Crop type: Salad Onions
Allium fistulosum ‘Ishikura’ AGM
Common name: Bunching onion ‘Ishikura’
Crop slug: salad-onions
This Allotment Pro editorial draft summarises the cited RHS cultivar profile and its linked crop guidance. Check the sources and adjust cultivation decisions for local conditions.RHS cultivar profile
1 - Overview
‘Ishikura’ is an award-winning Japanese bunching onion with elongated, straight white stems and hollow green leaves. Its stalks do not swell into rounded bulbs and can be harvested at several stages, from slim young salad onions to more substantial bunching stems. An exceptionally long summer-to-autumn harvest can be achieved without repeated succession sowings.
Although often raised as an annual vegetable, it is botanically an evergreen perennial. Plants carried into a second year may produce dense spherical heads of greenish-white flowers on stems around 60cm tall in early to midsummer, providing interest to pollinators.
2 - Size
- Ultimate height
- 0.1–0.5 metres, with flowering stems to about 60cm
- Ultimate spread
- 0.1–0.5 metres
- Time to ultimate size
- 1–2 years
- Habit
- Clump forming
Annual rows stay narrow and upright. Give more room to plants retained as perennial clumps, especially where they will be allowed to flower.
3 - Growing conditions
- Suitable soils
- Chalk, loam or sand
- Moisture
- Moist but well drained, or well drained
- Soil pH
- Acid, alkaline or neutral
Grow in fertile, freely drained soil and maintain steady moisture during active growth. If the site has heavy clay that remains saturated in winter, use a container of free-draining compost instead of trying to overwinter plants in the ground.
4 - Position and hardiness
- Light
- Full sun
- Aspect
- South- or west-facing
- Exposure
- Sheltered
- Hardiness
- H5 — hardy in most UK locations even during severe winters
Full sun encourages strong upright stems and productive foliage. ‘Ishikura’ has useful cold tolerance, but a sheltered, well-drained site gives overwintered clumps the most reliable conditions.
5 - Colour and seasonal interest
| Season | Flowers | Foliage | Edible stems |
|---|---|---|---|
| Spring | — | Green | White and green |
| Summer | Greenish-white on second-year plants | Green | White and green |
| Autumn | — | Green | White and green |
| Winter | — | Green | — |
The crop is defined by long, straight white non-bulbing stalks transitioning into upright hollow green leaves. Second-year plants add rounded greenish-white flower heads above the clump.
6 - Botanical details
- Family
- Amaryllidaceae
- Native to Great Britain and Ireland
- No
- Foliage
- Evergreen
- Habit
- Clump forming
- Name status
- Accepted
- RHS recognition
- Award of Garden Merit and Plants for Pollinators
- Synonym
- Allium cepa ‘Ishikura’
Genus
Allium includes edible and ornamental onions, garlics and relatives with onion-scented foliage and rounded flower umbels. Allium fistulosum selections are valued for hollow leaves and elongated stems that remain straight and non-bulbing.
Safety
Alliums can be toxic to dogs and cats if eaten. Keep harvested material, thinnings and discarded leaves away from pets.
7 - How to grow
Cultivation
Grow in fertile, well-drained soil in full sun. Sow seed for an annual crop, keeping plants evenly watered during dry spells, then harvest at the stem size required from summer into autumn. The stalks can be pulled young or allowed to lengthen without developing a rounded bulb. Use containers where heavy winter clay would remain saturated.
Propagation
Propagate from seed.
Suggested locations
- Allotment or kitchen garden
- Cottage or informal garden
- Patio container
- Wildlife-friendly edible border
Pruning
No routine pruning is required. Remove old flowering stems and tired foliage from retained clumps as necessary.
Pests
May be susceptible to allium leaf miner and onion fly. Inspect leaves and stems regularly and remove affected material promptly.
Diseases
May be susceptible to onion white rot and onion downy mildew. Rotate allium crops, maintain airflow and reliable drainage, and avoid contaminated ground.