Scallion (Bunching Onion)

Sow scallions as soon as the soil can be worked

Direct seed a quarter to a half inch deep in a two inch wide band, with rows 12 to 18 inches apart, in full sun. You can also start seed indoors four weeks ahead and set the transplants an inch apart in a two inch deep furrow, trimming the roots to a half inch and the tops to four inches first. Scallions are a cool season allium with no bulb to size up, so an early sowing puts all the leaf growth into the stalk while the weather still favors it, and brings the crop to pencil thickness before summer heat turns the stalks fibrous and drops their quality. Note that heat is not what makes an allium bolt - a prolonged spell of 40 to 50F is - so it is the overwintered stand, not the hot one, that runs the flowering risk.

Sow again in late summer to overwinter for a spring harvest

Make a second sowing in late summer. Allium fistulosum is very hardy, so this stand can be left in the ground through winter wherever the soil is well drained, then pulled the following spring long before your spring sowing is ready. Bunching onions never form a true bulb and have no dormancy to break, so an overwintered planting simply resumes growth as soon as the ground thaws and hands you the first fresh food of the year.

Give scallions about an inch of water a week

Supply roughly one inch of rain or irrigation each week and soak the bed thoroughly rather than sprinkling it daily. Water more often on sandy ground, where an inch penetrates about ten inches deep against six inches in clay. Do not leave the bed waterlogged. Alliums are shallow rooted, so they run dry within days of a hot spell, yet they are also sensitive to standing water - it is the steady middle that keeps stalks tender instead of fibrous.

Hill soil around the stems two to three weeks before pulling

Two to three weeks ahead of harvest, draw about two inches of soil up around the base of the stems to blanch them. Keeping light off the stem bases is what turns them white and tender, and two to three weeks is roughly how long that blanch takes to develop before the stalks come out of the ground.

Band nitrogen beside the row in two or three small doses

Band fertilizer in a strip alongside the row rather than broadcasting it over the bed, and split the season's nitrogen into two or three small applications instead of one large one. Aim for a soil pH of 6.0 to 6.8 and full sun. Allium roots never extend far from the plant, so broadcast fertilizer mostly lands where the crop cannot reach it, and two or three small nitrogen doses keep the supply steady instead of one flush that leaches straight past a shallow root zone.

Thin seedlings early to one plant per inch

Thin young scallions to about one plant per inch and weed gently and often while the plants are still small. Do not throw the thinnings out - they are edible as baby scallions. Scallions are thin, upright, and shallow rooted, so early in the season weeds easily outcompete them and crowded seedlings stunt each other; once the stand closes over, the plants hold their own.

Onion maggot: rotate and clean up before you sow

Site new scallions as far from last year's alliums and from any cull pile as your ground allows - a quarter mile is the commercial standard. Destroy crop debris, remove culls, and when you work the bed bury surface organic matter rather than leaving it lying on top. Watch for seedlings that yellow, wilt, and pull up easily. Onion maggots overwinter as pupae in the soil and in cull piles, and the flies lay eggs right at the base of allium plants in spring; the larvae then crawl in under the leaf sheath, so by the time the tops wilt the insect is somewhere no spray reaches and control is no longer possible.

Scout for onion thrips through hot, dry weather

Check the leaves for silvery streaking and whitish blotches, worsening to dry yellow patches and browned leaf tips. Hang yellow or white sticky traps at the edge of the bed to catch the first arrivals, and clear plant debris from the bed and the ground around it. Act on what you find early, while the thrips are still out in the open. Thrips feed down inside the leaf sheath where sprays and predators cannot follow them, and they turn over five to eight generations a year with hot, dry weather speeding every one - a population missed during a dry spell is effectively unrecoverable.

⚠ No treatment threshold has been established for onions, and insecticides reach thrips poorly once they are tucked into the sheath, so sanitation and early detection carry most of the load. Scallion leaves are the part you eat - if you do treat, use only a product whose label lists green onions and follow its pre-harvest interval.

Pull scallions once the tops are six inches tall and pencil thick

Pull green onions any time the tops are at least six inches tall and the stems are a half to one inch across. Loosen the soil with a trowel first so the plants do not snap off. Strip the discolored outer skin, trim the leaves, bunch them, and get them cool. Scallions have no bulb to size up and no die-back to wait for, so usable size is the only real signal - and because the harvested part is a living leaf, quality starts dropping the moment it is pulled unless you cool it.