Allium cepa
Sunlight
Full sun. Day length critical for bulb initiation — short-day varieties bulb at 11-12 hours, long-day at 14-16 hours.
Water
350-550 mm per crop. Consistent moisture during bulb expansion. Reduce irrigation 2-3 weeks before harvest for curing.
Soil
Well-drained, fertile loam to silt loam. pH 6.0-7.0. Avoid heavy clay (causes poor bulb shape).
Temperature
Optimal 15-25°C for growth. Bulb initiation requires specific temperature × day-length interaction. Bolting (premature flowering) triggered by cold exposure.
Humidity
Low to moderate. High humidity promotes purple blotch, downy mildew, and storage rots.
Season
Cool season in tropics — 90-150 days. Sow seed or transplant during cool dry season.
Updated February 2026
Ibi ni Onion?
Ohereza ifoto kandi AI yacu imenya ubwoko hamwe n'inama zo kwita no guhinga.
Overview
Onion is the second most important vegetable crop globally after tomato, grown in virtually every country. It is essential to cuisines worldwide and is both consumed fresh and processed (dehydrated, pickled, frozen). India and China are the largest producers. Onion is one of the most profitable vegetable crops for smallholder farmers in Africa, providing high returns per unit area. The crop requires specific day-length conditions for bulbing — short-day varieties for tropical regions, long-day varieties for temperate regions. Storage onions can be kept for 3-6 months, providing year-round supply from seasonal harvests.
Plant Health
Onion is susceptible to 2 known diseases. Early detection is critical — use the CuraPlant app to scan leaves and get an instant AI diagnosis.
Cultivation Guide
Select varieties appropriate for your latitude (short-day, intermediate, or long-day)
Transplant seedlings at 6-8 weeks old when pencil-thick
Space at 15 × 10 cm on flat beds or 4 rows per 1 m raised bed
Control thrips aggressively — they vector diseases and reduce bulb size
Stop irrigation when 50% of tops have fallen over (maturity indicator)
Cure bulbs in shade with good airflow for 2-3 weeks before storage
Companion Planting
Strategic companion planting reduces pest pressure, improves pollination, and can significantly increase yields.
Climate & Regions
Active climate zones for Onion are highlighted below.
Tropical
Not typical
Subtropical
Not typical
Temperate
Not typical
Mediterranean
Not typical
Highland
Not typical
Arid / Semi-arid
Not typical
Specific Zones & Regions
Common Questions
Onion grows best during the cool season in tropics — 90-150 days. sow seed or transplant during cool dry season.. It requires optimal 15-25°c for growth. bulb initiation requires specific temperature × day-length interaction. bolting (premature flowering) triggered by cold exposure. and full sun. day length critical for bulb initiation — short-day varieties bulb at 11-12 hours, long-day at 14-16 hours.. In tropical regions with consistent warmth, it can often be grown year-round with proper irrigation.
Onion is commonly affected by Onion Purple Blotch, Downy Mildew. Regular crop monitoring, good air circulation, avoiding overhead irrigation, and using disease-resistant varieties are the most effective prevention strategies.
Onion grows best in well-drained, fertile loam to silt loam. ph 6.0-7.0. avoid heavy clay (causes poor bulb shape).. For irrigation: 350-550 mm per crop. consistent moisture during bulb expansion. reduce irrigation 2-3 weeks before harvest for curing.. Maintaining proper soil moisture without waterlogging is critical — Onion is sensitive to both drought stress and root rot from excess water.
Onion grows well alongside carrot, lettuce, tomato. These companions help repel pests, improve pollination, or provide ground cover. Avoid planting near bean, pea, which can inhibit growth or share susceptibility to the same pests and diseases.
CuraPlant
Scan any leaf with your phone and get an instant AI diagnosis, treatment guide, and prevention plan — even offline.
