Where do these planting months come from?

Each range is a stored planting window for this crop and climate. A month that is not listed has no stored window. It is not a recommendation to skip planting.

Why can the same season appear more than once?

When two sources give different months for the same season, both ranges are listed. They are not averaged, and the gap between them is not filled in.

How are grower notes different from official windows?

Farmer field notes are labelled Farmer field experience, with the month they were noted. They are not official department windows, and they are not yet verified against official sources.

When to plant Red onion in Low Country Dry Zone

When to plant Red onion in Low Country Dry Zone. Stored windows: September–November; March–April; December–January; May–June. Ranges from different sources are not averaged.

Unverified — based on Field Crops – Red onion – Sinhala, Department of Agriculture Sri Lanka, Sinhala page, accessed 2026-10-20: https://doa.gov.lk/field-crops-redonion-si/; confirm for your microclimate.

Stored planting windows

September–November
Transplant
Farmer field experience. Using 60–90 stored days. Plant in Sep, first harvest about 60–90 days later (around November–December). Plant in Nov, first harvest around January–February. Calculated from the stored day count and the planting month. It is not a separate harvest calendar.
Sinhala red-onion page: dry-zone rainfed Maha, September to November.
Unverified — based on Field Crops – Red onion – Sinhala, Department of Agriculture Sri Lanka, accessed 2026-10-20: https://doa.gov.lk/field-crops-redonion-si/; confirm for your microclimate.
March–April
Transplant
Farmer field experience. Using 60–90 stored days. Plant in Mar, first harvest about 60–90 days later (around May–June). Plant in Apr, first harvest around June–July. Calculated from the stored day count and the planting month. It is not a separate harvest calendar.
Sinhala red-onion page: dry-zone rainfed Yala, March to April.
Unverified — based on Field Crops – Red onion – Sinhala, Department of Agriculture Sri Lanka, accessed 2026-10-20: https://doa.gov.lk/field-crops-redonion-si/; confirm for your microclimate.
December–January
Transplant
Farmer field experience. Using 60–90 stored days. Plant in Dec, first harvest about 60–90 days later (around February–March). Plant in Jan, first harvest around March–April. Calculated from the stored day count and the planting month. It is not a separate harvest calendar.
Sinhala red-onion page: with extra water, Maha from December to mid-January. The grid marks December and January.
Unverified — based on Field Crops – Red onion – Sinhala, Department of Agriculture Sri Lanka, accessed 2026-10-20: https://doa.gov.lk/field-crops-redonion-si/; confirm for your microclimate.
May–June
Transplant
Farmer field experience. Using 60–90 stored days. Plant in May, first harvest about 60–90 days later (around July–August). Plant in Jun, first harvest around August–September. Calculated from the stored day count and the planting month. It is not a separate harvest calendar.
Sinhala red-onion page: irrigated Yala, May to mid-June. The grid marks May and June.
Unverified — based on Field Crops – Red onion – Sinhala, Department of Agriculture Sri Lanka, accessed 2026-10-20: https://doa.gov.lk/field-crops-redonion-si/; confirm for your microclimate.

Season ranges

Two or more season ranges are stored. They are not joined. A month is marked only when it falls inside a stored range.

Yala is stored from more than one source, and the months do not match. Yala (FAO) is Mar–Aug. Yala (National Drought Plan) is Apr–Sep. Both ranges are shown. They are not averaged.
Maha is stored from more than one source, and the months do not match. Maha (FAO) is Sep–Feb. Maha (National Drought Plan) is Oct–Mar. Both ranges are shown. They are not averaged.

Agricultural seasons

Yala (FAO): Mar–Aug (Agricultural)
Improvement of plant nutrient management for better farmer livelihood, food security and environment in Sri Lanka, J.D.H. Wijewardena, Department of Agriculture, hosted by FAO, accessed 2026-10-20: https://www.fao.org/4/ag120e/AG120E12.htm
Maha (FAO): Sep–Feb (Agricultural)
Improvement of plant nutrient management for better farmer livelihood, food security and environment in Sri Lanka, J.D.H. Wijewardena, Department of Agriculture, hosted by FAO, accessed 2026-10-20: https://www.fao.org/4/ag120e/AG120E12.htm
Yala (National Drought Plan): Apr–Sep (Agricultural)
National Drought Plan for Sri Lanka, Ministry of Environment, September 2020, accessed 2026-10-20: https://www.unccd.int/sites/default/files/country_profile_documents/NDP%20of%20Sri%20Lanka-Final%20Report-Sept%202020.pdf
Maha (National Drought Plan): Oct–Mar (Agricultural)
National Drought Plan for Sri Lanka, Ministry of Environment, September 2020, accessed 2026-10-20: https://www.unccd.int/sites/default/files/country_profile_documents/NDP%20of%20Sri%20Lanka-Final%20Report-Sept%202020.pdf

Methodology

Where do these planting months come from?: Each range is a stored planting window for this crop and climate. A month that is not listed has no stored window. It is not a recommendation to skip planting.
Why can the same season appear more than once?: When two sources give different months for the same season, both ranges are listed. They are not averaged, and the gap between them is not filled in.
How are grower notes different from official windows?: Farmer field notes are labelled Farmer field experience, with the month they were noted. They are not official department windows, and they are not yet verified against official sources.

Red onion crop page · Planting calendar for Red onion in Low Country Dry Zone