Common Name: Welsh Onion

General Information

Allium fistulosum is a usually evergreen, herbaceous, perennial plant producing 2 - 6 hollow, cylindrical leaves 25 - 40cm long and a flowering scape 30 - 50cm (occ to 100cm) tall from an underground bulb. The plant divides quite freely, forming a cluster of growth[].
The Japanese bunching onion, often called the welsh onion in Britain, is widely cultivated in eastern Asia from the cold temperate regions of Siberia to moderate elevations in the tropics of southeast Asia and commonly sold in shops and markets. A very common vegetable in Asia, where there are many different cultivars, it is usually grown more on a garden scale in Europe and America, mainly for its edible leaves which can be produced throughout the winter if the weather is not too severe[, ].

Known Hazards

Although no individual reports regarding this species have been seen, there have been cases of poisoning caused by the consumption, in large quantities and by some mammals, of certain members of this genus. Dogs seem to be particularly susceptible[].

Botanical References

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Range

E. Asia, possibly western China, though the original habitat is obscure

Habitat

Cultivated for over 1,000 years, it is not known in the wild.

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Bulb
Height	0.40 m
Pollinators	Bees, Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

Allium fistulosum is a very cold-tolerant plant that originated in the temperate zone and is widely grown there. Plants will often retain their leaves even when covered in snow[]. In the tropics, it can be grown successfully at elevations between 1,000 - 2000 metres. High temperatures encourage bulb formation, but flower formation and seed production are only possible where the bulbs are subjected to low temperatures. In the tropics, flower and seed formation will therefore only occur at higher elevations[]. The plant grows best in areas where annual daytime temperatures are within the range 12 - 25°c, but can tolerate 6 - 30°c[]. It prefers a mean annual rainfall in the range 850 - 1,600mm, but tolerates 700 - 2,500mm[].
An easily grown plant[], it prefers a sunny position in a light well-drained but moist soil[, ] but tolerates most soils[, ] including those that are damp and acid[]. Prefers a pH in the range 6.5 to 7.5[], but it tolerates a pH in the range 4.9 to 8.5.
Average yields of leaves may be 34-45 t/ha[].
The oriental forms of this species, known as bunching onions, tend to be hardier and more robust than the welsh onion[]. There are two basic forms, multi-stem types and single-stem types. The single-stem types divide less freely than the multi-stems[].
The plants are often eaten by slugs[].
The bulbs should be planted fairly deeply[]. Most members of this genus are intolerant of competition from other growing plants[].
The plant probably arose through cultivation from Allium altaicum[].

Edible Uses

Bulb - raw or cooked[]. A strong onion flavour, it can be used in salads, as a cooked vegetable or as a flavouring in cooked foods[, ]. The bulbs are rather small, usually 10 - 25mm in diameter though they can be up to 45mm[], and are sometimes used as spring onions[]. A nutritional analysis is available[].

Leaves - raw or cooked[]. They have a mild onion flavour[] and can be added to salads or cooked as a vegetable[]. The leaves are often available all through the winter if the weather is not too severe[]. They contain about 1.4% protein, 0.3% fat, 4.6% carbohydrate, 0.8% ash, some vitamin B1 and moderate levels of vitamin C[].

Flowers - raw. A pleasant onion flavour, but they are rather on the dry side[].

Medicinal

The therapeutic qualities attributed to the welsh onion are many, especially in Chinese medicine. It is used to improve the functioning of internal organs and the metabolism, and to prolong life. It is further reported to improve eyesight, to aid digestion and perspiration, and to enhance recovery from common colds, headaches, wounds and festering sores[].
The bulb contains an essential oil that is rich in sulphur compounds[]. It is antibacterial, antiseptic, diaphoretic, diuretic, galactagogue, stomachic, vermifuge and vulnerary[, ]. It is used in the treatment of colds and abdominal coldness and fullness[]. A tea made from the roots is a children's sedative[]. Use of the bulb in the diet impedes internal parasites[].
Externally, the bulb can be made into a poultice to drain pus from sores, boils and abscesses[].

Agroforestry Uses:

Allium species usually grow well with most plants, especially roses, carrots, beet and chamomile, but they inhibit the growth of legumes[, , ]. They are, in general, bad companions for alfalfa - each species negatively affecting the other[].
Members of this genus are rarely if ever troubled by browsing deer[].

Other Uses

The juice of the plant is used as a moth repellent. The whole plant is said to repel insects and moles[].
The plants are said to reduce or prevent white ant infestation in gardens, and in China the diluted juice is used as a treatment against aphids[].

The welsh onion is related to the cultivated onion (Allium cepa) and could be of value in breeding programmes[, ].

Propagation

Seed - sow spring in a greenhouse. The seed germinates over a wide range of temperatures, it is faster at higher temperatures[]. Prick out the seedlings into individual pots when they are large enough to handle. When well-grown, the plants should be ready to be planted out in the summer. If they are not large enough at this time, grow them on in the greenhouse for their first winter and plant them out in late spring.
Division of the plants is very easy and can be done at almost any time of the year though the spring is probably best. The divisions can be planted out straight into their permanent positions if required.