
Plant them 1/2 inch deep & thin to 1 inch apart when the seedlings are about 3-4| tall. Leeks prefer temperatures of 60-65 degrees when being transplanted. Harden them off by moving them outdoors as soon as your soil is workable. Add additional soil around the plant as it grows to produce the long white stalks, that you so typically may see in culinary dishes. How to Grow Organic Leeks from Seed »