Growing leeks from seed is incredibly easy. This is a vegetable that any beginner gardener can grow. You do not need to grow 3lb leeks for shows, just grow them to eat.
I use a trough with fresh (commercial) potting compost in it. Using a trough means you do not need to worry about watering every day as you would with seed trays. The plants develop better roots, too.
Plant your leek seeds in April. Just scatter a packet of seeds over the surface of your compost, cover with a thin scattering of compost and press down on the surface to ensure good contact between the moist compost and the seeds.
Leave your leek seedlings in the container until they are about 6in high. You can plant them in the ground or grow your leeks in pots and containers. They will grow well either way.
It will be July or early august when you are transplanting your leek seedlings. They can go in the ground after new potatoes, or just save space for them after harvesting spring cabbage.
Leeks, onions and garlic belong to the same family, so avoid planting them where you have just harvested these crops. Plant them 6-12in apart. Weeding leeks is best done by hand so you do not damage the young plants.
The length of white, blanched stem depends on how much of the leek is buried in the soil. The easiest way to plant leeks is to just drop one seedling into a dibber hole about six inches deep. You can get longer white stems by earthing them up as they grow in autumn, but I can never be bothered. You can use the green leaves just as well as the blanched ones in soups and casseroles.
I have grown leeks in large pots and they grow to full size if you plant three leeks to a B&Q bucket (Remember to drill drainage holes in the bottom.
Leeks need a good feed of nitrogen, so give them a good handful of pelleted chicken manure per square yard.
Your leeks will be ready from October to March. Just dig them up as you need them, even in a heavy frost.