Calçot (Allium cepa)
2 sources cited · Verified
The short answer
- Plant
- Mid August to early October
- Site
- 6+ hours of sun, soil pH 8–8.6
- Biggest risk
- Allium white rot
In the UK, calçots go in the ground mid August to early October.
Calçots (Allium cepa) — biennial, harvested as second-year resprouts.
Timing is the decision that matters most in the UK: there are 4 separate regional sowing windows, ranging from mid August in Southern England to mid August 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 | mid August to early October |
| Midlands | mid August to early October |
| Northern England | mid August to early October |
| Scotland | mid August to early October |
Southern England - detail & sources
The Tier-1 source gives a specific replanting window (mid-August to late September) for the traditional Catalan method, with no UK-region-specific dates given by either source, so this window is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Midlands - detail & sources
The Tier-1 source gives a specific replanting window (mid-August to late September) for the traditional Catalan method, with no UK-region-specific dates given by either source, so this window is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Northern England - detail & sources
The Tier-1 source gives a specific replanting window (mid-August to late September) for the traditional Catalan method, with no UK-region-specific dates given by either source, so this window is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Scotland - detail & sources
The Tier-1 source gives a specific replanting window (mid-August to late September) for the traditional Catalan method, with no UK-region-specific dates given by either source, so this window is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Quick Facts
| Factor | Value |
|---|---|
| Soil pH | 8 - 8.6 |
| Sunlight | 6-6 hours direct sun |
| Soil texture | loamy, calcareous (Frontiers) |
| Drainage | well-drained |
| Lifecycle | biennial, harvested as second-year resprouts |
| Edible parts | blanched stem shoots |
At a Glance
Soil & Growing Conditions
Water: irrigated per traditional practice (Frontiers)
Soil pH range
Span reflects genuine variation between the cited authorities, not a single agreed figure.
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Bulb dormancy and replanting | 0 | Bulbs from the previous season are allowed to remain dormant, then replanted the following late summer (mid-August or late September), at 32,000 plants/ha, 0.3 x 0.75m spacing (Frontiers). |
| Resprouting | 3 | Each dormant bulb resprouts into between 1 and more than 25 slender floral shoots (Frontiers) -- the calcots themselves. |
| Earthing up / blanching | 3 | As shoots grow, soil is mounded around them to exclude light, keeping the base white and encouraging the shoots to elongate -- the same principle used for leeks (Specialty Produce). |
| Harvest | 8 | December (early, sharper) or February (late, sweeter, less fibrous) harvest of the blanched shoots (Frontiers). |
Harvest & Storage
When to pick: Harvested at one of two traditional windows: December for a sharper, more pungent early harvest, or February for a sweeter, less fibrous late harvest closer to the ideal calcot profile (Frontiers). Shoots are cut once earthed-up and elongated, with the blanched white base as the prized edible portion.
Diseases
Pests
Calçot, Field to Calçotada
References
-
Calcots are the immature floral stems of second-year onion resprouts, mainly from the long-day 'Blanca Tardana de Lleida' (BTL) landrace of Allium cepa L. The traditional landrace produces between 1 and more than 25 resprouts ('calcots') per onion bulb, harvested in the plant's second year of growth. Bulb onions are replanted at a density of 32,000 plants per hectare, planting pattern 0.3 x 0.75m, at two possible times: mid-August (early planting) or late September (late planting). Soil: loamy texture, calcareous, between basic and slightly alkaline (pH 8.27-8.61), low organic matter, no electrical conductivity problems recorded. Harvested at two different times: December (early harvest, higher chemical/pungency values) or February (late harvest, sweeter and less fibrous, closer to the ideal sensory profile). Each field managed by farmers using their own customary traditional cultivation techniques for fertilization, irrigation, weed control and pest management -- no standardized disease/pest data given.
-
Calcots are grown from onion bulbs allowed to remain dormant from the previous season and replanted the following late summer. As the resprouted stalks grow, they are covered with dirt (earthed up) to keep the base white and elongate the shoots -- the same blanching principle used for leeks. Favoured for a mild, sweet flavour and tender texture. Registered with an EU Protected Geographical Indication, certifying they are grown according to traditional methods from their geographical origin in Catalonia, Spain.
2 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 calçots in the UK?
In Southern England, from mid August. In Scotland, wait until mid August. 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 calçots?
Sow mid August to early October.
What soil pH do calçots need?
A pH of about 8–8.6. 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 calçots?
Our data links 1 disease and 1 pest 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.
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Last verified 2026-08-28
Where To Go From Here
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