How I Sow and Grow Leeks
I grow our leeks from seed and usually just make the one sowing a year. This is because I don't feel the need to stagger the sowings in order to provide ongoing harvests throughout the year. Leeks store perfectly well in the freezer and taste great, so there's no great issues with sowing and planting them all at once and then harvesting them all at one.
The most effective way of starting to grow leeks I have found is by broad sowing them into a large pot. I start off with a 7 or 8 inch pot, filled with my normal seed starting compost. It gets firmed down a little and then watered.
From there, the seeds are sown onto the compost surface. Then, an additional covering of around 1cm of seed mix is added.
While some people prefer to start them off with a little heat, either by germinating them indoors or on heat mats, they should also germinate reasonably well in a polytunnel from early to mid February. Once sown, these two tubs (2 different varieties) were left in the grow tent until the next time I went up to the allotment and I could take them to the polytunnel.
As with many seedlings, they are usually watered best from the bottom, so once in the polytunnel, they are sat in a tray with water and left to germinate.
Growing these leeks is a bit of a waiting game. I have found that providing germination is pretty good, it can take months before they are ready to undergo the next stage. They need to be left until they have a reasonable thickness to them. In many books and guides, it will tell you to wait until they are the thickness of a pencil. While there is no reason to dispute that, or go against that advice, I have found that transferring them out when they are a bit smaller doesn't seem to make any difference.
After several months in the polytunnel, they will eventually be big enough to be transplanted out into their final locations.
Ahead of transplanting out, I don't prepare the ground in any particular way. I just make sure any weeds are removed, and generally, the bed would have had a couple of wheelbarrows of digestate or manure during the Winter before. This should be everything the leeks need to continue to grow, although added chicken manure pellets are also useful to aid the green growth through the Summer period if you wanted to.
For transplanting, I remove the whole clump of leeks from their pot, and then put them into a half bucket of water to soak. This allows the compost to release easier from the root system of the leeks and makes separating the individual plants much easier. Then, using a big dibber, holes are put in the bed, ready for the plants to be dropped in. You can use the seed packet as a guide for spacing, but I always make sure that there is at least enough room to run a hoe along the rows, but also between the plants.
I choose the thickest and strongest of the leek plants to be transplanted out, one leek per hole. But, never backfill the hole with soil or compost. For the coming days (unless it rains) I fill each hole with water. The soil from around the hole will naturally fall into the hole, and encase itself around the leek, but will be quite loose. This allows the leek to continue to develop and start adding thickness.
The leftover leeks are either given away or added to the compost heap. When the leeks get to the sort of size as the ones above, sometimes I will 'earth up' around each leek. That just means that I will pull the surrounding soil in and stack it up around the stem of each leek. This is quite time consuming, but it also encourages the leek to blanch more of it's stem, giving you more white colour to the leek and encourages the green growth to continue pushing upwards.
The, it comes to harvesting. Despite using mesh of different types over the years, I've come to the conclusion that in many cases, there is nothing I can do about leaf miner population, or the dreaded rust fungus. So, choosing, or knowing when to harvest the leeks at the end of the growing period is a bit of a dark art. You want to leave the leeks to continue to grow as much as you possibly can. If possibly, well into Autumn. But, once rust fungus sets in and starts to take hold, it can ruin the crop, or at least make it less appealing to being eaten. Rust resistant varieties are available, but can be expensive I have found.
Less easy to spot without digging up a couple of leeks is the leaf miner. The first signs may look like little specs of dust, but could also look like little nicks or cuts in the leaves or stem of the leek. It is not until you start peeling back the layers of the leek that you can truly see if there is any sign of internal damage. Because of these issues, I often end up harvesting leeks a little earlier than I would otherwise like to, preventing any serious spread or infestation of either fungus or pest.
