I’ve been growing leeks using the same method for the past three or four years now and it seems to be working quite nicely.
Rather than tray-sowing and then pricking out individual leeks into modules, I use deep plastic troughs – the sort of thing you can find in most large supermarkets at this time of year or online of course – about half filled with general purpose compost. On top of that I layer about 5cm of seed compost, and sow the leek seed thinly on top, before covering lightly with seed compost and watering with a fine-rose can.
A few weeks later, the leek seedlings should be about 15-20cm tall and looking rather grass-like. This is when I like to thin them out and give them a trim.
If there are two or more seedlings growing within about 1cm of each other, then one or more of them has to be plucked out. Be ruthless. Better to have one good seedling with enough room to grow to planting-out stage than two or three that eventually compete each other to the point of uselessness. Plus, the leek-trimmings can be used like chives, in pasta, fritatta or anything else you fancy.
Next, take a pair of sharp scissors and give your leeks a hair-cut. I gather up a small bunch and then chop the lot off at around 10-12cm in length. Trimming the main growing shoot(s) helps to prevent them becoming hopelessly leggy and tangled. It also encourages the growth of new leaves from the basal plate at the bottom of the leek, and that’s what you want: a thickening of each seedling to roughly ‘pencil thickness’, ready for planting out in June or early July.
If you’re thorough (and brave) enough then you might only have to thin your leek seedlings once before planting out, although a second trim may be needed in another three or four weeks.
How about you? Is this how you grow leeks, or do you use a different method? Let me know via the comments.