At a glance
- The long white shaft is the goal with leeks. It comes from excluding light: you plant deep into a hole and earth up soil over the season.
- Set the young plants into the planting hole and just wash them in with water instead of filling the hole with soil. That keeps the shaft nicely pale.
- Protect the leek from the start with a fine-mesh net against leek moth and onion fly. Once they are in, little helps.
- Planting time is around CW 20 to 28. Winter leeks stay out into the frost and are harvested as needed.
The leek is the patient long-stay vegetable in the bed: it stands for months, tolerates frost and delivers just when little else is fresh in winter. Growing it is easy, but it all turns on a single question: how do I get the longest, most tender white shaft rather than a short green stub?
The answer is excluding light. Where no light reaches the leek, it stays white and mild. That is why you plant it deep and earth it up later. Let us look at it step by step.
Why the white shaft?
The white part of the leek is nothing but blanched leaf. As long as no light reaches it, the plant forms no green chlorophyll and the shaft stays pale, tender and mild. As soon as light falls on it, it greens up and turns firmer.
That is exactly why you work with depth and with earthed-up soil. The higher the soil stands against the shaft, the longer the white, prized part grows. That is the whole trick behind every good leek.
How to plant leeks properly
Take sturdy seedlings
Pre-grow leeks from February or buy seedlings. A transplant is ideal when it is pencil-thick. Plants that are too thin take forever.
Trim roots and leaves
Before planting, trim the roots to about two centimetres and the leaf tips by a third. It sounds harsh but spurs the plant to root strongly.
Set it deep into the hole
With a dibber, make a hole about 15 cm deep and let the seedling slide in. Most of the shaft now sits in the dark.
Only wash in, do not backfill
Do not fill the hole with soil; simply flood it with water. The soil settles loosely around the roots on its own, and the shaft has room to thicken.
Earth up over the season
Through the summer, keep drawing soil up against the shafts. Every centimetre of soil brings a centimetre more white. Take care that no soil trickles between the leaves.
- Typ
- Biennial vegetable, grown as an annual
- Familie
- Alliums
- Standort
- Sunny, deep, nutrient-rich soil
- Aussaat
- Pre-grow from February · CW 6 to 10
- Ins Freiland
- Plant out · CW 20 to 28
- Ernte
- Summer leek from CW 30 · winter leek CW 44 into spring
- Wasserbedarf
- Even, a heavy feeder
Summer leek is slim and quick, the winter leek by contrast is the tough one: it has dark blue-green foliage, stands in the bed all winter and is lifted as needed. A few winter leek plants are worth their weight in gold when almost nothing else is fresh.
The most important protection: the net
As easy-going as the leek is, two pests give it real trouble. The same simple measure works against both.
Leek moth and onion fly
The larvae of the leek moth and onion fly bore into the shaft and make it inedible. Once they are inside, you hardly get them out again. The reliable protection is a fine-mesh crop net that you lay tightly over the bed right after planting and keep closed. A crop rotation and distance from the last leek bed help on top.
Plant deep, earth up patiently, cover early with the net. A good leek needs no more.
The core rule for a fine leek
Frequently asked questions
Why is the white part so short on mine?
Because too little of the shaft stood in the dark. Plant deeper into the hole and earth up more consistently in summer. Every centimetre of soil against the shaft becomes a centimetre of white leek.
Can I really leave leeks outside in winter?
Winter leeks, yes. They are frost-hardy and lifted as needed all winter. In severe prolonged frost, a cover of leaves or fleece helps so you can get the ground open to harvest.
Why do the leaves crumble and turn yellow?
Often the leek moth or onion fly is behind it, their larvae feeding in the shaft. So protect with the net from the start. Persistent drought also yellows the leaf tips.
Do I have to water and feed leeks?
Yes, it is a heavy feeder. Work in ripe compost and water evenly in dry spells. Too much fresh nitrogen, though, makes it more susceptible, so feed organically and in moderation.
Does the leek go well next to other crops?
Very well next to carrots: the leek scent confuses the carrot fly, the carrot scent the onion fly. This old companion planting is one of the few with proven effect.
Sources
- Julius Kühn Institute: growing leeks in the home and allotment garden
- Bavarian State Institute for Viticulture and Horticulture (LWG): leek moth and onion fly
- Related in the magazine: Sowing carrots without carrot fly and The garden in July
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