Growing leeks: What to plant, when to to it, and how to make them thrive

Of all the vegetables, I think it is leeks (Allium porrum) that I eat in most increasing quantities every year. I think this might be after discovering how good they are when sliced lengthways almost to the base, wrapped in foil with a little olive oil and garlic and baked until tender. It is, therefore, with renewed enthusiasm that I dedicate myself to growing them this year.

Leeks are relatively easy to grow well, although they are particular and the quality of your harvest owes much to the small details. Sow in modules undercover from February, planting out in June or July when 8in or so tall: carefully tease out of the module, trim the roots to 2in, make a hole 6in deep with a pencil and lower the leek gently into it. Allow 8in or so between plants and water well.

Contrary to every instinct developed over years of planting out other seedlings, don’t backfill the hole with soil, but leave the leeks loose. As they grow, they thicken to fill the hole and expand more besides. With some varieties — try ‘Chef’s White’ and the appropriately named ‘Winter Giant’ — you can even sow direct from early spring, taking the thinnings as baby leeks and leaving the rest to mature.

Leeks flourish in a moisture-retentive soil in full sun; keep them weed free, water every few days during dry spells and — if you can be bothered — earth up as they develop for a greater ratio of white to green leaves.

I tend to grow the same varieties each year — those I know are full of flavour and give me a naturally staggered harvest. My early varieties are ‘Chef’s White’ and ‘Monstruoso de Carentan’, with ‘Winter Giant’, ‘Bleu de Solaise’ and ‘Musselburgh’ ready later in the season.

The habit of growing baby leeks came from impatience and endures due to their succulent deliciousness: I sow them from April, 1in apart with 4in between rows in a bed with a fine tilth, in successional batches three weeks apart for a steady harvest. Although all varieties work perfectly well, ’King Richard’ is a good, very early variety that also makes for superb baby leeks. Depending on variety, leeks can be ready to harvest from September, although most are happy to stand through winter, with baby leeks ready in summer when pencil-thick and resembling spring onions.

Rust — appearing as orange/brown blotches — is tedious, although largely aesthetic, rather than substantial in its effects. I use a seaweed or comfrey feed every fortnight that helps minimise its likelihood, but crop rotation is the most effective preventative. In the relatively rare occasion of a more serious infection, dig up all affected plants and burn them. If leek moth is a problem, cover your developing plants in fleece.

‘King Richard’ is a good, very early variety with superb baby leeks'

Although grown almost exclusively as an annual, leeks are hardy biennials and, if you allow a few to grow on, the reward will be their beautiful flower-heads and an abundance of pollinators and other insects drawn to their flame. Pinch off a few of those mini-florets, and scatter through salads or in a mayonnaise.

I also grow Babington’s leek (Allium ampeloprasum var. babingtonii). It flourishes in the cold months, making it an elegant, structural part of the cold-weather garden, as well as a welcome late-winter/early-spring harvest. Sweeter than familiar leeks, Babington’s leeks carry a gentle garlic flavour and are really good either griddled whole until softened and charred, or, as above, wrapped in foil, with garlic and a little olive oil and baked until tender. To harvest, cut long stems to about 1½in from the base.

As with other leeks, any you leave unpicked will develop long, arcing stems topped with glorious seedheads, perhaps 6in or so across. As well as attracting insects, the florets and immature seeds are delicious strewn across everything from pizzas to salads. Start from a young potted plant or from bulbils, which can either be sown in one-litre pots for planting out later, allowing 20in or so between plants, or — a little riskily — sown direct.

If you are lucky enough to know someone who grows Babington’s leeks, bribe them to allow you to lift, divide and replant, making off with some of your own: this is also the way to expand your own colony when established. Babington’s leeks are pretty resilient and unfussy about their location: avoid extremes of drainage and pH and they should thrive with little attention.

Mark Diacono grows edibles, both usual and unusual, at Otter Farm in Devon. His book 'Abundance: Eating and living with the seasons' (Quadrille, £30) is out now.

Mark is lucky enough to spend most of his time eating, growing, writing and talking about food. He has written fourteen award-winning books, including A Year at Otter Farm and A Taste of the Unexpected (both won Food Book of the Year, and Garden Book of the Year). Known for growing everything from Szechuan pepper to pecans to Asian pears, Mark's refreshing approach to growing and eating has done much to inspire a new generation to grow some of what they eat. He was involved in the early days of River Cottage, appearing in the TV series, and writing four River Cottage books. Mark writes to a global audience on his best-selling Substack: Mark Diacono’s Abundance.