How to Grow Bunching Onions 

Resilient, low maintenance and surprisingly productive, bunching onions are amongst the easiest vegetables that you can add to your garden. Once started you can practically forget about these unfussy plants. After harvest they die away before returning bigger and better the following year.

As well as their productivity bunching onions (Allium fistulosum) are also good companion plants, helping to deter common garden pests such as slugs. Often grown as annuals and harvested completely before reseeding the following year, you can also cultivate bunching onions as perennial vegetables.

Happy to grow in pots, planters or straight in the garden, however you choose to grow them, this complete guide to bunching onions has all the information that you need.

Bunches of fresh green onions.  

What are Bunching Onions?

Bunching onions, also known as Scallions, Spring Onions, Green Onions, Welsh or Japanese Bunching Onions are perennial non-bulbing allium plants. Whatever you call them, these plants can be identified by their production of tasty hollow green stems and small white roots.

Slower to develop are the long lasting green-white flowers. Once open, the flowers last throughout the summer months. As well as providing some ornamental interest, the flowers are also edible. However some people can find their sharp flavor a little dry.

If allowed to, long lasting flowers can emerge.

Despite the name, Welsh onion, these hardy vegetables have no direct link to Wales. In fact the plants were first cultivated in China. From there different varieties have spread across the world.

One of the oldest cultivated vegetables, Allium fistulosum plants have been used by humans as early as 200 BC, the alternative name Welsh onion originates from an old English word meaning foreign.

While the base of the stem is rounded and bulbous, unlike white onions, the main crop of the scallion is the stem, not the bulb. Onion-like bulbs do not form. Instead the plants send out tender green shoots.

The tender green shoots, often described as leaves, have a mild, onion-like flavor and are edible both raw and cooked. A plant can produce between 5 and 10 leaves at a time.

During the growing season you can treat the leaves or shoots as a cut and come again crop, harvesting what you need and allowing the plant to produce replacement leaves. .

Scallion’s habit of bunching up around the central plant stem helps the plant to conserve energy. The plants do not separate with each bulbous base in the same way that white onions do.

Scallions are tough vegetables. Typically grown as a perennial crop, you can harvest Allium fistulosum year after year. Larger types can resemble leeks while smaller varieties are more similar to chives.

Not only are these plants edible, they are also a common ingredient in Chinese medicine. Allium Fistulosum plants can help to improve metabolism, prevent cardiovascular disorders and treat colds or upper respiratory infections. Herballists also use scallions in poultices to treat infections and drain sores.

A good companion plant, you can use Allium fistulosum plants onions to deter a number of pests including moths, aphids, termites and moles.

Why are They Called Bunching Onions?

There is some confusion over why Scallions are called bunching onions. All alliums set bulbs and bunch. After all this is how bulbs develop, multiplying from the root plant of the main, parent bulb.

Usually allium bulbs are wrapped in a papery casing until they are ready to send out their own roots. Allium fistulosum plants develop in largely the same way, except they do not have a protective papery casing around the developing bulb. Instead, as soon as they are ready to multiply, they send out shoots.

When growing, you can duplicate the plant’s bunching habit by multi-sowing to create higher yields. This is ideal for plants such as Allium fistulosum that don’t mind being cramped together. If grown as a perennial crop, the plants produce one onion at a time, clumping together in the second year.

The base of the plant does not swell like a larger onion stalk.   

Are Allium Fistulosum Plants Invasive?

Perennial plants, just one sowing of Allium fistulosum plants can return year after year.

Initially developing as an individual plant, bunching onions spread by duplication. Eventually, if allowed to, the original plant is overtaken by its offspring.

Despite this spreading habit, these are not invasive plants. They are actually fairly slow to spread. If you do find that your bunching onions are outgrowing their space, simply dig them up and eat them. Even in the depths of winter the entire plant remains edible. However, it may be a little tough.

Different Types of Allium Fistulosum

There are two types of Allium Fistulosum, Welsh and Japanese. These are both grown across the world.

Despite the name, Welsh types are predominantly found in Africa. They are commonly grown for their green leaves which are used in soups, salads and stews.

Japanese types are commonly grown in Asia and tend to be thicker than the Welsh variety. A mild flavor makes them a popular ingredient in a range of dishes.

There are several cultivars available for home growers. Amongst the most popular are:

• Evergreen, a non-bulbing type that is popular for its mild flavor. Commonly used as a garnish in salads and cooked dishes, Evergreen is a low growing plant. It can take 65 to 120 days to fully mature.
• Tokyo is a long, white Japanese heirloom variety which is suitable for growing in all parts of the United States. Ideal for cooked dishes, it reaches maturity in 75 to 95 days.
• Heshiko is a hardy Japanese variety. Like Tokyo it is suitable for all growing zones and is a good overwintering type. Reaching a height of 12 to 14 inches, Heshiko matures in 60 to 120 days.

Different types of scallions.  

Most Allium fistulosum plants are hardy in USDA Zones 5 to 9. Growers in planting areas outside this range can cultivate the plants as annuals.

Starting From Seed

Growing from seed is often more affordable than buying small plants or transplants. It also enables you to choose from a wider range of varieties. In the case of bunching onions, growing from seed is pleasingly simple.

Small, black bunching onion seeds with their sharp, angular edges can be said to resemble shards of flint. Their angular shape makes them easier to handle than many other types of seed.

Don’t worry about sowing the seeds the right way up. Bunching onions have no preference. They also don’t mind if you sow them shallowly in the earth or a little deeper. Because of this the seeds can germinate at any time.

For a summer harvest, the best time to sow bunching onion seeds undercover is 5 to 6 weeks before your last predicted frost date. You can continue to sow seeds into early summer for a fall harvest.
You can also sow in late summer or early fall for a harvest the following spring.

Start the seeds in pots, undercover. 

Fill a 2 to 3 inch pot with fresh seed starting or potting soil. Make a hole no more than 1 inch deep and sow 5 to 10 seeds per hole. If all the seedlings germinate the weaker ones can be picked out as they grow.

You can also broadcast the seeds over a MIXC Seed Starting Tray filled with fresh Espoma Seed Starting Soil. Clumped together groups can be thinned out to 1 inch apart once the seedlings are established.

After sowing the seeds, fill the hole with water. There is no need to water the seeds again until they germinate. Remember, Allium fistulosum plants thrive with a little neglect. Too much attention can kill them.

Place the pots on a sunny windowsill. The temperature should average 59 to 68 ℉. Germination usually takes 2 to 4 weeks.

You can also start the seeds in a glass filled with some fresh potting soil. Sowing seeds against a glass is a great way to observe how they germinate.

The onion seed is unique in that it doesn’t sprout up towards the soil surface, instead it sprouts sideways. Once clear of the seed, the sprout splits. The roots branch downwards and the stem forms an elbow and grows upwards, forcing its way out of the soil. Children in particular love to watch the seeds germinate.

How to Transplant

Following germination, allow the seedlings to grow on until they are 3 to 4 inches tall. Then, when all risk of frost has passed, harden the seedlings off before transplanting outside. You should also harden off shop bought transplants before planting.

Harden off the delicate seedlings before transplanting into the final growing position.

Where to Plant

Allium fistulosum plants are an easy growing crop. As long as the soil is fairly loose, the plants thrive.

Bunching onions do best in a sunny position and nutrient rich soil. A soil pH of 5.5 to 7.0 is preferred but the plants tolerate most soil types.

To improve the soil before planting work in organic matter such as aged manure or compost. This gives your plants a boost and improves your yield.

You can plant your seedlings in either full sun or partial shade.

If you are growing in a crop rotation system, add some eggshells to the soil surface. This provides a slow release of phosphorus which boots root development. Adding eggshells to the soil also helps to replace the phosphorus that the plants use up as they grow.

https://www.youtube.com/watch?v=8MXs9f0zJbo

How to Plant

Water the soil gently before transplanting.

Remove the transplant from its pot and dip the bottom of the roots lighty in water or a diluted liquid fertilizer. This helps the plant to settle into its new growing position.

Make a hole in the soil that is large enough to hold the transplant. It doesn’t have to be too deep. Aim to plant so that the top of the roots sit just below soil level.

Bunching onions are closely related to leeks. Like growing leeks, the sweet white base is created by depriving the base of the stem of light. Planting slightly deeper encourages a larger sweet, white section to develop. Planting as deeply as possible, not covering the entire plant, also helps to protect the crop from birds and wildlife.

Space the rows 3 to 4 inches apart. Different types of scallion have different spacing requirements. Check the information on the seed packet before planting to ensure that you space the plants out correctly.

If you are unsure, bear in mind that there should be enough space between the crops to hoe or weed without disturbing the plants. Bunching onions are not the most effective ground cover plants so weeds are sure to emerge.

Spacing the plants out gives them room to grow.  

Growing in Pots

You can also grow bunching onions in pots.

Your chosen pot should be at least 8 inches wide and deep. A good mid sized pot with lots of drainage holes in the bottom is ideal.

Fill the pot with well draining potting soil. Make a hole in the center large enough to hold the transplant and plant. Firm down the soil and water well.

Caring for Bunching Onions

Wherever you chose to grow the plants, bunching onions are both resilient and low maintenance. The plants happily grow in most soil conditions.

As your bunching onions grow, why not try hilling them? This is the process of mounding the soil up a couple of inches every few weeks. This forces the plant to grow taller and creates a longer blanched stem. Hilling not only creates a longer edible stem, it also produces longer, edible leaves.

Covering the base of the stem as the plant grows, grows the leaves and blanched stem.

When to Water

Water the plants regularly. Even though established plants can tolerate drought, watering regularly helps to promote healthy growth and flavor.

Be careful not to overwater the plants and flood the soil. Soggy soils can lead to plants developing issues such as root rot. A soil moisture sensor can help you to determine the best time to water.

When to Fertilize

Apply a liquid plant fertilizer such as a comfrey tea or fish fertilizer once every 2 to 4 weeks.

You can make a comfrey tea fertilizer by cutting comfrey leaves and placing them in a 5 gallon bucket of water. Allow the leaves to steep for a few days and strain. The solution can now be decanted into a watering can and watered onto your bunching onions.

Be warned, comfrey tea has a strong aroma.

Comfrey leaves can be used to make a potent fertilizer.  

You can either grow a comfrey plant yourself or purchase a comfrey tea fertilizer from garden stores and plant nurseries. This is often more potent because it has extra nutrients added to it.

Weeding and Pruning

Regularly weed the soil around the plants. A thick layer of mulch can also be applied to deter weeds. This has the added bonus of keeping the soil moist.

Unless you want the plants to flower or to harvest the seeds, remove the flower heads as and when they form.

Keep the soil around the plants weed free.  

Winter Protection

In the fall, apply a thick layer of mulch around the plants. This helps to protect your bunching onions from the cold weather. It also stimulates the earlier production of next year’s crop. Remember to remove the protective mulch in the spring once the temperature and soil has warmed up.

Most types are frost hardy so there is no need to offer further protection.

Companion Planting

The process of growing mutually beneficial plants together to boost productivity and yield, Allium fistulosum is a useful companion plant. Like other allium plants they can be grown alongside carrots. Here the aroma of the allium plant deters the destructive carrot fly.

A wall of bunching onions, or other alliums, can also be planted around leafy greens such as lettuce plants to deter slugs.

Rows of alliums are good pest deterrents. 

Planting bunching onions in between rows of other vegetables such as lettuce or herbs like lemon balm not only benefits the leafy greens, it also reduces the amount of garden maintenance you need to do.

The roots of the leafy greens grow at a different level to your bunching onion roots. This means that the two plants take their nutrients from different levels of the soil. Leafy greens also cover more of the soil than the taller, bunching onions meaning that they deter weed growth.

You can also grow bunching onions alongside winter savory cabbage and chamomile. The bunching onion does not impact on the flavor of the other two plants while the chamomile helps to boost the essential oils and flavor of the plants.

Finally, leeks are another good companion plant choice because they deter onion fly. The larvae of this destructive pest can destroy allium crops.

Dividing Established Plants

An established bunching onion is easy to divide. Simply dig up the clump, being careful not to damage the entire root system. Split the clump of root ends into sections. These can then be planted on as individual plants or given to friends and fellow plant lovers.

Best done in the spring, you can split or divide bunching onions at any time of year.

https://www.youtube.com/watch?v=tG8szi_Qefs

How to Harvest

A straightforward process, simply lift the plants as and when you want to eat them. You can also cut off the leaves with garden scissors as and when needed throughout the growing season.

Treat the leaves of the bunching onions like chives. Best used fresh, the leaves can be used in salads, stir fries, soups, salads and sandwiches.

Greens can be treated as a cut and come again crop.

After harvest, the leaves quickly grow back. This means that you can harvest the same plant several times during the same growing season.

Smaller types of bunching onion are typically ready for harvest 4 to 5 weeks after planting out. Larger varieties require 8 to 9 weeks of steady growth before they are ready to harvest.

As a guide, if you sow the seeds in February you can plant out in April and harvest bunching onions anytime from June to September, depending on the variety you are growing.

For perennial bunching onions growers who experience mild winters you can begin harvesting as early as the spring.

Harvesting the Plants

Start to harvest your bunching onion plants as soon as they reach 4 to 6 inches tall. If you can wait until the plants are a little taller you get maximum flavor out of the plants.

Typically bunching onions are ready for harvest around 8 to 10 weeks after sowing or transplanting. At this stage the stalk is thin and white at the base. Do not allow the stalk to exceed 1 inch in thickness. The thicker the stalk the weaker the flavor.

In the first year, wait until midsummer before you start to harvest the plants. Be careful not to overharvest young plants. This gives them an opportunity to develop a strong root system which can reliably produce good harvests over the next few years.

To harvest, simply pull the onion from the ground. Remember to leave one or two bunching onions in the ground to provide next year’s crop.

If you are practicing crop rotation, lift the entire crop and move a few plants to the new planting bed. Each onion plant forms its own bunch the following year.

https://www.youtube.com/watch?v=7VANY712nnc 

Preserving Bunching Onions

If not used quickly, the foliage starts to wilt.

The best way to keep the crop fresh is to store them in a plastic bag before placing them in the crisper drawer of the refrigerator. This should keep them fresh for 10 to 14 days

You can also freeze the greens. This can be done by washing and drying the greens before chopping them up into rings as thick as you desire. There is no need to blanch the greens before freezing. Once cut up the greens can be packed into small freezer bags or containers and placed in the freezer.

Dice up the stems for longer term storage.

Finally you can dry the greens. This is a great option for storing a large crop. An added bonus is that the dried greens take up relatively little room. Simply wash and chop before placing in a dehydrator. You can also spread out the greens on a baking tray and place in the oven. Dry on the lowest heat possible.

Common Bunching Onions Problems

This is a low maintenance plant that rarely experiences any serious problems. Many pests avoid allium plants because they dislike both the smell and the taste. In fact you can even use the plants to protect your leafy greens from herbivores such as rabbits.

The light green stem and foliage of a healthy plant.  

Allium leaf miners are small flies that lay eggs on allium leaves. After hatching the pests can eat their way through the plant and down to the root system. They can also cause white spots to form on the leaf tips.

Causing further damage, the wounds created by allium leaf miners can also become rotten with fungi or bacteria, destroying your plant. Once established on a plant, there is little you can do. Instead protect your crops by covering them with POYEE Floating Row Covers.

Thrips can create blotchy streaks on the top of your plants and cause leaves to become deformed. If you notice thrips on your bunching onions, wash them off with a strong blast from the garden hose. You can also treat the affected leaves with an application of insecticidal soap.

Onion white rot is a soil borne fungus which affects all members of the allium plant family. Causing white mold to form on the base of the root system, crop rotation can reduce the spread of the disease but it may still occur. Onion white rot has been known to live in the soil for up to 20 years. If your soil becomes infected, try planting your alliums in raised beds or planters.

Some diseases may affect the root system.  

Downy mildew is an unsightly issue which causes fuzzy growth to form on the leaves. It can also cause the leaves to turn brown or yellow. Eventually the plants fail.

Cut away and destroy any affected leaves. If the entire plant is affected this should be lifted and destroyed. Do not place the diseased plant on the compost heap.

You can prevent downy mildew from forming by not overwatering the plants. Additionally, avoid overwatering in the evening. This can artificially raise humidity levels around the plants. It can also cause the leaves to remain wet throughout the night. Both of these conditions are ripe breeding grounds for downy mildew.

Adopting a simple crop rotation system can also help to prevent downy mildew from establishing itself in the garden. If your soil does become infected avoid re-planting the same plant in that position for a few years.

Botrytis leaf blight is a common foliar disease. Causing leaf tips to wilt and die back, this disease also causes white spots to form on the foliage. Wet weather can cause the sports to quickly germinate and spread.

Again affected plants should be lifted and destroyed. Weeding the soil around your plants and being careful not to overwater or over fertilize helps to prevent the issue. Adopting a simple crop rotation system can also help to prevent botrytis leaf blight.

Low maintenance and easy to grow, bunching onions are a reliable addition to the garden. Practically thriving on neglect, leaving a few onions in the ground each year enables you to enjoy fresh onions year after year.