How to grow green onions

This is the source of nearly every contradiction you will read about green onions, so it is worth two minutes. Three different plants are sold under overlapping names.

The true bunching onion, Allium fistulosum, never forms a bulb. It makes a straight, hollow-leaved plant with a clean white shank, it is extremely hardy, and it is perennial — clumps divide and go on for years. Japanese negi and most seed sold as “bunching onion” or “Welsh onion” are this. If you want scallions specifically, this is the plant to buy.

The ordinary bulb onion, Allium cepa, pulled young. Any onion variety can be a green onion if you pull it before it bulbs, which is why thinnings from a bulb-onion row are a free scallion crop. It is also why some of what supermarkets sell has a visible swelling at the base.

The perennial clumps — Egyptian walking onions, potato onions, chives, and various divided bunching types — which somebody gave you and which will outlive you. These need no sowing advice at all, only dividing.

The practical upshot: if a packet says bunching, expect no bulb and expect it to survive winter. If it is a named bulb onion, expect a swelling if you leave it, and pull earlier.

Sow thinly in a shallow drill, about half an inch deep, in rows a foot apart. Do not agonise over spacing — this is a crop grown deliberately crowded, and an inch apart in the row is plenty because you will be pulling every other one long before they touch.

The one thing that matters is doing it again. A single sowing gives you two good weeks and then a row of things that have got coarse and started to think about flowering. Sowing a short row every two or three weeks from early spring into late summer gives continuous supply from the same small piece of ground, and it is genuinely the only technique this crop requires.

Onion seed is short-lived — noticeably worse in its second year and largely gone by its third. If germination is patchy, suspect the seed before you suspect yourself.

The other route is transplanting. Sow thickly in a nursery patch, then lift the seedlings when they are about pencil-thick and set them out where you want them. It sounds like extra work and it is how commercial growers do it, because you can grade the plants and space them exactly. Solomon uses it to grow scallions in the wet half of the year: a nursery sowing about mid-July, transplanted an inch apart in October when the rains return, pulled through winter.

The white part is not a variety trait so much as a growing technique: shank is white because it grew in the dark. Left alone, a scallion gives you an inch or two of white. Hilled up as it grows — drawing loose soil around the stems, an inch at a time, every couple of weeks — it will give you six or eight, which is what the long Japanese negi in the picture below are.

Do it in stages and keep the soil out of the leaf joint where the leaves split away from the stem, or you will be washing grit out of the layers for the rest of its life. Loose, dry-ish soil hills better than wet.

This is optional. If you want scallions for chopping into things, the extra white is not worth the work. If you want them to grill or braise whole, it is transformative.

This is the crop's real virtue and worth stating plainly, because almost nothing else in the garden works this way. There is no head to form, no root to size, no fruit to ripen. A green onion is edible at every stage from the thinnings you pull at pencil-thickness to the coarse thing that has started to send up a flower stem. It only ever gets stronger and tougher, never inedible.

So harvest by thinning: pull every other one, use them, and let the rest take the room. The row thins itself into the plants you leave, and you never have to make a decision about timing.

You can also cut rather than pull. Take the tops an inch above the soil and a bunching onion will regrow, two or three times, though each cut is thinner than the last. For a perennial clump this is the normal way to use it.

They do not store. A scallion is at its best within a day or two of pulling and there is no technique that changes that — which is exactly why growing your own beats buying them, and why succession sowing matters more than any storage advice.

Bunching onions are properly hardy — a good deal hardier than bulb onions — and in a mild maritime winter they simply stand in the ground. A late-summer sowing gives you something to pull from November through early spring, which is the hungry part of the year for fresh green things.

Better still, stop pulling some of them. Left alone, a bunching onion divides at the base into a clump, and the clump can be lifted, split and replanted indefinitely. A row started once and divided every couple of years becomes a permanent crop that needs no seed at all. This is what people mean when they say they have had the same onions for twenty years.

The catch is spring. Overwintered plants bolt — they send up a flower stem, and the stem is tough and the plant stops making new leaf. Solomon notes flatly that scallions bolt in April. Use them up before then, or let a few flower deliberately for seed and the bees.

Onions are among the least troubled crops in a home garden, and green onions are pulled so young that most of what afflicts bulb onions never gets the chance.

Onion fly maggots tunnel into the base and are the one serious pest; rotation and a fine mesh cover deal with them, and the crop's short occupancy makes it easy to move around. Thrips cause silvery streaking on the leaves in hot dry spells and are mostly cosmetic on a crop you eat this young. Downy mildew shows as pale patches in long wet weather, which in the maritime Northwest means it is worth spacing rows where air moves rather than tucking them against a fence.

The most common actual complaint is not a pest at all: thin, weak, pale plants, which is a fertility and water problem. Onions are shallow-rooted and compete badly with weeds, so a scallion row that has been left to fend for itself in dry ground gives you exactly what it was given.