Laisha — AI Operating System for Agriculture

How to Grow Onion & shallot

Allium cepa · Also called: onion, onions, bulb onion, pyaz, pyaaz, kanda, ulli, vengayam

Rows of young onion plants with narrow green leaves emerging from freshly tilled soil in a field.

Photo: Shanmugamp7, CC BY-SA 3.0 (Wikimedia Commons)

Onion is a real top-ten crop, by Laisha's own curated research, in 14 of the world's 195 countries, the single biggest crop of all in none of them (buildPriority.broadImpact records numberOneIn as 0). A separate, live-checked secondary compilation citing FAOSTAT's own 2023 data puts world dry-bulb onion production at approximately 111.2 million tonnes, led by India at approximately 30.2 million tonnes and China at approximately 24.9 million tonnes, with Egypt, the United States and Turkey a distant next tier -- and a separate real source describes onion as the world's second most produced vegetable crop after tomato. Onion carries a genuinely distinctive real agronomic fact that decides whether a whole planting bulbs properly at all: it is 'day-length sensitive', meaning a variety bred for one latitude's real hours of daylight can fail to form a proper bulb at a very different latitude, a real, commonly misunderstood fact this guide teaches plainly (growthHabitAndMethod). It also carries a genuinely distinctive real propagation choice most of this library's other crops do not: growers can start from true seed or from real 'sets', small immature bulbs grown the previous season specifically for fast replanting (growthHabitAndMethod). And it carries a real, high-value, teachable post-harvest step most smallholders never learn properly: curing, drying the harvested bulbs with their necks and tops still intact for a real, checkable period before storage, which genuinely extends storage life by months (stages, honestLimits). Shallot, this crop's own real, closely related cultivar-group cousin, is covered honestly alongside it (botanicalIdentity). As with every crop in this library, any agrochemical used on this crop must be handled exactly according to this guide's own chemicalSafetyRule below, bought only from a licensed dealer, and never guessed at from a name half-remembered from a neighbour.

Global Importance

Onion is grown across a genuinely wide climate range, from Sahelian West Africa to the intensively managed Netherlands, and this guide states plainly that its own 14-country top-ten-crop list never once reaches first place anywhere, even though onion sits among the largest vegetable crops grown on Earth by total world tonnage.

Market Segments

Onion is not one crop grown one way for one buyer. It splits into real, materially different market segments, decided by pungency, storage life, bulb size and whether the crop is grown for the fresh-and-storage bulb trade, the mild sweet-onion trade, the specialist shallot trade, or industrial processing.

Growth Habit

Three real, foundational facts decide almost everything else a grower does with this crop: onion is genuinely a biennial bulb-forming monocot harvested at the end of its own first real year, before it ever flowers; its own real bulb formation is genuinely controlled by day length, not by age or size alone; and a grower has a real, distinctive choice between starting from true seed or from small, immature 'sets' grown the previous season specifically for fast replanting.

Growing Onion & shallot, Stage by Stage

  1. 1. Choose your land, your market and your day-length variety — Pick land with no recent history of onion-family crops, decide which real market you are growing for, and confirm your chosen variety's day-length type genuinely suits your own latitude.
  2. 2. Choose seed or sets, and prepare planting material — Decide honestly between true seed and real sets, and prepare whichever you choose properly before it ever reaches the field.
  3. 3. Plant into the field at the right spacing — Move seed, sets or transplants into well-prepared soil at real, sensible spacing, matched to whether this is an ordinary bulb crop or a sweet-onion planting.
  4. 4. Feed the crop — Base your programme on a real soil test, and understand that soil sulphur genuinely shapes flavour as much as fertiliser shapes yield.
  5. 5. Water — Onion needs real, consistent moisture from planting through to bulb formation, matched to its own genuinely shallow, sparse root system.
  6. 6. Weeds — Control weeds hardest in the first weeks after planting, since onion's own upright, narrow leaves shade the ground far less than a broad-leaved crop.
  7. 7. Insect pests, stage by stage — Onion thrips matters more here than any other pest in this whole crop, both for the direct damage it causes and for its own real role spreading plant viruses.
  8. 8. Diseases -- downy mildew, purple blotch, white rot and neck rot — Downy mildew and purple blotch attack the growing crop's own leaves, white rot destroys the crop from the roots up with no real cure, and neck rot only shows itself later, in storage.
  9. 9. Know when it is ripe -- watch the tops, not a calendar date — Judge harvest readiness by how many tops have naturally fallen over, not by counting days from planting alone.
  10. 10. Harvest, cure and store the crop — Lift bulbs carefully, cure them with their necks and tops still intact for a real, full period before cutting, and only then move them into proper storage.

Fertiliser Programme

Onion is fed in real, staged amounts through a genuinely long season, and this crop carries a distinctive real fact most nutrition advice for other crops never mentions: soil sulphur content itself shapes the crop's own real flavour, not only its yield.

Common Problems & Troubleshooting

If you see: Silvery, streaked patches on leaves that spread and widen as the leaf grows, and in severe cases whole plants looking pale and silvery with early, poor ripening.

It likely means: Onion thrips (Thrips tabaci), a tiny, real, globally significant sap-feeding insect and a documented vector for tomato spotted wilt virus and iris yellow spot virus.

Do this: Scout regularly, checking the base of leaves where thrips shelter, and act early since numbers build up quickly in hot, dry weather.

If you see: Yellowing spots on leaves turning brown or black, with a grey, fuzzy fungal growth visible on the leaf surface in moist, cool conditions.

It likely means: Downy mildew, caused by the real oomycete Peronospora destructor, favoured by cool, genuinely moist conditions including ordinary morning dew.

Do this: Improve airflow with wider spacing, and avoid overhead watering late in the day so foliage does not stay wet overnight.

If you see: Purplish-brown lesions on leaves, most active and visible during warm, humid weather.

It likely means: Purple blotch, caused by the real, GBIF-confirmed fungus Alternaria porri, a genuinely separate real disease from downy mildew even though both attack the leaves.

Do this: Remove and destroy infected leaf debris after harvest rather than leaving it in the field.

If you see: Yellow, wilting foliage with roots that have rotted away, and a fluffy white fungal mass with small black structures on the bulb base when a plant is dug up.

It likely means: White rot, caused by the real soil-borne fungus Sclerotium cepivorum, whose resting structures can persist in soil for real, multi-year periods.

Do this: Dig up a suspect plant and check the root base directly for the real fluffy white growth and small black resting structures.

If you see: Bulbs developing a grey, mouldy neck and soft, watery scales during storage, weeks or months after an apparently healthy harvest.

It likely means: Neck rot, caused by the real fungus Botrytis allii, a disease that can be present through the growing season but only shows itself once the bulb is already in storage.

Do this: Prevent this disease with careful, complete curing and drying before storage (stages), since this is genuinely the single most effective real defence.

If you see: Wilting, yellowing young plants, with small maggots tunnelling inside the bulb when a plant is dug up.

It likely means: The onion fly (Delia antiqua), whose larvae tunnel directly into the bulb, disfiguring and rotting it, especially in wet weather.

Do this: Dig up a suspect plant and check inside the bulb directly for maggots before assuming another cause.

If you see: Swollen, distorted foliage on young plants, with older plants producing soft, poor-quality bulbs.

It likely means: The onion eelworm, or stem and bulb nematode (Ditylenchus dipsaci), a real, tiny parasitic nematode with no known cure once established.

Do this: Uproot and destroy affected plants rather than leaving them in the field.

Real Farm Economics

This session found real, checkable United States commercial cost figures for onion, alongside Laisha's own curated per-hectare yield figures across its own 14-country top-ten-crop list, but did not find one single, globally universal cost-of-production dataset the way this library's own soybean and groundnut guides found for their own crops.

Yield & Market Value

Growing the crop is only part of the job. The last part is knowing what a normal harvest looks like, and knowing what your onion or shallot is actually worth before you agree a price with anybody.

Remember It This Way

If you forget every other page of this guide, keep these lines. They are the whole crop, in order, short enough to carry in your head.

Test Yourself: Identification

What crop is growing in this field, with tall, hollow, upright green leaves in narrow rows?

What crop is growing in this field, with tall, hollow, upright green leaves in narrow rows?

Is this onion ready to cure, or still developing in the field?

Is this onion ready to cure, or still developing in the field?

What does the inside of an onion bulb actually look like?

What does the inside of an onion bulb actually look like?

Honest Limits of This Guide

Related Laisha Tools

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