(Editor's Note: This article was originally published on March 16, 2009.)
First I'd like to settle on a name for what we're talking about. Some call them spring onions, because they can simply be the spring-harvested members of your main onion crop. Some refer to them as green onions, and the tops are green and edible. The descriptives Japanese, bunching, Welsh, and multiplier are also used for members of the onion family known as Allium fistulosum that never do form big bulbs like the standard, edible, bulbing Allium cepa. Scallion is the name I see in the grocery store, so let's talk about growing scallions.
Scallions from sets--very easy
I can't resist bulk onion sets in big barrels at the farm store. Those instant onions are just so easy to pop in the ground. Using sets, I can produce scallions in almost any small spot that I can keep weed free and watered for a few weeks. Yes, these onion sets are sold for producing bulb onions, but there's no harm in pulling them early as spring onions to chop for your scrambled eggs or nachos. Rodale's Encyclopedia says that a half-inch diameter is the best size set to buy. The smallest are just runts and the biggest onion sets are more likely to put up a flower stalk. Then again, you could try for an onion flower head or two so you can harvest seed for next year's crop.
Cold-tolerant and growing best before the heat of summer, plant onion sets early. Begin planting sets anytime in the month before your final spring frost. Onions like an organic soil, good fertility and adequate steady moisture. Press the onion sets an inch or so into the soil with the pointier end towards the sky but buried. I'll venture to say that almost any garden can provide a suitable spot for green onions. Scallions will be ready for harvest within a few weeks while the weather is still relatively cool. I like my scallions thin, straight and mild.
Scallions from seed--longer harvest season, more varieties
Real scallion lovers can take scallion culture to the next level by acquiring seed of one of the cultivars of Allium fistulosum. This bunching species never forms a large bulb; rather the young onions simply grow into beautiful and tasty scallions. Some are said to be perennial and will self-divide if kept year to year. Scallion variety seed may be lumped in with regular onions, or in an "oriental vegetable" section, if you don't see them listed as scallions. You'll have numerous seed choices if you look through Plantfiles and click on the links to vendors selling each variety.
At left, a lovely clump of 'Crimson Forest'.
At right, beautifully blanched stalks of 'Tokyo Long White'
Both pictures provided by rebecca101 to PlantFiles.
Scallion seed can be planted in early spring with other cool season crops like potatos and green peas, or later in spring as well. Like all onions, scallions prefer a sunny, weed-free, amply watered garden with good organic soil. Sow the scallion seed a half inch deep and watch for thin green shoots in a week or two. Scallions can grow closely; keep them just an inch apart. Even earlier scallions are grown from seed started indoors about two months before your outside planting date.
The perennial possibilities of scallions
Some cultivars of bunching onions may be perennial for most gardeners. Many of the "evergreen" cultivars are described as perennial and liable to multiply from year to year. If a perennial type is what you seek, be sure to look for that feature while choosing seeds. Seed supplier Southern Exposure Seed Exchange says that bunching onions are cold hardy but won't withstand severe freeze. If in doubt, move your perennial scallion bunches to a sheltered spot for the winter and replant when weather moderates. Harvest green onions from your perennial bunches whenever you like; divide the clumps if they become large and thick. My sister gifted me with a large bunch of undetermined variety which multiplies every year in her Florida garden. I haven't had enough experience with it to tell you how that one performs through Maryland winters. On the other hand, when I planted cultivar "HeShiKo" I managed to keep one lonely survivor. For me it's a flowering perennial, never offsetting but presenting me with one or two flowers a year from which I gather seed.
Scallions in cooking
If you've read this far, I suppose you already have an idea what you'll do with your scallions. Beyond the fun of easy growing, scallions lend a crisp fresh accent to spring dinners. While researching for this article, I read a tempting suggestion: baste scallions with olive oil and grill them. I plan to add some scallions to my dishes of roasted asparagus this April. Mom likes to peel a few for her lunch plate. The teenagers will be chopping scallions to sprinkle on tacos, or into their experiments with Asian style cooking. I might try to recreate the super veggie cream cheese I've had at The Bagel Club in Glen Burnie, Maryland: cream cheese freshly hand-mixed with finely chopped scallions, grated carrots and perhaps some secret ingredients I'll have to puzzle out. Best of luck growing your scallions this spring. I'm sure you'll enjoy eating them!