Advice Plot #59

Thinning and Trimming Leek Seedlings

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.

May 2017 leeks for trimming
Long and leggy leeks need cutting down to size


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.

8 replies on “Thinning and Trimming Leek Seedlings”

I don’t trim or thin my leek seedlings. Admittedly they’re never pencil thick when planted out in the garden, but I also start them very late as well usually mid-March. It’s just easier for me to keep them alive when they’re in my direct care for a shorter period of time while in containers . We can have terribly hot springs once it hits, and it can take watering twice a day just to keep seedlings alive in their containers.

I know Michelle from Seed to Table starts leeks in a nursery bed out in the garden. And since her winters are very mild she starts them very early indeed and they are massive when they get planted to their permanent location, like the size of leeks I might harvest early. Although, she doesn’t grow leeks anymore due to a local rust problem.

Hi Phuong – those hot spring conditions do sounds challenging. We’ve had a couple of unseasonably hot spells this spring and our greenhouse has been absolutely roasting, so lots of watering required. The nursery bed method is one I saw on a TV programme once – I think they were growing for the veg gardens at Kew – but I’m usually not quite organised enough for that sort of thing so early in the year 🙂

I admit to lacking the courage to thin leeks. So I sow the seeds in a pot at home and then, once they are well established, take them to the allotment plot and top and tail them: Tip out the whole pot and extricate the leek plants, discarding any real weaklings. Then I take a bunch of about a dozen in hand I collectively remove any roots longer that an inch with a knife. I also remove the top third of the top growth before popping each individual into a dibbed hole and then (the fun bit) puddle them in. Last year the results were a bit disappointing, but then again everyone in the UK seemed to find last year a disappointing year for leeks.

Hi Mal – That’s pretty much how I do it as well, I just like to get them to as robust a size as I can before I plant them out – topping and tailing, as you say – hence the thinning. Our leeks went in very late last year for one reason or another, so it’s tricky to compare. But find the smaller ones I’ve been harvesting are packed full of flavour, so I’ve no complaints on that score.

Question: I live in FL. I would like to cut back my leek stems for dehydrating. They are about 8 – 12 inches high but not thick. Will they regenerate? Is this unadvisable?

Hi Connie – Assuming US ‘leeks’ are the same as UK ‘leeks’ (Allium porrum) then yes, they should re-grow, as long as you leave the base-plate – the base of the stem from which the roots emerge – un-damaged.

I’ve had leeks re-grow from sections that have been left behind when I’ve tried to pull them out and snapped them off near the base instead. It might take a full season for them to reach a decent size again, and there’s always a risk of the base-plate rotting away or drying out, but it’s worth a try.

I’ve never heard of de-hydrating leeks though. I suppose it’s much like drying onions for use as a cooking ingredient?

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