Wednesday, 19 May 2010

Growing Leeks

  • Leeks are biennials, but grown as annuals, unless being grown for seed or for their bulbs, when they taste like onions or shallots.
  • They reach 45cm (18in) in height and upto 15cm (6in) across.
  • The edible part is the thick white shank that's below the blue/green leaves, known as flags by those gardeners who show them.
  • There are 3 types of Leek Varieties:
    1. Early – Harvest September, October and November.
    2. Mid Season – Harvest December, January and February.
    3. Late Season – Harvest February, March and April.
  • Leeks are easy to grow but they do require sowing in pots and then transplanting into the ground.
  • Leeks tend to be in the ground for at least 5 months but they are worth the wait to harvest in the winter through to the spring.
  • They are hardy and as such can survive winter weather and are generally not troubled too much by pests and diseases.
  • Leeks are a cool season crop, and grow best below 24 C (75 F) but they will tolerate higher temperatures if kept well watered. 

  • Leeks can tolerate a wide range of soil types, but they grow best on a moist, light soil that has been heavily manured from a previous crop.  
  • Be aware that freshly manured soil is not suitable, because leeks grown in very rich soil will be coarse and tough and with far too much leaf growth. 
  • If the soil is in need of organic matter, it is best to dig in well rotted garden compost.
  • In crop rotation, leeks follow lettuce, cabbage or peas, but it is not a good idea to plant them the same year immediately after lifting early potatoes. This is because the soil will be too loose and disturbed and leeks do best on a firmer soil. 
  • Choosing the site for sowing leeks may be influenced by the fact that they are generally left in the ground to be dug as required during the winter months, and they can remain in the ground for a year or more.  Don't grow leeks in the same place year after year as there will be an increased risk of pests and diseases.

  • Leeks need a long growing season, start them early as possible in the year, sowing in succession.
  • Sow seeds from March and April in seed-trays (flats), modules or pots in the poly-tunnel, greenhouse or mini greenhouse. 
  • A general purpose compost will provide a good seed base, but avoid composts with a large percentage of wood-bark, green-waste compost, wood waste, wood fibre or coir (made from coconut husks), as all of these reduce the water-retaining capability we get from peat, and that ability is important with leek seedlings, which should never be allowed to become dry. Avoid peat-free composts altogether, as they are a waste of both time and money.
  • Sow the leek seed thinly (about 2.5cm / 1in apart), as germination is usually very good and cover the seeds with fine sifted soil or compost.  
  • If the seeds are properly stored they will be viable for about four years, so you can keep seeds for future use. 
  • Germination should take about 14-21 days and then grow-on until ready to plant outside, from mid-May onwards in Central England.

  • By late spring to early summer when the largest seedlings are about 20 cm (8 in) high, they will be ready for transplanting to their permanent position. 
  • If you are able to plant during showery weather the young plants will settle more quickly, otherwise water the bed the day before if the soil is dry.  
  • The roots in the seed-tray will be entwined, so separate them gently, but do not worry about slight root damage, as we will be doing much more apparent damage ourselves later!
  • To plant leeks in holes, use a thick dibber or trowel and make the holes 15 cm (6 in) deep and 15-23 cm (6-9 in) apart, depending on what size of leek you want.  
  • Make sure the holes are vertical and move the dibber about from side to side so that they are slightly larger at the top.  
  • The holes should be about 5 cm (2 in) in diameter. 
  • Cut back the roots until they are 2.5 cm (1 in) long and trim the tips of the leaves back slightly, removing up to one-third from the largest seedlings.. 
  • Lower the young leeks gently into the holes and fill the holes with water.  
  • The water will wash enough soil over the base of the plant to allow it to become established. 
  • As you hoe the ground from time to time the holes will gradually fill up with soil. 
  • Bare soil is an open invitation to weeds, so carefully remove any stray weed seedlings, avoiding the grass-like young leek plants - it's essential to clearly mark the row so you don't remove plants by mistake.
  • Keep plants well-watered until they are well established, especially during dry spells - a mulch will help to retain moisture over summer.
  • Soon after planting apply a liquid manure. 
  • Hoe between the rows regularly to keep down the weeds and also this will aerate the soil. 
  • Frequent hoeing will also create a dust which helps conserve moisture. 
  • Leaves which grow too long can be trimmed back slightly so that they do not rest on the ground. 
  • Cut the long dark leaves back by about 5 cm (2 in) in early summer and again in mid summer, and a third time if it is necessary, in early autumn.

  • Depending on which variety and when sown, your leeks will be ready for picking from late summer, although the most useful types are those that can be picked over winter, when there's little else in the vegetable garden.
  • The hardier varieties are left in the ground until they are needed.
  • Never pull the leeks out of the ground by force or they will more than likely break in two, leaving you with just a handful of leaves. Instead, lever them out with a spade or a fork.  
  • Dig up the largest ones first, if you leave the smallest ones in the ground until the spring, they will put on some more weight before they flower.
  • If the ground is likely to be frozen for a long period of time, it is a good idea to lift any leeks which are ready and store them in some sand in a cool place, where they will keep for about a month.  
  • If by the end of the season you have a few leeks still left in the ground, but need to clear the plot, you can dig up the leeks and heel them in a shady place until they are needed. Lay them on their side in a shallow trench with the top part of the leaf stalk sticking out above the ground, covering the rest of the stalk with soil.  This also helps to stop them bolting.

  • You can, if you leave the leeks in the ground, nip out the flower stems and you will get a bonus crop, leek bulbs. These small white bulbs will form at the base of the plant, and if you harvest them in early summer you can use them as onions or shallots.
  • Always select leeks with a clean, white, slender bulb, at least two to three inches of white, and firm, tightly-rolled dark green tops.
  • The base should be at least ½ to 1 inch in diameter, although most are much larger, usually 1½ to 2 ½ inches. 
  • The younger the leek, the more delicate the flavour and texture. 
  • Look for the slim, cylindrical ones rather than those that are large and bulbous. If the bottoms are beginning to round into bulb shapes, the leeks are a bit too mature.
  • Check the centre of the leek for a seed stalk (the hard stalk can sometimes can be felt with a gentle squeeze) and avoid any you find. Those with a seed stalk beginning will have a tough, woody centre. If the leek is limp, leave it.

  • Leeks exude an aroma that can be absorbed by other things in your refrigerator, so to store them, lightly wrap them in plastic wrap to contain the odour and moisture. 
  • Do not trim or wash before storing, and place them in the vegetable drawer.
  • Depending on how fresh they are when you buy them, leeks can be stored anywhere from five days to two weeks. Cooked leeks should be covered, refrigerated, and used within a day or two.
  • Unfortunately, leeks are not a good candidate for freezing or canning, unless you plan to use them in soups or other recipes rather than as a main dish. Freezing tends to make them mushy and bitter.
  • If you decide to freeze leeks, cut into slices or whole lengths. Seal in airtight bags and use within three months. To preserve flavour, do not thaw before cooking further. Use frozen cooked leftovers for soup within three months. 
Leek Moth
  • This small brown Leek Moth lays its eggs on the base of the leek plants during mid and late spring. 
  • The emerging pale green caterpillars tunnel through the leaves, which are disfigured with white streaks. 
  • As more and more tunnels are made, the leeks loose their strength and my collapse and die.

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