Does it need a lot of sun?

Yes, it thrives in full sun for best growth.

Can I grow it in a pot?

It grows very well in containers with good drainage.

Plant guide

Welsh onion.

Allium fistulosum

Pronounced AL-ee-um fis-tyoo-LOH-sum

Also known as Japanese bunching onion, Welsh Onion

The Welsh onion is a hardy perennial that produces hollow, blue green leaves. It is a staple in many kitchens for its mild onion flavor. You will find it grows in clumps rather than forming a large bulb.

At a glance

Care level: Easy
Plant type: Perennial herb
Light: Full sun
Indoor light: Direct sun
Water: Every 3 to 7 days
Mature size: 24 inches
Growth rate: Fast
Hardiness: USDA 5 to 9
Bloom time: Late spring to mid summer

Care

Keep the soil consistently moist but never waterlogged to encourage healthy growth. Watch for yellowing leaves which often indicate poor drainage or overwatering. Harvest the stalks regularly to keep the plant productive throughout the season.

Watering: Water when the top inch of soil feels dry to the touch.
Feeding: Apply a balanced liquid fertilizer during the active growing season.
Pruning: Trim back the tops regularly to encourage fresh growth and prevent flowering.
Repotting: Divide the clumps every couple of years to prevent overcrowding.
Soil: Well draining loamy soil
Soil pH: 6.0 to 7.0
Temperature: -25 to 35°C
Humidity: 40 to 70%
Drought tolerance: Moderate
Lifespan: Perennial, typically 3 to 5 years
Fragrance: Light
Deer and rabbits: High

Signs it needs repotting

Roots growing out of drainage holes
Water running straight through the pot
Plant growth slowing significantly

Safety

People: It is generally safe to eat, but large quantities may cause digestive upset in some people.
Pets: This plant is toxic to cats and dogs if ingested.
Children: The plant is safe for children, though the strong scent may be off putting to some.
Contact allergens: Handling the raw bulbs or leaves may cause mild skin irritation in sensitive individuals.
Airborne allergens: The pollen is not typically a major allergen.
Edibility: Ensure you correctly identify this plant as it resembles some toxic bulbous species.

How to identify it

Hollow cylindrical blue green leaves
Clumping growth habit
Lack of a distinct bulb
White or greenish white flower umbels

Height: 0.3 to 0.6m
Spread: 0.15 to 0.3m
Leaves: blue green, deciduous
Flowers: white, pale green, 2 to 5cm
Fruit: black, Summer

Problems to watch for

By symptom

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Growing it

Propagation: seed, division
When to plant: spring, autumn
Overwintering: Cut back dead foliage in late autumn. In very cold climates, apply a light layer of mulch to protect the roots.
In containers: It is excellent for containers, requiring a pot at least 15 cm deep.

Division

1. Carefully dig up a mature clump in spring.
2. Gently pull the clump apart into smaller sections.
3. Replant the sections immediately in well draining soil.

Plant these near carrots to provide natural pest protection for your vegetable patch.

Grows well with

Carrot — The strong scent of the onion helps deter carrot rust flies.
Lettuce — They grow well together without competing for space.

Keep away from

Bean — Onions can inhibit the growth of beans when planted too closely.

Similar species

Chives — They share similar growth habits and culinary uses.

Science

Family: Amaryllidaceae
Genus: Allium
Order: Asparagales
Class: Liliopsida
Native range: Central and East Asia
Conservation: This species is common and not of conservation concern.

It grows in clumps and spreads slowly, often found in open fields and meadows.

Value to wildlife: nectar source
Pollinators: bees, butterflies
Uses: culinary herb, ornamental garden border, companion planting

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Soil reaction: 6/9
Moisture: 5/9
Nutrients: 6/9
Salinity: 2/9
Light: 7/9
Temperature: 5/9

Taxonomy resolved against GBIF.

Questions people ask

Does it need a lot of sun?: Yes, it thrives in full sun for best growth.
Can I grow it in a pot?: It grows very well in containers with good drainage.

Where the name comes from

The name Allium is the Latin word for garlic, while fistulosum refers to the hollow, pipe like structure of the leaves.

Good to know

Unlike common onions, this species does not form a large bulb.
It is a perennial that can be harvested repeatedly throughout the season.
The hollow leaves are what give it the name fistulosum, meaning pipe like.
It is a key ingredient in many stir fry dishes.

Also in

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This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.