Gadenin日本語Get the appBlanching: earthing up and collars
The white part of a leek is the stem grown in darkness. Planting deep gives a good start, but most gardeners lengthen the white shank further by excluding light as the plant grows. There are two common ways to do it: earthing up, which means drawing soil up around the stems in stages, and collaring, which means slipping a tube of cardboard or plastic over each stem.
Whichever you choose, raise the soil or collar gradually, a little at a time, as the plant grows. Never bury the point where the leaves fan out from the stem. Soil that falls into the leaf joints ends up as grit between the layers, which is the most common complaint about homegrown leeks.
- Wait until the stems thicken Start once the plants are well established and the stems are noticeably thicker than at planting, usually a month or so after transplanting.
- Draw up soil in stages Use a hoe to pull loose soil up around the stems by an inch or two (2.5 to 5 cm) at a time, repeating every few weeks through summer.
- Or fit collars Slip a tube of cardboard, paper or plastic pipe over each stem, resting on the soil, and raise or replace it as the plant grows.
- Keep the leaf joints clean Stop each time just below where the leaves branch. Do it when the soil is dry and crumbly, not wet, so it does not slump into the plant.
Blanching is about quality, not survival. Unblanched leeks are perfectly edible; you simply get a shorter white portion and more green to cook with.
Soil: rich, deep and well drained
Leeks spend months in the ground and keep growing for most of that time, so they reward generous soil preparation. Dig in plenty of well-rotted compost or manure before planting, ideally the previous autumn, and aim for a near-neutral soil, roughly pH 6.0 to 7.5. Acid soil benefits from lime well ahead of planting.
Good drainage matters as much as richness. Leeks stand through the wettest part of the year, and waterlogged soil over winter encourages rot at the base of the stem. On heavy ground, a raised bed or extra organic matter makes a real difference.
| Factor | What leeks want | Why |
|---|---|---|
| Organic matter | Plenty, dug in before planting | Long season, heavy demand for nutrients |
| Soil pH | Around 6.0 to 7.5 | Very acid soil gives weak growth |
| Drainage | Free draining, especially over winter | Wet soil causes rots at the base |
| Sun | Full sun | Shade gives thin stems |
Feeding through the season
Leeks are leafy plants and nitrogen is what they use most. A balanced fertilizer raked in before planting, followed by a side dressing or liquid feed every few weeks through early and midsummer, keeps them growing steadily. Stop feeding heavily by late summer, especially for late cultivars that will stand through winter. Soft, lush growth late in the season is more prone to leek rust and less able to take hard frost.
- Base dressing before planting Work compost and a general balanced fertilizer into the bed at the rate on the package, a week or two before transplanting.
- Side-dress once growing When the transplants show new growth, scatter a nitrogen-rich fertilizer along the rows and water it in, or use a liquid feed every two to three weeks.
- Ease off by late summer Tail off feeding as summer ends. Firm, steadily grown leeks stand the cold better than soft ones pushed with extra nitrogen.
Steady moisture, no checks
Leeks have relatively shallow, fibrous roots and dislike drying out. A dry spell in summer slows growth and can make the stems tough. Aim for about 1 inch (2.5 cm) of water a week from rain or watering combined, soaking the soil rather than sprinkling it. A mulch of compost or straw between the rows once the soil is warm holds moisture and keeps weeds down.
Leeks have narrow upright leaves and cast very little shade, so weeds grow freely around them. Hoe shallowly and often, especially in the first months; weeds compete hard for both water and nitrogen.