A favorite soup and stew vegetable thanks to its mild onion-like flavor, leeks can be a challenge to grow if you don’t know the right technique. Leeks have a long harvest time of about 130 days, but you can shorten this considerably and harvest your leeks earlier in the season. To get a jump start on the spring growing season, plant your leek seeds indoors in a planter pot. Start the leek seeds about 8 to 10 weeks before the last expected frost and transplant the seedlings outdoors after all chance of frost has passed.
Sow the Leek Seeds
Fill the 6-inch planter pot with an all-purpose potting mix. Dampen the potting mix evenly with water and pack it down with your hands.
Allow the soil to warm to room temperature by placing it in a sunny window. Ensure that the potting mix is about 75 degrees Fahrenheit.
Insert the leek seeds about ¼ inch deep into the potting mix, spacing them about 1 inch apart. Water the potting mix to moisten it thoroughly.
Place the pot in a sunny window after the seeds begin to germinate and sprout. This usually takes about 10 days to two weeks.
Feed the seedlings a water-soluble commercial plant fertilizer at half the regular dosage. Feed them once every week to boost growth.
Mist the potting mix with a water spray bottle when the surface feels dry to the touch. Keep air temperatures between 65 and 75 degrees Fahrenheit during the daytime and around 55 degrees at night.
Thin out the weakest seedlings after they grow to about 2 inches tall. Transplant the strongest seedlings into individual plant pots filled with the same all-purpose potting mix.
Prepare the Leek Seedlings for Transplanting
Harden off the seedlings beginning about one week before the last expected frost. Place the plant pots outdoors in a sheltered spot during the day for a few hours, increasing the amount of time the plants stay outdoors until they’re outside all day at the end of the week. Bring the pots inside at night.
Dig a trench 5 inches deep. Work some organic compost or aged manure into the displaced soil.
Remove the leek seedlings from the plant pots carefully. Place the seedlings into the trench, spacing them about 6 inches apart.
Replace a small amount of soil into the trench, just enough to cover the leek seedlings’ roots. Gradually refill the trench with the amended soil throughout the summer so that you cover only the lower part of the stem with soil, encouraging the stem to blanch and grow long.