Great Yellow Allium (Allium flavum)
1 sources cited · Verified
The short answer
- Plant
- Early March to early September
- Site
- 6+ hours of sun, soil pH 6–7.5
- Biggest risk
- Allium white rot
In the UK, great yellow alliums go in the ground early March to early September.
Great yellow alliums (Allium flavum) — bulbous herbaceous perennial.
Timing is the decision that matters most in the UK: there are 4 separate regional sowing windows, ranging from early March in Southern England to early March in Scotland.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
Regional Planting Calendar
| Region | Sow |
|---|---|
| Southern England | early March to early September |
| Midlands | early March to early September |
| Northern England | early March to early September |
| Scotland | early March to early September |
Southern England - detail & sources
The only source gives no region-specific UK dates; RHS gives a UK-wide hardiness rating (H5, hardy in most UK locations even through severe winters) with no frost-chasing urgency described for this hardy perennial, so one window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Midlands - detail & sources
The only source gives no region-specific UK dates; RHS gives a UK-wide hardiness rating (H5, hardy in most UK locations even through severe winters) with no frost-chasing urgency described for this hardy perennial, so one window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Northern England - detail & sources
The only source gives no region-specific UK dates; RHS gives a UK-wide hardiness rating (H5, hardy in most UK locations even through severe winters) with no frost-chasing urgency described for this hardy perennial, so one window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Scotland - detail & sources
The only source gives no region-specific UK dates; RHS gives a UK-wide hardiness rating (H5, hardy in most UK locations even through severe winters) with no frost-chasing urgency described for this hardy perennial, so one window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Quick Facts
| Factor | Value |
|---|---|
| Soil pH | 6 - 7.5 |
| Sunlight | 6-6 hours direct sun |
| Soil texture | chalk, loam or sand (RHS) |
| Drainage | well-drained |
| Lifecycle | bulbous herbaceous perennial |
| Edible parts | leaves, bulbs |
At a Glance
Soil & Growing Conditions
Water: moist but well-drained or well-drained (RHS)
Soil pH range
Span reflects genuine variation between the cited authorities, not a single agreed figure.
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Propagation | 0 | Sow seed when just ripe or in spring, or plant offsets carefully detached after flowering finishes (RHS). |
| Establishment | 3 | Narrow, cylindrical grey-green leaves; compact habit to about 40cm; full sun, well-drained soil, sheltered spot (RHS). |
| Flowering | 6 | Early summer: small, bell-shaped, bright yellow flowers with prominent stamens in loose umbels on slender stems; leaves wither quickly around this stage (RHS). |
| Maintenance / dieback | 9 | Remove old flowered stems and foliage; no other pruning needed (RHS). Time to maturity 2-5 years. |
Harvest & Storage
When to pick: Grown primarily as an ornamental, RHS Award of Garden Merit bulb; leaves and bulbs are edible but the plant is chiefly valued for its early-summer display of small, bell-shaped bright yellow flowers with prominent stamens.
Diseases
Pests
Great Yellow Allium, Field to Border
References
-
Hardiness H5 (hardy in most UK locations, even severe winters, -15 to -10C). Full sun; south or west-facing aspect; sheltered exposure. Soil: chalk, loam or sand; moist but well-drained or well-drained; pH acid/alkaline/neutral. Height 0.1-0.5m (40cm), spread 0-0.1m. Time to maturity 2-5 years. Small, bell-shaped, bright yellow flowers with prominent stamens in loose clusters during early summer. Narrow, cylindrical, grey-green leaves that wither quickly. Propagate by seed sown when just ripe or in spring, or by offsets carefully detached and planted after flowering finishes. PESTS: susceptible to allium leaf miner and onion fly. DISEASES: vulnerable to onion white rot and onion downy mildew -- named directly for this species, not inferred. Grow in fertile, well-drained soil in full sun; container growing recommended for heavy clay soils prone to winter saturation. Remove old flowered stems and foliage; no other pruning needed. Holds the RHS Award of Garden Merit.
1 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.
Frequently Asked Questions
When should I sow great yellow alliums in the UK?
In Southern England, from early March. In Scotland, wait until early March. Treat these as a guide rather than a fixed date — the governing rule is to sow only once frost risk has passed and temperatures are reliably warm enough.
When do I sow great yellow alliums?
Sow early March to early September.
What soil pH do great yellow alliums need?
A pH of about 6–7.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.
What problems affect great yellow alliums?
Our data links 2 diseases and 2 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.
Get the UK Garden Planner →Instant PDF download · Written for UK growing conditions
Last verified 2026-08-28
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.