Do bunching onions multiply? Only if they’re real bunching onions. Confused? Read this post and I’ll set you straight on everything you need to know about growing and multiplying bunching onions.
Do Bunching Onions Multiply?
If you grow true bunching onions, then yes, they’ll multiply. But the onions we often call bunching onions aren’t really bunching onions at all. And that’s where the confusion comes in.
Puzzling over bunching onions that don’t multiply is fairly common in gardening groups and forums. The reason growers have “bunching onions” that stubbornly refuse to multiply, is they aren’t bunching onions in the first place!
The problem exists because bunching onion has become a catch-all term for slender, immature onions.
Green onions, scallions, spring onions, bunching onions, and ciboule; these are all used interchangeably. That’s fine when we’re at the grocery store, but sloppy terminology leads to disappointment in the vegetable garden.
Seed sellers add to the confusion when they describe non-bunching varieties as bunching onions.
The Difference Between Green Onions & Bunching Onions
The onions commonly sold as green onions, bunching onions and spring onions are simply immature bulbing onions. These onions can be any one of the numerous bulbing onion varieties from the “Common onion” family (Allium cepa).
All Allium cepa onions go through an early growth stage which produces, long, slender stems before increasing summer day length triggers bulb formation.
These onions can be grown in clumps and harvested as young onion stalks, and it’s these onions that are usually sold in the supermarket as green onions, spring onions, bunching onions, or scallions.
They don’t multiply. To get a bunch of onions from Allium cepa, you have to sow multiple seeds in each growing spot. Allium cepa varieties are annual vegetables, so to get repeated harvests, you need to sow more seeds or plant new sets.
Bunching Onions Are Perennials
True bunching onions are perennial plants. They multiply readily and will continue to grow year after year, if you look after them properly. Harvested stems make great salad onions, and the leaves offer an alternative to chives.
The bunching onion is properly known as the Welsh onion. Its botanical name is Allium fistulosum.
Curiously though, the Welsh onion isn’t from Wales. First introduced to Europe in the Middle Ages, Allium fistulosum is actually native to China where it’s been cultivated for centuries.
The misleading name comes from the word welsche, which itself derives from the Germanic walhaz. Walhaz was a general term applied to foreign things (and people) and since this plant was from distant lands, the name stuck, and eventually became anglicized as Welsh.
Today, Allium fistulosum is heavily cultivated in China, Japan, and Korea, and bunching onions are also known as Japanese bunching onions.
Check The Botanical Name When You Buy Bunching Onions
The only way to make sure you get a true bunching onion variety when you’re buying seed is to check if the variety is Allium cepa or Allium fistulosum.
Here’s a screenshot from a seed supplier to show you what I mean.
As you can see this “bunching” onion is Allium cepa which only grows a single onion. You can plant multiple seeds together to grow these as a bunch, but this variety isn’t a perennial bunching onion that will multiply.
Here’s another screenshot.
This bunching onion is Allium fistulosum. A true bunching onion.
No wonder confusion reigns!
How Do Bunching Onions Grow?
Welsh and Japanese bunching onions grow in clumps.
The clumps produce long leaves which grow to 1′ to 1’8″ (30 cm to 50 cm). The leaves are actually hollow pseudostems, and it’s this characteristic which gives this onion its botanical name – “fistulosum” means hollow.
Left to grow to their full size, bunching onions eventually bolt and produce beautiful flower heads. Bees and butterflies go nuts for the flowers, making the plants a valuable resource for your local pollinators.
To harvest bunching onions, there’s no need to wait until the leaves reach their full size, although you can certainly do that if you want to. Leaves are ready to harvest once they’re pencil thick, and about 6″ tall (15 cm).
Cut all the leaves at once, or take a few at a time, it’s up to you. Once cut, the leaves regrow in a few weeks, giving you regular harvests of tasty leaves with a mild flavor.
Alternatively, you can dig up the entire clump, remove the onions you want to use, and replant the rest.
The flower heads are edible too. Let a few of your bunching onions mature and try them out. Chop finely and mix them into a pan of scrambled eggs for a delicious and unique breakfast.
When Do Bunching Onions Multiply?
Spring-planted bunching onions multiply during their first winter. When divided the clumps will provide enough onions to grow 4 or 5 new clumps. Then as the clumps grow, they continue to make more onions.
How To Divide Bunching Onions To Get More Clumps
The wonderful thing about bunching onions is their ability to make multiple new clumps.
To divide bunching onions, all you need to do is dig up a clump using a trowel to gently lever and lift the onions out of the soil. Don’t tug on the stems, they’ll break off if you pull them.
Carefully separate the onions, taking care to avoid breaking or bending the stems, then replant each onion in a separate growing spot. Each onion will multiply, forming a new clump of bunching onions you can harvest the following year.
If you’re harvesting bunching onions by cutting the leaves, your plants will benefit from being dug up and divided every 3 or 4 years to maintain their vigor.
Do Bunching Onions Grow From Sets?
Sets are a really quick and easy way to grow bunching onions. When you plant bunching onion sets in the spring or summer, you only need to wait a few weeks to harvest your first tender shoots.
Plant bunching onion sets in spring, summer, and fall. Leave 8″ (20 cm) between sets so the onions have room to multiply and form clumps.
For spring and summer plantings, pop the bunching onion sets just below the soil surface and top each planting off with a handful of compost.
If you’re planting in the fall, set bunching onion bulbs a little deeper in the soil – 2″ to 4″ (5 cm to 10 cm), and cover with compost.
Fall plantings will produce their first harvest in late winter and remain productive until late the following spring – making these a perfect vitamin C-rich hungry gap veggie.
Once spring arrives, bunching onions swell at their base, filling out very small bulbs. Left unharvested the onions will bolt and produce flower heads.
Spring planted bunching onion bulbs can be harvested for stems and divided to grow new clumps beginning in June.
Will Bunching Onions Grow From Seed?
They certainly will! Growing vegetables from seed is the most cost-effective way to grow your plants, and when you grow bunching onions from seeds, you get a wider choice of varieties.
Growing bunching onions from seeds also gives you the ability to keep sowing seeds every couple of weeks, ensuring a steady supply of onions throughout your first season as you establish your perennial stock.
When succession sowing, make your final sowing in late summer, or early fall.
When To Sow
Bunching onions will grow from seeds sown directly in March or April (depending on your growing zone).
You can also start seeds indoors in February or March to get a head start on the season and plant them out once your risk of frost has passed.
The optimum germination temperature for bunching onion seeds is 55°F to 68°F (13°C to 20°C).
To sow indoors, use seed modules or small pots. Sow 2 or 3 seeds per module and then thin them down to the strongest seedling once the shoots emerge.
Outdoors, sow seed about 1/2″ deep (1.5 cm) in rows or any place you want a clump to grow. Leave 8″ to 12″ (20 cm to 30 cm) between each spot in the row. Place 2 or 3 seeds at each site, then thin to leave the strongest seedling.
If you’re growing multiple rows, leave 12″ (30 cm) between rows.
Harvest spring sown bunching onions from July onward. Remove flower heads as they form, so the plant can devote its energy to making a strong root system.
Best Growing Conditions For Bunching Onions
Like other alliums, bunching onions prefer a fairly neutral soil, with pH 7.0 – 7.4 being ideal.
While bunching onions prefer a neutral soil, they’ll manage in other soils, although they won’t be as productive and may be more susceptible to pest damage and diseases.
Bunching onions grow best in loose, fertile, freely draining soil. If your soil is heavy with a tendency to hold water, you’ll get better results if you plant them in raised beds.
Dig in compost before planting to ensure your onions have plenty of nutrients. For extra fertility, add a sprinkling of blood and bone meal.
Onions need plenty of sunlight to thrive and bunching onions are no exception. Plant Welsh and Japanese onions in a sheltered spot that gets full sunlight (they’ll tolerate light shade, though).
Caring For Bunching Onions
Maintain soil fertility for your onions by adding a compost mulch each year.
These onions will also benefit from an application of blood and bone meal fertilizer every 3 to 4 weeks during the growing season.
As a shallow rooted plant, bunching onions need regular watering. Adding a mulch of compost or grass clippings helps to retain soil moisture, and in dry climates, your onions will reap the benefits of a mulch layer.
Keep bunching onions weed-free. When you remove weeds, ease them out of the soil gently so you don’t disturb the onion roots. Often weeds can be clipped off with a pair of scissors or pinched out with your fingers, and then there’s no risk of uprooting any onions.
Can Bunching Onions Grow In Containers?
Bunching onions are ideal for containers. You can sow seed directly or plant sets or transplants.
Choose pots with that are a minimum of 12″ across (30 cm) and 8″ (20 cm) deep.
Use rich compost in the container, keep the onions watered, and remember to feed them as they grow with blood and bone meal fertilizer.
Do Bunching Onions Grow In Winter?
Bunching onions are extremely tolerant of cold winter temperatures. They can remain green outdoors in temperatures as low as 0°F (-17°C) which is growing zones 6 and above.
Plants benefit from a compost mulch in the fall to help protect them from colder temperatures.
In growing zones where the ground freezes, dig up your clumps of bunching onions before the freeze, divide them, and plant them in pots. Keep the pots indoors on a windowsill until spring, then replant outdoors.
Bunching Onion Varieties
Bunching onions varieties of the Allium fistulosum type include:
- Ishikura Long
- Red Beard
- Summer Isle
- White Spear
Bunching onions of the Allium fistulosum type (Welsh and Japanese bunching onions) are perennial onions that multiply and grow in clumps. Divide the clumps and replant to get more bunching onion plants every year.
Other onions can be grown in clumps, and they’re often sold as bunching onions, but these Allium cepa types are not true bunching onions. Each seed or bulb only grows one onion.
I hope this post has answered all of your questions!
Thanks for reading: Do bunching onions multiply?