It's hard to imagine a kitchen without some members of the allium family. From regular onions through leeks to garlic and chives, the distinctive genus is as varied as it is versatile. One of the easiest of this family to grow at home is bunching onions (Allium fistulosum).
Even though they’re widely used, Australians just can’t agree on what to call bunching onions. They’re commonly called shallots or spring onions, but are also known as scallions, Welsh onions or Japanese leeks. Genuine spring onions are in fact immature seedlings of the regular onion, or Allium cepa, harvested before the characteristic onion bulb has formed. In contrast, the bunching onion species will never grow a bulb of any noticeable size, even at full maturity.
Neither are bunching onions actually shallots, at least as shallots are most widely described across the world. It's not known why some areas confuse the two terms, but it's important to be aware that if you see a recipe calling for shallots, you'll probably want a smaller cultivar of a regular onion rather than the different Welsh bunching variety.
What's Special About Bunching Onions?
There are three main things that mark bunching onions out from regular onions or spring onions. First, as mentioned, there is no bulb that forms at the base. Instead, the plant puts out multiple tender green shoots, usually between five and ten per plant. These stems resemble spring onions, with their white lower parts and green leafy uppers, although the flavour is a little milder. And just like spring onions they can be eaten both raw and cooked.
Secondly, bunching onions are a perennial plant. This means they can provide harvests year after year if you grow them in relatively frost-free areas, unlike regular onions which follow a two-year biennial cycle.
And lastly, bunching onions can be treated as a 'cut and come again' crop, with individual stems harvested as needed before growing back in a surprisingly short time.
All this makes bunching onions a highly versatile crop, and what's more they're also one of the easiest alliums to grow from seed. Here's what to do.
Soil and Sun Preferences
Bunching onions are a compact plant with a typical spread of 10-50cm and a height of 30-100cm, so are ideal for filling a small space in your veggie patch. And for even more versatility, they can also be grown singly in pots, as long as they’re at least 20cm wide.
Bunching onions need a moist but well-draining soil, preferably with a slightly acidic pH of between 5.5 and 7. They're happiest in full sun, but will tolerate partial shade if necessary, although with slower growth and reduced cropping.
Before sowing or planting, enrich the soil by digging in a few centimetres of rotted manure or garden compost. In most soils this will remove the need for any further feeding for the rest of the growing season.
Sowing the Seeds
Thanks to their speedy growth and tolerance of a wide range of conditions, bunching onions can be sown in autumn, winter and spring, so long as hard frosts are avoided. However, with an ideal germination temperature of 15-25°C it's best to avoid sowing in full summer heat.
The tiny seeds can be sown direct in rows 30cm apart, or in punnets or seed trays for later transplanting. In either case, sprinkle the seeds sparingly onto the surface and gently cover with around 5mm of light compost or soil. Water extremely gently, preferably using a mister, to avoid washing the seeds away. Continue the careful watering until the seedlings are established, keeping the soil moist at all times.
Germination usually takes 7-10 days. If sown in punnets or trays, the seedlings should be ready for hardening off and transplanting when they reach 10-15cm in height, or after around four weeks.
After germination, thin the seedlings to 3cm apart in each row or one per pot, not forgetting that the delicate thinnings are delicious in salads or stir fries.
For a good balance between white stem bases and green leaves, simply let the plants grow. However, bunching onions can also take a leaf from the leek-growing book. Hilling up the soil around the bases as they grow will produce thicker, whiter, blanched stems, taking the plant's final character nearer to spring onions than chives.
These onions require little further care and attention apart from consistent watering and keeping on top of weeds. Feeding isn't usually necessary when grown as an annual in enriched soil, although container-grown crops may benefit from a monthly feed with a general purpose fertiliser.
For the first month or two after sowing, remove any early flowers as they form to direct more growth into the root systems. Once the onions have reached the harvest stage then leaving the flowers on the plants will be welcomed by bees and other pollinating insects, thanks to the high nectar levels produced over a fairly long period.
How to Harvest Bunching Onions
You can usually start harvesting bunching onions around 60 days after germination, but wait until the green leaves are at least 30cm long. Cut off individual stems as required at ground level, and they'll grow back quickly and repeatedly to extend the harvest.
Alternatively, harvest the entire plant by loosening the soil around the base with a fork and lifting the whole clump of stems. Bunching onions should be eaten as fresh as possible or stored in the fridge, as they quickly wilt at room temperature.
In cold climates, if you still have plants left at the end of the harvest season and want to grow them on as perennials, simply cut back to ground level and cover with a thick organic mulch. Plants should survive through to spring in all but the coolest climates.
Pests, Diseases and Other Common Problems
Bunching onions are relatively resistant to both disease and pests, and are often used as companion plants for tomatoes to deter aphids. Indeed, older, coarser leaves are reputed to make a great aphid and spider mite repellent when chopped up and steeped in water to make a spray.
Aphids can be a problem on tender young growth. At the first sign of an infestation, treat with a spray of horticultural soap and water, or if you have older bunching onion plants around, try the spray made from mature leaves.
And as always, slugs and snails can be a danger with young seedlings, so take your usual precautions including beer traps, nighttime inspections, or organic pellets.
Apart from those two common pests, the main thing to avoid is a lack of water. The plants themselves will survive drought fairly well, but the quality and amount of the stem harvest will be affected if the soil is allowed to stay dry for too long.
One last potential problem to look out for is onion white rot. This is a soil-borne fungal infection that covers the roots with small white nodules and badly affects growth. Unfortunately, there's little that can be done for infected soils, but if you've seen this problem on other members of the onion family in your patch you can expect to encounter it with bunching onions too.
Bunching onions’ versatility, easy growth and generous harvests make them a worthwhile addition to any home veggie patch.