Leeks grow best in pH from 6.0 to 8.0 with 6.5 to 7.0 being optimum. When plants get to be 3 to 4 inches tall push extra media around the stem area up to the growing leaves. This will turn the stems white and make them more tender. Leeks need a night temperature of 55 degrees or greater, and grow best in a daytime temperature of 80 degrees or greater. Therefore, they should be planted to receive lots of sun in a warm place in the growing area.
Leeks also grow in the winter, but much more slowly.
After planting the seed, allow the young seedlings to grow to a height of about eight inches. You should then dig up the seedlings, removing half of the tops. They are then set back out spacing the plants about six inches apart. Downy mildew , Neck rot , Pink rot , Rust and Smut .