How to Grow Calçots USA

At a Glance

Quick Facts

Factor	Value
Soil texture	loamy, calcareous (Frontiers)
Drainage	well-drained
Lifecycle	biennial, harvested as second-year resprouts
Edible parts	blanched stem shoots

Soil & Growing Conditions

Water: irrigated per traditional practice (Frontiers)

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

Allium white rot

moderate

Stromatinia cepivora (syn. Sclerotium cepivorum)

Likely rather than confirmed: calcot is Allium cepa, the exact same species as the cultivated onion, which carries this disease. Neither source names a problem specific to the calcot growing method itself.

Pests

Allium leaf miner

low

Phytomyza gymnostoma

Likely rather than confirmed: calcot is Allium cepa, the exact same species as the cultivated onion, which carries this pest. Neither source names a problem specific to the calcot growing method itself.

What the research guides add

A calçot is a blanched onion shoot, and the Protected Geographical Indication description is the clearest account of how it is grown.

• The PGI calçots come exclusively from shoots of Allium bulbs of the variety Blanca Grande Tardía de Lérida. (Foods and Wines from Spain)
• The process begins when white onion seeds are sown in October, November and December. (Foods and Wines from Spain)
• As the shoots grow, the plants are earthed up to blanch the base, the part that is eaten. (Foods and Wines from Spain)
• Plant density is approximately 0.5 × 0.3 m, and 4 to 7 calçots are obtained from each bulb. (Foods and Wines from Spain)

Calçot in the USA: climate data

Dates are the median 32°F freeze dates and freeze-free days from NOAA NCEI U.S. Climate Normals 1991–2020; zones come from the USDA 2023 Plant Hardiness Zone Map (ZIP code of each city centre).

Sources for this section

• Foods and Wines from Spain (Calçot de Valls PGI): Calçot de Valls PGI

Section researched and checked on 25 October 2026 by the SoilCommander Editorial Team. How we check facts: editorial policy.

Sources

The full list of 3 sources behind this guide (Frontiers in Plant Science (peer-reviewed journal), Plants For A Future (PFAF), Specialty Produce) is in the references of our UK guide to calçots; they describe the plant itself, which is the same wherever it grows.