Grower’s Corner – Jerusalem Artichokes
The first thing to note is that leeks are a cool season crop, and although they will tolerate temperatures above 24 C (75 F) you will need to keep them well watered.
They are also biennials grown as annuals, reaching an average of a foot and half in height and anything up to six inches across. The blue/green leaves known as flags and the edible part below the flags may be blanched by earthing up or deep planting. Leeks prefer a sunny, sheltered site with well-drained soil. As they will sit in the soil for a long time, they are ideal crop for the allotment. If possible, prepare the soil for planting in the previous winter. Dig the site well, removing weeds and working in plenty of well-rotted manure to improve its ability to retain water. Leeks can be planted in heavy soil, but improve the drainage by mixing in some horticultural sand. This is a hungry crop – so broadcast a general fertiliser over the soil a week or so before sowing and rake it in.
Sowing seed
The easiest method is to sow seed directly into the soil between March and April. Alternatively, you may choose to invest in ready-grown seedlings and by a mixture of both and a careful choice of varieties you could have an ample supply of leeks to harvest from mid-summer until the following spring.
On an allotment, seeds are best sown in rows, a foot apart. Mark a straight line and use the corner of a rake to make a shallow groove in the soil, about half an inch deep. Sow seed thinly along the trench, cover with soil, water and label. When seedlings have three leaves each, thin seedlings to 3-4 inches apart in the rows.
Seedlings are ready to plant out when they are 5 inches high. Water the rows the day before planting, plant firmly with lower leaves just above ground level, space plants 18 inches apart. Keep well watered until the leeks are well established, then only water in dry conditions or if the weather becomes too hot (see above) but keep the beds weed free by regular hoeing. Mulch to retain moisture. Don’t allow them to flower or they will become bitter.
Problems
Leek rust shows up as bright orange or brown pustules on leaves and stems. Mild infections do not render the vegetable inedible but severe infections can lead to extensive leaf death and reduced yield. It is caused by overcrowding, high humidity, excessive soil nitrogen and insufficient soil potassium so to prevent it space plants generously apart, apply a potassium-rich fertiliser (such as a tomato fertiliser) and practice crop rotation. If it manifests, cut off affected leaves and dispose of them, but not on the compost heap.
Leeks may be harvested four to five months after sowing, but they can stand for many months, and can be lifted when required, because leeks don't store well when out of the ground. If you need the ground to plant something else, considering digging them up and heeling them in somewhere else on the plot until needed.
Leek photographs by indigo goat and author’s own, used under a creative commons attribution licence