Spring Onion.

At a glance

Care level

Easy

Plant type

Perennial vegetable

Light

Full sun

Indoor light

direct

Water

Every 2 to 4 days

Mature size

30 to 60 cm tall

Growth rate

fast

Hardiness

USDA 6 to 9

Bloom time

Late spring to early summer

Care

Keep the soil consistently moist but not waterlogged to ensure tender stalks. Watch for yellowing tips which often signal the soil is drying out too much. Harvest by pulling the entire plant or cutting just above the soil line for regrowth.

Watering

Keep the soil evenly moist for the best flavor and texture.

Feeding

Use a balanced, water-soluble fertilizer once a month during the active growing season.

Pruning

Trim back any damaged or yellowing leaves to encourage fresh, new growth.

Repotting

Usually grown as an annual, so repotting is rarely needed unless growing in a permanent container.

Soil

Well-draining, rich, loamy soil

Soil pH

6.0 to 7.0

Temperature

7 to 24°C

Humidity

40 to 60%

Safety

People

The plant is generally considered non-toxic to humans when consumed as food. Large quantities might cause mild gastrointestinal upset in sensitive individuals.

Pets

This plant is toxic to cats and dogs if ingested in large quantities.

Children

The plant itself is not inherently dangerous, but small children could potentially choke on raw pieces if not properly cut.

Contact allergens

No significant contact allergens are commonly reported.

Airborne allergens

Pollen may cause respiratory irritation in individuals with allergies to the Allium family.

Edibility

While generally considered safe for consumption, always ensure proper identification and cooking, especially for wild-harvested specimens.

How to identify it

• Hollow, cylindrical green leaves
• White, non-bulbing base
• Upright, grass-like growth habit
• Small, spherical white flower clusters

Height

0.3 to 0.6m

Spread

0.1 to 0.2m

Leaves

green, evergreen

Flowers

white, 1 to 2cm

Common problems

• Onion Maggots — These fly larvae bore into the bulbs and roots, causing wilting and decay.
• Downy Mildew — Fungal disease causing purplish spots on leaves, leading to yellowing and dieback.
• Thrips — Tiny insects that rasp the leaf surface, causing silvery streaks and distorted growth.
• White Rot — A soil-borne fungal disease that causes wilting and a white, cottony growth on the base of the plant.

Growing it

Propagation

seed, division

When to plant

spring, autumn

Interplanting Allium fistulosum with vegetables like carrots and lettuce can offer mutual pest protection and improve soil conditions.

Grows well with

• Carrots — Planting onions near carrots is said to deter the carrot rust fly.
• Lettuce — Onions can help deter lettuce aphids, and lettuce provides ground cover that helps retain soil moisture around the onion roots.
• Cabbage — Onions can help repel cabbage worms and other pests that bother brassicas.
• Spinach — They have similar growing needs and benefit each other by deterring pests.

Keep away from

• Asparagus — Onions produce compounds that can stunt the growth of asparagus.
• Beans — The sulfur compounds produced by onions can inhibit the growth of certain bean varieties.
• Peas — Similar to beans, onions can negatively impact the growth of peas.

Similar species

• Common Onion — Both are alliums with edible bulbs and leaves, but Allium cepa typically forms a large bulb while Allium fistulosum does not.
• Garlic Chives — These also have edible leaves with an oniony flavor, but they are flat, not hollow, and possess a garlic undertone.
• Leek — Leeks have a milder flavor and a more substantial, thicker stalk compared to the hollow, slender stems of Allium fistulosum.

Science

Family

Amaryllidaceae

Genus

Allium

Order

Asparagales

Class

Liliopsida

Native range

East Asia

Conservation

Not of conservation concern.

It thrives in well-drained soils with ample sunlight, often found growing in disturbed areas or cultivated gardens.

Value to wildlife

nectar source, pollen source

Pollinators

bees, butterflies, moths

Uses

culinary, ornamental

Taxonomy resolved against GBIF.

Questions people ask

How do I grow Allium fistulosum?

Start seeds indoors or sow directly outdoors in well-draining soil. They prefer full sun and consistent moisture.

Can I eat the whole plant?

Yes, both the green tops and the white base are edible.

How often should I water it?

Keep the soil consistently moist, especially during dry periods, but avoid waterlogging.

Does it attract beneficial insects?

Yes, its flowers attract pollinators like bees and butterflies.

What's the difference between a bunching onion and a regular onion?

Bunching onions don't form large bulbs and are harvested for their green tops and small white bases.

Where the name comes from

The common name 'Welsh onion' is a bit of a misnomer; it likely refers to the German word 'welsche', meaning foreign or strange, rather than originating from Wales. The scientific name 'fistulosum' comes from the Latin word for 'hollow', referring to the plant's stems.

Good to know

• Also known as bunching onions or spring onions.
• It's believed to have originated in East Asia.
• The hollow stems have a mild, sweet onion flavor.
• It rarely forms bulbs, growing in clumps of upright leaves.