How to Grow Spring onion

Allium fistulosum · Also called: Spring onion & green shallot, Welsh onion, Bunching onion, Scallion, Green onion, Negi, Pa, Cong

A clump of spring onions growing in bare soil, with several thick hollow green leaves rising together from one base, and round white flower heads on tall stalks above them, each stalk carrying a swelling below the head.

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

Spring onion is the quickest cash crop most growers can put in the ground. Green onions are sold fresh by the bunch, they can be cut sixty to eighty days after sowing, and a clump that is cut rather than pulled grows back and can be cut again. In China, Japan and Korea it is the everyday onion of the kitchen rather than a garnish, and China grows far more of it than anybody else. It is hardier than the common onion and stands through frost and snow, so in cold places it is the green vegetable still standing when nothing else is. Its weakness is the other side of its strength: it is sold fresh and wilts within days, so the market has to be arranged before the knife comes out.

Growing Spring onion, Stage by Stage

1. Get the land ready — Choose loose soil that drains, check what grew there before, and work in old manure, because this crop is shallow-rooted and greedy for both water and food.
2. Choose your seed or planting material — You can start from seed, from seedlings, or fastest of all by splitting a clump somebody already has.
3. Plant it out — Sow shallow or set divisions in rows close together, and plant in the cool part of the day.
4. Water — Keep the soil steadily damp and never let it dry out, because shallow roots and constant leaf growth leave no reserve to draw on.
5. Weeds, feeding and earthing up — Weed often because this crop cannot shade anything out, feed lightly and repeatedly, and draw soil up the shank to lengthen the white part buyers pay for.
6. Watch for trouble — The damage that matters is leaf disease in wet weather, thrips in dry weather, and the soil rot you cannot cure.
7. Harvest — Cut or lift about two months after sowing, take it in the cool of the morning, and cut rather than pull if you want the clump to keep giving.
8. Wash, bunch and sell the same day — Wash, trim, tie into even bunches and move the crop today, because this is the one vegetable in the library with no storage at all.
9. Keep the bed going, and save your own planting material — Split the clumps every year or two and keep a few plants for seed, so that you never have to buy planting material again.

Common Problems & Troubleshooting

If you see: Plants that grow well, make plenty of green leaf and a thickened white base, but never swell into a round onion however long you leave them.

It likely means: Nothing is wrong. The true spring onion is a different species from the common onion and does not make a bulb at any age.

Do this: Harvest it as a green onion for the white shank and the leaf, which is what it is for.

If you see: A round white flower head pushing up on a tall stalk, and the stalk below it going hard and hollow so that the plant is no longer good to eat.

It likely means: The plant has flowered, which it does in its second season or after a cold spell. A flowered stalk is tough and will not sell.

Do this: Harvest the bed before the flower stalks come up, watching for the swelling at the top of a leaf that comes before them.

If you see: Pale silvery streaks and small flecks along the leaves, worst in hot dry weather, with tiny slender insects down in the crease where leaves meet.

It likely means: Thrips. They feed inside the folds of the leaves and their damage shows as silver streaking rather than as holes.

Do this: Keep the crop watered, because the damage is always worst on a bed that has been allowed to dry out.

If you see: Grey, purple or brownish patches on the leaves after wet weather, often with a paler ring around them, and leaves dying back from the tip.

It likely means: One of the leaf diseases of the onion family, which spread in warm wet weather and in crowded beds where the leaves stay wet.

Do this: Water at the base rather than over the leaves, and water in the morning so that any wet leaves dry before evening.

If you see: Plants yellowing and collapsing in patches, lifting out of the ground with almost no roots, and a white fluffy growth with small black specks on the rotted base.

It likely means: White rot, the most serious soil disease of this family. It survives in the soil for many years and there is no cure for infected ground.

Do this: Pull out affected plants with the soil around them, carry them off the field and destroy them, and never compost them.

If you see: An established clump making many shoots that are all thin and spindly, none of them thick enough to make a decent bunch.

It likely means: The clump is overcrowded, underfed, or both. Each plant makes new shoots beside itself, and after a season or two they compete with each other.

Do this: Lift and split the clumps into single shoots and replant them spaced out in fresh ground.

If you see: Bunches that looked well when cut arriving at the market limp, with soft yellowing tops, and fetching far less than you expected.

It likely means: The crop was cut in the heat, or held too long, or carried uncovered. Green onions have no storage life at all.

Do this: Cut in the cool of early morning and never in the heat of the day.

Yield & Market Value

Growing the crop is only part of the job. The last part is knowing what a normal harvest looks like where you are, and knowing what your bunches are 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.

It is not the common onion. It never makes a round bulb.
Never after onion, garlic, leek or chive. The rot stays for years.
Split a clump and you are cutting in three weeks.
Keep it damp always. Shallow roots reach nothing deeper.
Draw soil up the base. The white part is what you are paid for.
Feed little and often, because you are cutting it again and again.
Cut rather than pull, and the clump grows back for you.
Harvest before the round flower head, or the stalk goes hollow.
Cut in the cool of the morning. Heat wilts it within the hour.
Sell it the same day. This crop has no storage at all.

Test Yourself: Identification

Why has one plant turned into a whole clump of shoots from a single base?

When is this crop ready, if it never makes anything underground to feel for?

A round white ball has come up on a tall stalk. Is the plant still worth cutting?

Honest Limits of This Guide

Green onions are sold fresh and by the bunch, and bunch sizes differ enormously between countries and even between markets in one district. This guide therefore talks about even bunches rather than giving a weight, and gives timings in days and seasons rather than in months, because a number that is right in one market or one calendar month is misleading in the next.
This guide covers the true spring onion, Allium fistulosum, which lives for years and never bulbs. A great deal of what is sold as spring onion in markets is common onion pulled young, which is a different plant that behaves differently in the ground, and the two are often not distinguished when seed is sold.
Very little is registered for use on a crop that is cut and eaten within days, and what is registered differs by country. This guide therefore concentrates on spacing, watering habit and clearing away dead leaf, which are what actually control the leaf diseases, and says to ask a licensed dealer rather than naming any product.
Yield figures for green onions are unusually unreliable, because some growers cut a bed several times and others lift it once, and national statistics do not always separate the two. Treat every number here as a rough idea of scale.

Sources

GBIF Backbone Taxonomy species-match record for Allium fistulosum L. — Global Biodiversity Information Facility (GBIF), Copenhagen (source)
EPPO Global Database — Allium fistulosum (EPPO code ALLFI) — European and Mediterranean Plant Protection Organization (EPPO), Paris (source)
FAOSTAT crops and livestock products — production data for onions and shallots, green — Food and Agriculture Organization of the United Nations (FAO), Rome (source)
Allium fistulosum (Welsh onion) — CABI Compendium datasheet — CABI, Wallingford (source)

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