Dedicated leek growers (not all of Welsh descent, I am sure) know that if they want a good sized harvest, plants need to be a finger thickness by Christmas. But it is not too late to sow seed now – the plants will just be a bit smaller. Leeks have a long growing season of up to 6 months and because they are a winter plant, they can then hold in the cold ground until you are ready to pick them.
Leeks are not fussy or particular. They grow easily in most soils. Because they belong in the leafy vegetable group, they thrive on nitrogen based fertilisers. This means they are going to be quite happy growing where you have recently dug in a green crop or if you have an area where you have previously added animal manures.
If you are going to sow seed, get it in as soon as possible. As the seeds germinate, you can use the thinnings as salad veg (they are a little like chives with an oniony tang). Final spacing needs to be about 10cm to achieve full sized leeks. If you are using seedling plants, you have a few more weeks up your sleeve and you generally plant them at final spacing. They are likely to need watering for the first few weeks while they get their roots out.
With vegetable gardening, you work one to two seasons ahead. Planting for winter now means you can avoid the hefty prices of bought fresh veg and have a change from interminable frozen peas. And leeks are an easy option. You just have to plant them in good soil and keep them relatively weed free (to stop competition) and in winter they should be waiting for you.