Leeks are the winter hero of the organic garden — winter varieties survive down to -15°C, giving fresh vegetables from November to March. 🌿
Varieties
| Variety | Season | Frost hardiness |
|---|---|---|
| Summer leek | August–October | Weak |
| Autumn | October–December | Medium |
| Winter | December–March | STRONG (-15°C) |
Growing steps
- Start seedlings indoors in January-February
- Transplant in April-May, when the seedling is pencil-thick
- Dig a 15 cm deep hole, place the seedling in it, water it — don’t fill the hole, it fills in on its own
- Earth up 2-3 times: this whitens the stem (that’s the edible part!)
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Summary
Leek: seedlings indoors + earthing up for white stems + winter variety → fresh vegetables from the garden starting in January! 🌿
- Why shouldn’t you fill in the 15 cm deep planting hole when transplanting leek seedlings?
Leaving the deep hole empty provides exactly the dark, air-excluded environment the lower part of the stem needs to avoid producing chlorophyll — this is what gives leeks their characteristic white, tender stem. If we filled the hole immediately, the lower part of the stem would get sunlight from the start of growth and turn green and fibrous, losing the valuable, tender white section.
- Why does the stem need earthing up 2-3 times during the season instead of just once?
Leeks keep growing upward continuously throughout the season, so if we only banked up soil around the stem once, the newly grown upper part of the plant would soon get sunlight and start to turn green. Gradual, multi-stage earthing keeps pace with the plant’s growth, ensuring the longest possible section of stem stays white and tender right through to harvest.
- Why can winter leek varieties survive down to -15°C while summer varieties are ruined by even a light frost?
Winter varieties have been bred to develop a physiological adaptation that lets them accumulate natural “antifreeze” sugars in the cell sap, which lowers the sap’s freezing point and protects the cell walls from damage by ice crystals. Summer variety breeding instead focused on fast growth and tolerating summer heat, so this frost-protection mechanism was never developed in them.
- Why is pencil-thickness specifically the right time to transplant leek seedlings, rather than earlier or later?
A seedling that’s too thin and young doesn’t yet have a root system developed enough to withstand the stress of transplanting and the conditions of a deep planting hole, so it would likely die or fall behind in growth. A pencil-thick seedling already has a strong enough stem and root system to establish successfully in the deep hole, while still being young enough to adapt flexibly to its new environment.