Allium fistulosum (Welsh Onion (Japanese Bunching Onion))
Allium fistulosum (Welsh Onion (Japanese Bunching Onion))
Contents
Introduction & History
Welsh Onion — despite its name, it has nothing to do with Wales but everything to do with Asia, where it has been cultivated for over 2,000 years as the most important allium in Chinese, Japanese, and Korean cooking. This evergreen, non-bulbing perennial onion produces thick, hollow green stems year-round, making it the most reliable source of fresh onion flavour in any garden.
History & Origin
Native to China, cultivated there for at least 2,000 years. The most important allium in East Asian cuisine — known as 'cong' (葱) in Chinese, 'negi' in Japanese, and 'pa' in Korean. The name 'Welsh' derives from Old German 'welsche' meaning 'foreign,' not from Wales. Introduced to Europe in the 16th century. Remains far more popular in Asia than in Western gardens, where common onions dominate.
Botanical Description
Evergreen perennial forming clumps of hollow, cylindrical, dark green stems 30–60 cm tall and 1–2 cm in diameter. Unlike common onions, it does not form a pronounced bulb — the white base thickens slightly but remains essentially a straight stem. Spherical white flower heads appear on mature stems in summer. The entire plant has a clean, medium-strength onion flavour. Clumps expand steadily by tillering.
Stem: Semi-woody to woody at base • Height: 50 cm at maturity • Spread: 20 cm • Foliage: green • Flowers: white-yellow (summer)
Planting & Cultivation
Sow seed in spring (germinates in 10–14 days) or plant divisions at any time during the growing season. Space 10–15 cm apart. Full sun to partial shade, rich moist soil. Can also be started from supermarket bunching onions — place the root ends in soil and they'll regrow. Year-round harvesting means you need far fewer plants than with common onions.
| Sun exposure | Full Sun |
| Soil pH | 6.0-7.0 |
| Spacing | 20 cm |
| Seed depth | 3–6 mm (surface-sow if light-dependent germinator) |
| Water needs | Moderate |
| Soil type | Well-drained, humus-rich loam; add perlite or grit for drainage |
Cultivation Details
Rich, moist soil with regular watering. Feed monthly for the most vigorous growth. Unlike common onions, Welsh onions are perennials — they don't bolt and die after one season. Divide clumps every 2–3 years to maintain vigour. Earth up the stems (blanching) for longer white portions — the Japanese 'naga-negi' technique. In Asian market gardening, harvested by pulling entire plants or cutting to 5 cm for regrowth.
Climate & Hardiness
Very hardy — to −25°C (USDA zones 4–9). Evergreen in mild climates, dying back and regrowing in cold zones. Heat-tolerant. Handles summer conditions that cause common onions to bolt. Year-round production in zones 7+. One of the most climate-adaptable alliums.
USDA zones: 3-9
Minimum temperature: -30°C
Indoor growing: Suitable for windowsill culture with 6+ hours light
Seasonal Care
Spring: divide overcrowded clumps; sow seed. Summer: harvest regularly; remove flower stems. Autumn: continues growing. Winter: in mild zones, harvest all winter; in cold zones, dies back and regrows from the roots in spring. Minimal seasonal care needed.
Propagation
By division of existing clumps — pull apart and replant. By seed — germinates easily in 10–14 days. From supermarket bunching onions — root ends planted in soil regrow quickly. Self-sows if flower heads are left. All methods are simple and reliable.
| Method | Success rate | Time | Notes |
|---|---|---|---|
| Stem cuttings | 70–90% | 2—4 weeks | Softwood in spring, semi-ripe in summer; 8–12 cm |
| Division | 95%+ | Immediate | Split established clumps in spring or autumn |
| Seed | 50–80% | 14–28 days | Some require cold stratification; germination variable |
| Layering | 80–90% | 6–12 weeks | Pin low branch to soil; sever when rooted |
🌍 Distribution Map
Native origin: China
Diseases & Pests
Same pests as common onions — onion fly, thrips, allium leaf miner. Rust in humid conditions. Downy mildew. Generally healthier than common onions due to the perennial constitution. Crop rotation still recommended. No bulb rot issues since there's no significant bulb to rot.
Culinary Uses
Indispensable in East Asian cooking — Chinese stir-fries, Japanese ramen and yakitori, Korean pajeon (scallion pancakes). Use the white base for cooking (mellows with heat) and the green tops for fresh garnish. Makes excellent spring onion pancakes. In Japanese cuisine, thick negi stems are grilled whole. Can substitute for scallions/spring onions in any recipe. Pairs with ginger, soy sauce, sesame, garlic, and miso.
| Category | Pairing suggestions |
|---|---|
| Stock base | Mirepoix, soffritto, holy trinity |
| Salads | Raw in salads, chimichurri |
| Asian | Stir-fries, dumplings, spring onion pancakes |
| Garnish | Snipped chives on eggs, soups, potatoes |
Medicinal & Aromatherapy
Similar to other alliums — mild antimicrobial and cardiovascular benefits. Traditional Chinese medicine uses it for colds, nasal congestion, and digestive issues. The soup made from Welsh onion, ginger, and garlic is a classic Chinese cold remedy. Rich in vitamins A, C, and K.
Container & Companion Growing
Container Growing
Excellent container herb. Use 20+ cm pots with rich compost. Sun to partial shade. Water regularly. The evergreen habit means year-round production from a single pot. Cut as needed. Feed monthly. One of the best alliums for container growing — low-maintenance and always productive.
• Minimum pot size: 15–20 cm Ø, 3 L+
• Cluster 5–7 bulbs per pot for visual impact
• Use free-draining potting compost with 20–30% perlite or grit
• Ensure drainage holes; stand on pot feet to prevent waterlogging
• Feed with dilute liquid fertiliser (half-strength) every 2–3 weeks in growing season
• Indoor: Place on brightest windowsill (south-facing ideal); supplement with grow lights in winter
Companion Planting
Same allium companion benefits — deters pests from neighbouring crops. Excellent interplanted in vegetable beds for continuous onion supply. The green stems can be grown between rows of brassicas, carrots, and lettuce. Compact enough for intensive planting.
| ✓ Good companions | Carrots, Beetroot, Lettuce, Tomatoes |
| ✗ Avoid planting with | Beans, Peas, Asparagus |
Common Mistakes to Avoid
Confusing with common spring onions (which are just immature bulb onions). Not realising it's a perennial — many gardeners pull up the entire plant when they could just cut and allow regrowth. Not dividing overcrowded clumps, leading to thin, weak stems. Forgetting to use both the white and green portions for different culinary purposes.
Harvesting & Preservation
Cut individual stems at soil level or cut the entire clump to 5 cm for regrowth. Both methods work — the plant regrows from the base. Use fresh — the clean onion flavour doesn't survive drying. Chop and freeze for off-season use. In Asian cuisine, the white and green portions are used differently: white goes into cooking oil first, green is added at the end for freshness.
• Time of day: Early morning, after dew has evaporated but before intense midday heat volatilises essential oils
• Growth stage: Just before flowering, when essential oil concentration peaks. Once flowers open, the plant redirects energy from leaf production
• Season: Year-Round
• Part harvested: Leaves, Stems
• Harvest rule: Never remove more than ⅓ of the plant at once; this ensures continued vigorous regrowth
• Technique: Cut stems cleanly above a leaf node with sharp scissors or secateurs. Tearing damages tissue and invites disease
| Method | Process | Shelf life | Best for |
|---|---|---|---|
| Air drying | Tie bundles, hang upside down in warm, dark, airy space | 6–12 months | Most herbs |
| Oven / dehydrator | Spread on trays, 35–45°C until crisp | 6–12 months | Fleshy-leaved herbs |
| Freezing (whole) | Blanch 5s, ice bath, pat dry, freeze flat on tray | 6 months | Basil, chives, parsley |
| Freezing (oil cubes) | Chop fine, pack into ice cube tray, cover with olive oil | 6 months | Any culinary herb |
| Herb salt | Layer herb and coarse salt 1:4, dry and grind | 12+ months | Rosemary, thyme, sage |
| Infused vinegar | Pack jar, cover with warm vinegar, steep 2–4 weeks | 6 months | Tarragon, dill, basil |
| Infused oil | Fill jar with dried herb, cover with oil, steep 4–6 weeks | 3–6 months | Rosemary, thyme, chilli |
Frequently Asked Questions
Is it the same as a spring onion?
Not exactly. Spring onions are usually immature common onions (A. cepa) pulled young. Welsh onion (A. fistulosum) is a different species — a true perennial that never forms a large bulb. The flavour is similar but the growth habit is different. In Asian markets, bunching onions are almost always A. fistulosum.
Why is it called Welsh if it's from China?
The 'Welsh' comes from Old German 'welsche' meaning 'foreign' or 'Romance-speaking,' not from the country Wales. It was the 'foreign onion' to Germanic peoples, distinguishing it from their native bulb onions.
Can I harvest year-round?
In zones 7+ yes — it's evergreen and produces through winter. In colder zones, it dies back in winter but is one of the first plants to regrow in early spring, providing early-season green onion before anything else is ready.
Seasonal Care Calendar
🌱 Spring (Mar–May)
Water: Regular
Feeding: Regular feeding
☀️ Summer (Jun–Aug)
Water: Regular
Feeding: Regular feeding
🍂 Autumn (Sep–Nov)
Water: Moderate
Feeding: Light feeding
❄️ Winter (Dec–Feb)
Water: Light
Feeding: No feeding
The essential East Asian onion — evergreen, non-bulbing perennial with hollow green stems year-round. Hardy to −25°C (zones 4–9). The most reliable source of fresh onion flavour in any garden. Indispensable in Chinese, Japanese, and Korean cooking. Cut and regrow — the perfect low-maintenance allium.
Quick Reference: Allium fistulosum
Key Principles: Right location, well-drained soil, regular harvesting to promote growth, and appropriate winter protection for tender species.