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Tips and advice for growing Leeks

You’ve got to admire leeks. They’re exceptionally hardy, generally trouble-free, and best of all they will provide beautiful long stems from autumn all the way through to spring at a time when other harvests are thin on the ground. Now’s the time to start thinking about sowing them…so let’s get started!

Leeks are very hardy vegetables, which in most regions will safely sit through frost and snow to be lifted as needed. You can prolong the harvest period by selecting a mix of varieties. Early season leeks are less hardy but will be ready for autumn, while mid and late-season leeks will give you smooth stems for winter and spring.

What Are Leeks?

Like onions and other members of the Allium family, leeks are bulbous vegetables with white flesh and leafy green tops. The bulb, however, is not round, but just slightly larger than the stem nearest the roots. The more rounded the bulb, the older the leek. Leeks are one of the more expensive onion varieties you'll find at the market. This does depend on location: In countries where they're commonly used, leeks are cheaper. Those who love the mild taste of leeks and the ease of preparation believe they're worth a little extra money.

Growing Leeks at a glance

Ease of Culture: Easy
Where: All zones
Best climate: Cool, and temperate
When to plant: Autumn and winter
Spacing: 10-20 cm
Harvest: Spring and summer (20-25 weeks)
pH: 6-7

Climate for Leeks

• Leeks prefer cool to warm conditions in the range of 12-25°C
• In cold areas, they are best sown in spring to early autumn for transplanting later
• In warm areas, plant in early autumn and harvest late winter/spring

Soil for leeks

• Leeks grow in a wide range of soils but like a well-drained soil moderately rich in humus
• It is a good crop to plant following a crop that has been heavily manured like corn or lettuce.
• Use a garden fork to loosen the soil well, and then mound the soil to help improve drainage.
• Add lime if your soil is acidic.

Position for Leeks

Leeks grow best in full sun but will tolerate part shade.

Sowing leek seeds

• Leeks are easy to grow from seed or seedlings.
• Seed is best sown into punnets for transplanting later.
• Fill punnets with a good quality seed raising mixture. Sprinkle seed on the surface and press the seed into the mixture to create close contact.
• Gently water seeds in and keep the mix moist until they germinate.
• Place punnets in a warm spot that gets a few hours of the morning sun
• After germination, keep the mix evenly moist and feed with a liquid fertiliser once a week to encourage healthy growth and establishment.
• Seedlings are ready for planting out around 8 weeks after germination.

Container Gardening Leeks

At this point, you'll either have some young leek seedlings or some roots to plant. Either way, the overall process of growing leeks in containers is fairly straightforward. Although leeks in containers is quite easy, there are a few steps that you'll want to follow to ensure a healthy and tender crop:

Leeks planted in a 12 litre container

When you're ready to plant outdoors, select a suitable container for leeks to grow in. A container whose depth is around 8-10 inches and volume measures 9 to 12  Litres do fine.

Fill the container 2/3 of the way full with premium potting soil. Leeks require a hefty amount of composted organics to maintain growth. The chosen potting soil should also be amended with sand or perlite to achieve proper drainage.

With the container two thirds full of potting soil, plant the seedlings or leek bottoms so that the root section is just below the soil line. Water in well. For small-medium sized leeks, utilize an all direction planting method ensuring 4-5 inches between plants. If larger leeks are desired, space 6-8 inches apart in all directions.

Place the newly planted container of leeks somewhere in the garden that receives a minimum of six hours of sunlight daily. Leeks will need this full sun (6+ hours) to survive.

Water the leeks so that the soil remains moist, but never waterlogged. I've found that watering thoroughly once a week is sufficient for proper leek growth.

As the season progresses and your leeks get larger, blanching of the stem should be performed. To do this, fill your container with soil or compost as the leeks grow taller. The additional soil will "blanch" the leek stem, turning it from fibrous green growth into tender white shoots

As long as you're using aged compost to blanch the leek stems with, fertilizing is generally not required. If you do feel inclined to do so, a nitrogen-heavy compost tea may be applied a few times during the season. Just remember, too much fertilizer can cause leeks to bolt.

Blanching Leeks

While all parts of the leek are edible, it’s the sweet tender white section that is preferred for cooking. 'Blanching' - the process of denying the lower section of the stems of sunlight as they grow - helps to increase the white section. This is achieved by planting seedlings deeply and covering the lower stems with a short section of PVC pipe or milk carton as they mature.

Planting Leek seedlings

• Dig planting trenches or rows 20cm deep and 20-30cm apart
• Separate and plant seedlings 10-20cm apart along the trench
• As the plants grow, gradually backfill the soil in the trench to cover and blanch the lower stems.

General Planting Guide for Leeks:

Method:              Sow direct or raise seedlings

Sowing depth:   5mm

When:                 Spring, summer, and autumn

Germination:     10-14 days at 18-23°C

Life Cycle:            Hardy Biennial (usually grown as an annual)

Row Spacing:      45cm

Plant Spacing:    12cm

Position:              Full sun, moist soil

Days to Maturity/Flowering:       110 days

*Notes: Keep well-watered. Hill stems with soil to blanch and create longer stems.

Watering and fertilising Leeks

• Water crops regularly to keep the soil moist.
• Sprinkle a little organic fertiliser along the rows once every six weeks to keep plants developing strongly.

Harvesting Leeks

• Leeks can be harvested at any time you feel they are big enough to cook with
• The ideal size for harvesting is when their diameter is around 2.5 cm
• Aim for a blanched section at least 10-15cm long.
• Large mature leeks may require a garden fork to help lift them out of the ground.
• Leeks can be left in the ground for extended periods without loss of quality – up to 12 months in cool to temperate climates (less in tropical and subtropical zones).

Pest and diseases

Leeks are largely pest and disease-free. Thrips may attack the foliage, but they cause little damage to the crop. Snails and slugs will sometimes lodge themselves between the leaves – inspect the plants periodically and pick these out.

In the kitchen

The delicate mild flavour of the leek can be enjoyed in soups, sauces, pies, tarts, and casseroles and sautéed and served as a side dish. Leeks need to be washed and cleaned thoroughly before cooking to remove the soil that collects at the base of the leaves.

How to Cook with Leeks

Leeks can be boiled, braised, fried, or roasted. They can be treated like onions, either sautéed in butter or olive oil or caramelized. However, you cook them, it's important to avoid overcooking leeks because they will get mushy, even a little slimy. The goal is to cook leeks until tender, though it should still require a little force to pierce them with a fork. When adding them to a recipe, you'll typically want to add the leeks near the end of the cooking time. Raw leeks are also a popular salad component.

Preparing leeks is relatively easy. Begin by cutting off the roots and the darkest green tops (these can be reserved for making stock). You will be left with a white stalk and light green leaves that are just beginning to separate; these are the edible parts. Cut each leek into quarters lengthwise but avoid cutting all the way through the white end. Rinse the leeks well, being sure to fan out the leaves that tend to trap a lot of dirt and debris. Pat the leeks dry, then chop, dice, or slice as needed.

Varieties that we sell

Elephant Leek

Allium Porrum

200 seeds/pkt Elephant Leeks

  • Large leeks
  • Good flavour

Large leeks can grow up to 10cm in diameter.  Good flavour.  Perfect for salads, stews, soups, stir-fries and steamed.

Leek Bulgarian Giant

Allium Porrum

200 seeds/pkt

  • Vegetable
  • Exceptionally long white stems
  • Exceptionally long thin white stalks with light green coloured leaves. Medium to early maturing variety. Mild and sweet flavour. Very popular in Europe. Its long stalks make it easy to handle in the kitchen.

Happy Gardening

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