Why Is My Leek Shank Short and Mostly Green?

The white, blanched portion of a leek shank — the pale section below where the green leaves emerge — is produced by excluding light from that part of the stem. Light turns the shank green; darkness keeps it white and tender. A leek with a very short white section and a long green shank is simply not getting enough soil coverage over the lower stem. This is a growing technique problem, not a disease, and it is entirely preventable with the correct planting and earthing-up method.

The traditional planting method — dibbing holes

The classic method for producing a long white shank is to use a dibber to make deep holes (15–20 cm) in the planting bed, drop a leek transplant into each hole so that only the top few centimetres of leaves are visible, and water in without backfilling the hole. The soil crumbles in around the shank over the following days and weeks, and the length of the shank buried in darkness becomes white and blanched. The deeper the planting hole, the longer the blanched shank at harvest. Many home growers transplant leeks at only 10 cm depth, producing a short, mostly green shank.

Earthing up to extend blanching

As leeks grow, the shank continues to lengthen above the original planting depth. Earthing up — drawing soil around the shank with a hoe or by hand, several times during the growing season — extends the blanched white portion progressively upward. Each time the green shank has grown 5–8 cm above the soil surface, draw more soil up around it. This ongoing process can double or treble the length of the white shank compared to a plant that was simply planted and left. Avoid pushing soil into the centre of the leaves; keep it around the outside of the shank.

Growing in trenches

A more involved method is to grow leeks in trenches — dig a trench 20–25 cm deep, transplant the leeks into the bottom, and gradually backfill and earth up throughout the season. This is more labour-intensive but produces the longest shanks and is used by show growers aiming for maximum blanched length. For everyday home growing, deep hole-planting combined with regular earthing up produces very satisfactory results without the trench excavation.