed with a low potash liquid fertilizer e.g Chempak No.2 or similar.
Alternatively, alternate feeds between nitrate of soda and superphosphate of lime at 30gms (1oz) per 5 litres (1 gall) of water.
Leeks for exhibition purposes are divided into three categories:
Pot: are not more than 150mm (6") from base to button.
Intermediate: are not less than 150mm (6") and not more than 350mm (14") from base to button.
Blanch: are more than 350mm (14") from base to button.
The button is where the first pair of leaves sometimes referred to as flags split e.g. V
The National Pot Leek Society give additional points for volume or cubic capacity measured on volume of blanched shaft.
Tables for the calculation of cubic capacity are obtainable from The Secretary of the National Pot Leek Society.