When and How to Plant Out Leeks: Trim, Drop Into Deep Holes or a Trench, Water In

Prepare the bed before planting

Leeks are planted out from late spring into early summer in cool climates, once the seedlings reach pencil thickness and the soil is workable, and as the heat breaks in hot-summer climates. Choose a day when the soil is moist but not sticky. Because leeks stay in the ground for months and feed heavily, the work done on the bed beforehand decides much of the result.

1. Correct acid soil The onion family dislikes acid soil. If a soil test shows it is acid, apply garden lime a few weeks before planting and dig it in well.
2. Add plenty of compost About a week before planting, dig in well-rotted compost or manure and a balanced fertilizer. Rich soil pays off in late summer and autumn growth.
3. Check drainage Avoid spots where water sits after rain, since roots and stem bases rot in waterlogged soil. On heavy ground, improve drainage or use a raised bed.

Avoid beds that grew onions, garlic, shallots or leeks recently, because diseases of the onion family can persist in the soil. Keeping a simple record of where crops went makes rotation easier next year.

Lift and trim the seedlings

Seedlings are usually planted bare-root. The traditional practice is to shorten the roots and the leaf tips before planting. Trimmed leaves lose less water while the roots re-establish, and trimmed roots are easier to set in a hole or trench. Many gardeners skip the trimming and still get good results, so treat it as helpful rather than essential.

Sort the seedlings by thickness as you go. Planting similar-sized plants together keeps a row even, because small seedlings next to large ones get shaded and fall behind.

1. Water the day before Water the seedbed or tray well the day before, then ease the seedlings out from below with a trowel or fork rather than pulling them from dry soil.
2. Shorten the roots Trim long roots back with scissors to an inch or so (about 2.5 cm). This makes planting easier and new roots soon grow from the cut ends.
3. Trim the leaf tips Cut back the tops so the leaves are of similar length. Shorter leaves flop less and wilt less right after planting.
4. Keep roots covered Lay the trimmed seedlings under a damp cloth until planted so the roots do not dry in sun or wind.

Planting in dibbed holes

The classic way to plant leeks is the dibbed hole. The walls of a deep hole keep the lower stem in darkness from the start, so it grows long and white. It works best in soil that is loose but holds its shape.

The key step is filling the hole with water instead of soil. The water washes a little soil down around the roots, which is enough to anchor the seedling. The hole is then left open and fills in gradually with rain, watering and hoeing as the stem thickens.

1. Make deep holes Push a dibber or a thick stake about 6 inches (15 cm) into the soil, twisting as you pull it out so the sides do not collapse. Space holes about 6 inches (15 cm) apart in rows about 12 inches (30 cm) apart.
2. Drop in one seedling Set one seedling into each hole so that only the top few inches of leaf show above the surface.
3. Fill with water, not soil Pour water gently into each hole until it is full. Do not backfill; the water settles the roots and the hole closes naturally over the following weeks.

Planting in a trench

A trench does the same job as dibbed holes and suits heavy soil, where holes can smear and hold water. The soil taken out is piled alongside and drawn back in later as the leeks grow, which blanches the stems without extra effort.

1. Dig the trench Dig a trench about 6 to 8 inches (15 to 20 cm) deep and pile the soil neatly along one side for earthing up later.
2. Set seedlings against the side Stand the seedlings against one wall of the trench about 4 to 6 inches (10 to 15 cm) apart. Crowding them gives thinner leeks.
3. Cover just the roots Draw in only enough soil to cover the roots and firm it lightly. Filling the trench at once slows establishment.

Decide which side the spoil goes on before you dig, and keep it there. It makes earthing up through the season quick and tidy.

After planting

Newly planted leeks have few roots and are vulnerable to drying out and heat. Careful watering and weeding until fresh growth appears sets them up for the rest of the season. Some leaf tips may brown back after the move, which is normal as long as new leaves emerge from the center.

1. Water straight away Water at the base right after planting to settle soil around the roots, and keep watering in the mornings during dry spells.
2. Mulch the row A light mulch of straw or grass clippings in the trench or between rows holds moisture, keeps the soil cooler in summer and suppresses weeds.
3. Look for new leaves New leaves growing from the center mean the plants have rooted. From then on, start feeding and earthing up as described in the hilling guide.

Planting leeks in containers

Leeks grow well in containers as long as there is depth for the stem. Choose a deep pot, tub or grow bag, fill it only about halfway at planting, and add more mix as the plants grow. Topping up gradually blanches the stems the same way earthing up does in the ground.

1. Choose a deep container Use a large, deep pot or grow bag. A shallow container leaves no room to add mix and the white stem stays short.
2. Start half full Plant the seedlings into a container filled about halfway, leaving space above to top up with mix later.
3. Water thoroughly Containers dry faster than the ground, especially in summer. Water until it runs from the drainage holes whenever the surface dries.