Fear not: those wimpy seedlings will grow into these!
(Note: I think this post needs a subtitle of "How to torture your leeks" because that's what I'm going to tell you how to do!)
If you are growing leeks for the first time this year, congratulations! I've grown them off and on for years and just love their delicious, delicate flavor. We use them in leek and potato soup, in casseroles, omelets and as a fancy substitute for onions.
I planted my leek seeds indoors on March 5th. I already knew that the seedlings would look like the wimpiest plants around, but please be assured they will look much better in a few weeks.
When they first germinate, they look like a thin blade of grass (see below). It's hard to believe they will eventually be huge. But for now, they are not impressive at all. In order for them to be ready for transplanting out into the garden in a few weeks, you have to periodically give them little "haircuts."
As you can see, young leeks are pretty tiny.
Let the seedlings grow to 3 or so inches tall, then trim them with a scissors so they are only 2 inches tall. Then you let them grow for a couple of weeks, and trim them back to 2 inches again. I know that seems crazy, and even like they might stop growing, but what you're doing is forcing each plant to devote its energy on developing a strong root system. Keep this up until they're moved outdoors.
When you're ready to transplant them out in the garden -- after the danger of frost is past -- this requires a somewhat unorthodox planting method as well. You need to dig a trench that is about 8 inches deep. Carefully plant the leek seedlings at the bottom of the trench, only covering the roots and the lowest part of the stem. You don't want to bury them up to where the leaves come out of the main stem because having soil in that area can cause the plant to rot. Space the seedlings about 4 inches apart.
Gently water the seedlings at the bottom of the trench to avoid having the sides collapse onto them. As the plants grow, you will slowly but surely fill in the trench around the seedlings -- always being careful not to get soil where the leaves attach to the stem.
The reason you're doing this is to "blanch" the lower area of the stem -- this means keeping the sun off of the lower stem, thus causing it to stay white in color. That's the main area of the plant that you'll eventually be eating.
You can start harvesting the leeks in the fall and can even leave them in the ground for a while but be sure to dig them up before the soil freezes. (been there, didn't do that once, and the plants ended up turning to mush after freezing a time or two)
I should mention that for growing leeks in regions with shorter growing seasons and cold winters, I'd recommend you grow a short-season variety like 'King Richard' which matures in 75 days. In milder areas, gardeners often grow a longer-season variety, planting them in the fall and harvesting them the following summer.