When To Sow: February-May Harvest: October-March
Germination: 6-16 days Full Sun to Partial Shade
Starting Indoors: Start leeks 8-10 weeks before your last frost date. Place 2-3 seeds per module in a sterile seedling mix. (It doesn’t hurt to add some blood, fish or bone meal in.) Cover with a sheet of plastic or glass and sit in a plate of water so that it waters from the bottom up. Place in a warm location. If you wish for stockier plants, keep the tops trimmed to no more than 3 inches.
Harden off gradually and transplant out into the garden once all threat of frost has passed. To plant out, drill a hole 8-10” deep, 4” wide, and with rows12-18” apart. Drop the leeks in one per hole and water well. (Do not fill the hole in with soil—just water. The leeks will grow into the space.) It’s easier to make all the holes and then go along the row dropping the leeks into them. Don’t worry if the leeks fall over after watering. They will sort themselves out soon and sit up right. Plant close enough together so that the leeks can touch each other as they grow.
If you have problems with pigeons pulling the young leeks up, place netting over the plants.
Direct Seed: After your last frost, direct sow seeds in rows 12-18” apart. Thin plants to 4-5”.
Maintenance
Keep your leeks well watered (twice a week during dry spells). Lack of water can cause leeks to have a stronger taste, a woodier texture, and will often grow unevenly.
For particularly tender leeks, blanch the stalk by hilling or mounding soil around it as it grows. (Hiding the white portion of the leek from light helps ensure its tenderness.)
Harvesting
Leeks are ready to harvest once they’re ½” in diameter or larger—usually by November. Lift by carefully loosening up the soil with a garden fork. Once loose, grab the shank and then pull. Harvesting leeks is dirty business, so feel free to rinse off your leeks before storing.
Giant Winter leeks store well in the ground, and in our British climes you should be able to lift at need all winter long.
Companion Planting
Leeks like any plant that loves the allium family, including carrots, celery, lettuce, all of which will improve their growth. Avoid planting near beans, peas, or other legumes.