Leeks can be readily sown from seed in January, in a greenhouse or under grow lights, and transplanted outside in early April (in my zone 6), but these should be grown all summer and then overwintered for good size the following spring. I prefer to grow from started plants, such as these, which I get from Johnny’s at three bunches (of about 50-60 each) for $29.
Of each bunch, I select those with the largest bulbs and roots (seen here), and let the rest do for themselves in a pile of compost. Using a dibble, I plant each “leeklet” in a 6″ deep hole, with only 1 or 2 inches of each plant sticking above the soil. I let rain or irrigation water fill in the hole. I keep them weeded and mulched, then ignore them lest I get too anxious. Our time will come….