378 Handbook of herbs and spices
wait until the plants reach 5 cm in diameter to pick the crop. Similar to onions and
garlic, growers may undercut the plants to facilitate harvest. After the plants are
removed from the soil, the roots are cut off, along with all but 5 cm of the green leaf
blade, leaving mostly the white sheath of overlapped leaves. The plants can also be
left in the ground over the winter but should be harvested in the spring before growth
resumes.
Leek yield potential is dependent on plant population. Row spacings of 60 cm and
plant spacings of 10 cm will give a stand in excess of 160,000 plants per hectare. If
we consider a harvestable crop at 80% of original stand, approximately 3600 cartons
containing 12 bunches of leeks will be marketed. Similarly, a row spacing of 91 cm
and plant spacing of 15 cm will give a stand in excess of 70,000 plants with harvestable
crop yield of approximately 1600 cartons containing 12 bunches (Randy Baker, 1991).
22.4 Uses in food industry/processing...................................................
The leaves and long white blanched stems are cooked. The sharp flavour of leeks
often disappears upon boiling, leaving behind a very mild, pleasant-tasting product.
They can also be cut into thin slices and be added to salads, which gives a mild onion
flavour with a delightful sweetness (Anon., 2005c). The thick leaf bases and slightly
developed bulb are eaten as a cooked vegetable or raw with or without attached
leaves. The green leaves are edible and have a pungent odour and acrid taste. They
are used more for flavouring in salads and cooked dishes. A favourite dish for many
gardeners is leek soup (Stephens, 1994). They are used primarily for flavouring
soups and stews in place of onions. Because of their symbolism in Wales they have
come to be used extensively in that country’s cuisines (Anon., 2005b).
22.5 Functional properties......................................................................
22.5.1 Nutritional value
The leek does not offer a great deal of nutrient value besides bulk and a pleasant
taste. The overall vitamin and mineral content corresponds roughly to that of onion.
Nutrition facts for leeks are furnished in Table 22.2 (Anon., 2005b). Table 22.3
shows the nutrients for which leek is either an excellent, very good or good source.
Next to the nutrient name the following information is furnished: the amount of the
nutrient that is included in the noted serving of this food; the % daily value (DV) that
amount represents (this DV is calculated for a 25–50-year-old healthy woman); the
nutrient density rating; and the food’s World’s Healthiest Foods Rating. Underneath
the chart is a table that summarizes how the ratings are devised (Anon., 2005a).
22.5.2 Health benefits
Leeks, like garlic and onions, belong to a vegetable family called the Allium vegetables.
Since leek is related to garlic and onions, it contains many of the same beneficial
compounds found in these well-researched, health-promoting vegetables (Anon.,
2005a).