Growing Guide for Spring Onions (Allium fistulosum)

Last Updated on April 15, 2024 by Real Men Sow

These perennial non-bulbing allium fistulosum are also known as Japanese bunching onions and Welsh onions. They produce delicious green stems and tiny white roots year after year. They are characterized by thick, hollow, round stems that are bright green and beautiful greenish-white flowers.

The leaves are mildly onion-flavoured and can be eaten raw or cooked. Larger varieties look similar to leeks while smaller versions resemble chives. Although the flowers have a similar sharp taste, they are also edible. However, they can be quite dry.

Spring Onions (Allium fistulosum) Planting Summary

Seed Depth

After the last frost, sow the seed in the garden or in seed trays at a depth of 5mm (1/4 inch). Cover the seed with soil lightly. It may take between 14-21 days for seedlings to emerge

Plant Spacing

Place seeds and seedlings in close proximity. The spacing between the groups of plants should be 5-10 cm (2-3 in)

Harvest Time

Harvest in 8-12 weeks. You can harvest plants as small or large as you need. To ensure a constant supply, plant in lots.

Keep in Mind

  • It thrives in full sunlight, and in a spot that is not too dry.
  • Once established in the garden, spring onions are frost-tolerant.
  • Spring Onions love deep, friable soil that is rich with organic matter.
  • As they grow, give them good feed and compost.
  • Spring Onions thrive in sandy soil, loam, and well-drained soil with a pH of 6.2-6.8.
  • Blanch Spring Onions grow by humbling the soil around them.

Growing Tips for Spring Onions (Allium fistulosum)

Apply a thick mulch layer over the plants in the fall to prepare for winter. This will help plants survive the cold and stimulate a later crop. Once the soil has warmed, remove the mulch in spring. For a continuous supply, plant in succession every 3-4 weeks! Hilling plants could be done by adding soil to them as they grow. Each addition will make it a few inches higher. This will result in longer, more edible greens as well as long, blanched stalks.

Propagation of Spring Onions (Allium fistulosum)

From Seed

Plant seeds in spring to harvest summer crops, or in summer to mature in fall or spring. Place seeds in rows of two to three inches, spacing about a quarter inch to half an inch. After the seedlings have been established, thin them to one inch apart.

From Seedlings/Transplanting

You should start seeds indoors at least five to six weeks before your last frost date. Keep the soil at a temperature between 59 and 68 degrees F. Germination will take seven to 10 days. When plants reach three to four inches in height and the risk of frost is gone, you can transplant them into your garden in rows.

Before you plant, water the soil lightly. Before planting, you can lightly dip roots in water or liquid fertilizer.


Once established, plants are easy to divide to spread them around your garden or to be shared with neighbors and friends. You can divide plants at any time, but it is best to do so in spring. Simply dig up the clump and carefully cut off the root ends. Then replant.

Harvesting Spring Onions (Allium fistulosum)

You can either pull the entire plant and eat it like green onions or you can cut off leaves as you need them throughout the growing season . The leaves will quickly grow back and can be cut several times during the growing season.

When the plants reach four to six inches tall, harvesting can be started. The stronger the flavor, the larger the plants will get! You may need to wait up to four to five months before you can harvest whole plants. This plant can be grown all year in warm climates.

Do not harvest until mid-summer the first year. Also, be sure to not over-harvest young plants so they can develop strong roots. If you plan to save seeds or use the flowers for your cooking, it is best to remove any flower heads that have formed.

Preserving Spring Onions (Allium fistulosum)

Bunching onions can be kept in your refrigerator’s crisper drawer for up to 10 day. You can freeze them easily or dry them for longer preservation.


Greens should be washed thoroughly before being dried. Then, cut them into rings of any thickness. You don’t need to blanch them before freezing. Simply put them in freezer bags, bags or glass jars. You can grab a few to use in your cooking whenever you have the need.


The greens can be dried quickly and stored for many years. Drying is also a good way to preserve a large crop. Start by washing the greens and cutting them. Then let them air dry. You can either dry them with a dehydrator, or bake them at the lowest heat setting until they are dry.

Managing Pests and Disease of Spring Onions (Allium fistulosum)

Although onions can be delicious to us, they are not very attractive to pests and rarely cause any problems. Planting alliums around garden beds’ edges is a good precaution to keep away unwanted insects and herbivores such as rabbits. There are still some pests and diseases that can sometimes strike.

Allium Leaf Miners

These tiny flies lay eggs in the leaves of allium-family plant leaves and can reach the roots. They leave little white spots at the tips of the leaves. The mines can cause the plants to become rotten by bacteria and fungi. There is nothing you can do once the miners have buried themselves into the crop.


These tiny insects cause deformity by creating blotchy streaks at the tops and leaves. To get rid of insects, spray leaves with water. A homemade insecticide soap can be used to treat each leaf.


There are many diseases that can affect crops, especially if they are weakened by insects or weather changes.

White Rot

All members of the allium family can be affected by this soil-borne fungus. Sometimes, the disease can cause white mold to develop at the root base. Crop rotation can help reduce the spread of disease. Keep in mind, however, that it may not always be possible to prevent a recurrence. White rot can live in soil for as long as 8 to 20 years.

Downy Mildew

Mildew can cause fuzzy growths on leaves that can lead to yellowing or browning and even collapse. Avoid planting infected plants, rotate crops frequently to areas that haven’t had any other allium species grow in them in recent years, and make sure you plant in well-draining earth.

Botrytis Leaf Blight

The foliar disease is when leaves develop small white spots and tips begin to wilt. All of the leaves could eventually die. The rapid spread of spores can be caused by wet weather. Rotate to areas that have not been cultivated for several years in order to eradicate any infected plants.

Real Men Sow
Real Men Sow

Hello, I’m Pete and I’m currently based in the west of Scotland, in a small place called Rosneath, where I’m exploring my garden adventures. I personally started gardening around 6 years ago and initially, I started out by growing my favorite fruits and berries, such as strawberries, Raspberries & Gooseberries. Since then I’ve added a lot of vegetables and working closely with my neighbor, it’s been a lot of fun.