I grow leek in a foam box, just like my sister who lives in Ireland.

My sister Hanna gave me this tip about leek a few years ago. She has a large kitchen garden in Ireland, where the climate is a bit different of course. But I think this tip is relevant for us up here in the north too.

It's really easy to overwinter leek in Ireland. It can be a bit more difficult here in Sweden and zone 3, where you need the really hardy varieties. I don't have any favorites and like to experiment with different ones. I usually pick one that's very hardy plus a fast-growing early variety too.

The little leek plants were broadcast sown in a trough. They are very easy to divide when it's time to plant them.

Growing in a foam box

It takes a while before you can harvest the leek, so I sow mine already in January/February. Then you have to wait what feels like an eternity before they have grown large enough. I put the leek in a temporary spot the first time, so I can use the bed for something else in the meanwhile.

In this case, I plant my leek in a foam box filled with fertilized soil. You can, of course, use a trough too, as long as there is enough room for the soil. I will leave the leek here until June/July when it's hopefully as thick as a finger. That's when I lift them out and plant them in their final spot. It works really well!

I pruned my leek twice during late winter. This will make the plants easier to deal with later when the stalks are shorter.

Hardy varieties

I'm going to plant this batch in one of my polytunnels and make it part of my winter projects. The variety is called Carentan 3. You need a variety that you can sow in late fall and preferably also store for a long time. That's why I picked this particular variety. The variety Hannibal is also very hardy, it grows outside in my garden. They say its leaves are supposed to be a bit dryer so it won't freeze as easily.

More about alliums: Growing alliums from seed

The leek is coming along nicely!

Use fertilizer

While the leek is growing in the foam box, I will fill the box up with new soil as the plants grow. Make sure to fertilize them now and then too. I might also add a layer of grass clippings, water with nettle water, diluted urine or leachate from my bokashi compost. Try growing leek in a foam box at home too!
/Sara Bäckmo