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Allium porum
Allium porum

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Zones A3, 1-45, H1, H2
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Leeks (Allium porum) are related to onions but don’t form distinct bulbs. To 2–3 ft. tall, with an edible, mild-flavored stem that resembles a long, fat, green onion. Give very rich soil. Performs best in cool-summer climates, but also does well in hotter areas if given some shade.

In cold-winter regions, set out transplants in early spring, or direct sow seeds in late summer for harvest the following year. In mild-winter areas, set out transplants in fall. Sow seeds indoors 1/2 in. deep, 1 in. apart, 8 weeks prior to planting date. Space seedlings 2–4 in. apart in a 5-in.-deep furrow. As plants grow, mound soil around stalks to blanch them (this makes the stem bottoms white and mild), keeping mounded soil just below leaf joints.

Harvest when stems are 1/2-2 in. thick, usually about 4 to 7 months after setting out plants. In cold-winter climates, harvest before ground freezes. (Where ground doesn’t freeze, you can leave leeks in place and harvest as needed. ) Lift out with spading fork. Any offsets may be detached and replanted. If leeks bloom, small bulbils may appear in flower clusters; plant these for later harvest. To prepare leeks for cooking, slice off the roots and all but 2–3 in. of the green leaves; rinse thoroughly, separating layers. Leeks are not bothered by many of the pests and diseases that attack onions.

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