Most people don’t realise that Welsh onions aren’t actually from Wales at all. They’re native to Asia and happen to be one of the most forgiving perennial vegetables you can grow in a British garden. I’ve been cultivating these brilliant alliums in my Derbyshire plot for several seasons now, and they’ve become my go-to solution for year-round onion flavour without the fuss of replanting bulbs every spring.
What makes Welsh onions particularly suited to our climate is their cold tolerance and ability to keep producing even when other alliums have given up. Unlike their bulbing cousins, these cluster-forming perennials focus their energy on producing hollow, tubular leaves that you can harvest repeatedly from February right through to November. I’ve found them particularly useful during that tricky gap in late winter when the stored onions are sprouting and the new season’s crop hasn’t matured yet.
The other advantage, especially for those of us dealing with heavy clay soils or small growing spaces, is their adaptability. They’ll tolerate less-than-perfect conditions and grow happily in containers, raised beds, or tucked into odd corners of the vegetable patch. Let me walk you through exactly how to grow these useful plants successfully. For more on this, see our guide on from seed to sputnik: growing perfect kohlrabi at home.
How to Grow Welsh Onions
Getting started with Welsh onions requires relatively modest equipment and materials, which is part of their appeal for both new and experienced gardeners. Here’s what I recommend having to hand before you begin.
Seeds, Sets, or Divisions
You’ve got three options for starting Welsh onions. Seeds are the most economical choice and widely available from seed suppliers and garden centres. I prefer starting from seed because you get more plants for your money, though they’ll take a bit longer to reach harvestable size. Alternatively, you can purchase small plants or divisions from nurseries, which gives you a head start. The third option, and my personal favourite once you’ve got established plants, is dividing clumps from existing Welsh onions. A single clump can be split into eight or ten plantable divisions in just a few minutes.
If you’re going the seed route, look for varieties like ‘Performer’ or ‘White Lisbon Winter Hardy’, which are particularly well-suited to our climate. Some suppliers also offer red-stemmed varieties that add visual interest to the vegetable patch. You might also find from sets to harvest: your complete onion growing guide helpful.
Growing Medium and Location
Welsh onions aren’t particularly fussy about soil, but they do appreciate reasonable drainage and a sunny to partially shaded spot. I’ve grown them successfully in everything from heavy clay (amended with grit and compost) to light sandy loam. The key is adding organic matter before planting, which improves both drainage in heavy soils and moisture retention in light ones.
For container growing, any multipurpose compost will work fine. I use pots at least 20cm deep to give the roots adequate space. Regarding location, whilst they’ll tolerate some shade, you’ll get stronger growth and better flavour with at least five hours of direct sunlight daily. A spot that gets morning sun and afternoon shade works brilliantly during hot summers.
Step-by-Step Instructions
Growing Welsh onions successfully comes down to getting the basics right at each stage. Here’s how I approach it, from sowing to establishing productive clumps.
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Starting from Seed
You can sow Welsh onion seeds outdoors from March through to July, or start them under cover from February onwards. I typically do a spring sowing in March and another in July to ensure continuous supply. Prepare your soil by removing weeds and raking it to a fine tilth. Create shallow drills about 1cm deep and 20cm apart, then sow seeds thinly along each drill. Cover lightly with soil and water gently.
Germination usually takes between 10 and 21 days, depending on soil temperature. Spring sowings can be slower if the ground’s still cold, so don’t panic if nothing appears for three weeks. Once seedlings reach about 5cm tall and are easy to handle, thin them to about 15cm apart. I don’t waste the thinnings, mind you. They’re perfectly edible and lovely in salads or as a garnish.
Planting Out and Establishing
If you’re starting with purchased plants or divisions from existing clumps, spring or early autumn are the best planting times. I’ve had success with both, though autumn-planted onions tend to establish more strongly because they get the benefit of winter rainfall and don’t face immediate competition from weeds.
Dig holes slightly larger than your root ball, spacing plants 20 to 30cm apart in rows 30cm apart. This might seem generous, but remember these plants will bulk up into substantial clumps over time. Set each plant at the same depth it was growing previously, firm the soil around the roots, and water thoroughly. In my experience, newly planted Welsh onions appreciate consistent moisture for the first few weeks until their roots establish properly.
Ongoing Care and Maintenance
Once established, Welsh onions are remarkably low-maintenance. I water mine during prolonged dry spells, particularly in summer when they’re actively growing. They’re not as drought-sensitive as regular onions, but consistent moisture does improve leaf quality and flavour. A good soaking once or twice weekly is better than daily light watering, which encourages shallow rooting.
Feeding isn’t strictly necessary if you’ve incorporated compost at planting, but I do give mine a liquid feed every four to six weeks during the growing season. Any balanced fertiliser works fine. What’s more important is keeping them relatively weed-free, especially in the first year. The plants themselves will eventually form dense clumps that suppress most weeds naturally.
Harvesting Your Crop
This is where Welsh onions really shine. You can start harvesting when plants reach about 15cm tall, typically eight to ten weeks after sowing. Simply cut the leaves about 2cm above ground level using sharp scissors or secateurs. The plant will regrow from the base, giving you multiple cuts throughout the season.
I’ve found you can harvest every three to four weeks during active growth. In winter, growth slows right down, but the leaves remain available for picking. You can also harvest whole plants if you need the bulbous base for cooking, though this obviously ends that particular plant’s productivity. The flavour is milder than standard onions, with a fresh, slightly garlicky note that I particularly enjoy in stir-fries and Asian-inspired dishes.
Winter Care and Perennial Management
Welsh onions are fully hardy throughout most of the UK, though in particularly exposed locations or during severe winters, a light mulch of straw or leaf mould provides extra protection. I don’t usually bother in the Midlands, but gardeners in Scotland or exposed upland areas might find it worthwhile.
The real maintenance task comes in spring, typically March or early April. By this point, established clumps will have become congested and may be starting to flower. Dig up entire clumps with a fork, shake off excess soil, and gently tease apart individual plants. Replant the healthiest divisions 20 to 30cm apart and either compost the rest or pot them up to give away. This division process rejuvenates the plants, prevents overcrowding, and gives you plenty of stock to expand your planting or share with fellow gardeners. I do this roughly every two to three years, and it keeps the plants productive and vigorous.
Common Mistakes to Avoid
Even with such a forgiving crop, there are a few pitfalls that can reduce your success rate or lead to disappointing results. Here’s what I’ve learned, sometimes the hard way.
Overwatering and Drainage Issues
Whilst Welsh onions appreciate moisture, they absolutely detest sitting in waterlogged soil. I’ve killed more plants through excessive watering than through neglect. The symptoms are yellowing leaves and a general look of decline. If your soil is heavy clay like mine, proper preparation with added grit and organic matter is essential. In containers, ensure adequate drainage holes and don’t let pots sit in saucers of water.
The other side of this coin is assuming they’re drought-proof. They’re not. During hot, dry spells, particularly on light soils, the leaves become tough and the flavour turns harsh without regular watering. Finding that balance takes a bit of observation, but generally, if the top 5cm of soil feels dry, it’s time to water.
Letting Plants Flower Unchecked
Welsh onions will produce attractive spherical flower heads from late spring onwards if left to their own devices. Whilst these are edible and the bees love them, allowing extensive flowering diverts energy from leaf production and can make the foliage tougher and more bitter. I remove flower stems as they appear if I want to maximise harvestable leaves.
That said, I do let a few plants flower because the blooms are genuinely attractive and beneficial for pollinators. It’s about balance. If you’re growing primarily for kitchen use, be diligent about removing flower stalks. If you want some ornamental value and can spare a few plants from intensive harvesting, let some bloom.
Harvesting Too Aggressively
It’s tempting to cut plants right down to ground level, but this weakens them over time. I’ve learned to leave at least 2 to 3cm of growth above the base. This ensures the plant can regenerate quickly and maintains vigour. Similarly, avoid harvesting from the same plant more than once every three weeks during the growing season. Give them time to recover between cuts.
New gardeners sometimes harvest whole plants when they only need the leaves, which is wasteful. Unless you specifically want the small bulbous bases for a recipe, stick to cutting the foliage and leave the plant intact for continued production.
Expert Tips
After growing Welsh onions in various conditions and configurations, I’ve picked up a few techniques that have really improved my results. These aren’t essential, but they’ll help you get the most from your plants.
Succession Planting for Year-Round Supply
Rather than sowing all your seeds at once, I’ve found it better to make smaller sowings every six to eight weeks from March through July. This gives you a continuous supply of young, tender plants rather than a glut followed by a gap. I keep a row of first-year plants for tender leaves and a separate patch of established clumps for heavier harvesting. The young plants produce finer, more delicate leaves that are brilliant raw in salads, whilst the mature clumps give you bulk for cooking.
Container growing extends this strategy nicely. I keep several pots at different stages near the kitchen door, which means I can step outside and snip exactly what I need without tramping down to the vegetable patch in the rain. Welsh onions in containers need more frequent watering but are otherwise just as productive as those in the ground.
Companion Planting Benefits
I’ve had good results growing Welsh onions alongside carrots, brassicas, and lettuce. The theory is that the onion scent confuses pests like carrot fly and cabbage white butterflies, and whilst I can’t prove causation, my interplanted carrots do seem to suffer less damage. The upright habit of Welsh onions also makes efficient use of space, as they don’t cast much shade on lower-growing neighbours.
They also work well in ornamental plantings. The fine, grass-like foliage provides textural contrast, and if you allow some flowering, the purple-white pompom blooms are genuinely attractive. I’ve seen them used effectively as edging plants in cottage gardens and mixed borders, where they serve both decorative and culinary purposes.
Soil Association Organic Standards
If you’re growing organically, Welsh onions fit beautifully into that system. They rarely suffer from serious pest or disease problems, so chemical interventions aren’t necessary. I’ve never needed to spray mine with anything. The most common issue is rust, which appears as orange pustules on leaves, usually in damp conditions with poor air circulation. The solution is better spacing and removing affected leaves promptly rather than reaching for fungicides.
For organic fertility, a spring application of well-rotted manure or garden compost around established clumps provides all the nutrition they need. Alternatively, homemade comfrey or nettle liquid feeds work brilliantly and cost nothing if you’ve got these plants growing nearby.
Frequently Asked Questions
Can you grow Welsh onions in shade?
Welsh onions will tolerate partial shade better than many alliums, but they won’t thrive in deep shade. I’ve grown them successfully in spots that receive three to four hours of direct sun, particularly morning sun with afternoon shade. The plants grow more slowly in shadier conditions and produce less vigorous foliage, but they’ll still give you a worthwhile harvest. If your only available space is quite shady, they’re worth trying where regular onions would fail completely. Just adjust your expectations regarding growth rate and total yield.
How do Welsh onions differ from spring onions?
This confuses many gardeners because they look similar. Spring onions are simply immature regular onions harvested before the bulb fully develops. They’re annuals that you pull up entirely when harvesting. Welsh onions are perennials that form small clusters rather than distinct bulbs, and you can harvest the leaves repeatedly without killing the plant. The flavour is somewhat similar but Welsh onions have a slightly milder, more complex taste with hints of garlic. Spring onions give you that characteristic small white bulb, whilst Welsh onions have a very slight swelling at the base but nothing substantial.
Do Welsh onions spread invasively?
No, they’re not invasive in the problematic sense. They do multiply by division, forming increasingly larger clumps over time, but they don’t send out runners or self-seed aggressively enough to become a nuisance. I’ve grown them for several seasons and they’ve stayed exactly where I planted them, gradually increasing in size but not spreading into surrounding areas. If you let them flower and set seed, you might get a few volunteers nearby, but these are easy to spot and remove if unwanted. They’re much better behaved than something like mint or horseradish.
When is the best time to divide Welsh onions?
Early spring, typically March or early April, is ideal because the plants are just starting into active growth and will establish quickly after division. You can also divide them in early autumn, around September, which gives them time to settle in before winter. I slightly prefer spring division because you can see exactly what you’re working with and the weather is generally improving. Avoid dividing during the hottest part of summer or during winter when the plants are dormant and growth conditions are harsh. If your clumps are flowering heavily or looking congested, that’s a clear sign they’re ready for division regardless of the calendar.
What pests and diseases affect Welsh onions?
Welsh onions are remarkably trouble-free compared to other alliums. The most common issue I’ve encountered is onion white rot, though it’s far less prevalent than with bulb onions. This soil-borne fungal disease causes yellowing leaves and rotting at the base, and unfortunately there’s no cure. Affected plants must be removed and destroyed, and you shouldn’t grow alliums in that spot for at least eight years. Prevention through crop rotation is your best defence. Onion fly can occasionally be a problem, with larvae tunnelling into the base of plants, but I’ve rarely seen significant damage. Rust, appearing as orange pustules on leaves, sometimes occurs in damp conditions but is mainly cosmetic and can be managed by removing affected foliage and improving air circulation.
Can you eat Welsh onion flowers?
Absolutely, the flowers are entirely edible and have a mild onion flavour with a slightly crunchy texture. I use them as an attractive garnish for salads, soups, and Asian dishes. They appear in early to midsummer as spherical clusters of small white to pale purple flowers. You can harvest individual florets or entire flower heads. Beyond culinary use, they’re excellent for pollinators, particularly bees, so I always leave some plants uncut to flower. The seeds that follow are also edible, though quite small and fiddly to harvest. Some gardeners collect them for resowing, but I find division much easier for propagation.
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Conclusion
Growing Welsh onions has genuinely changed how I approach allium cultivation in my garden. They’ve filled that perennial vegetable niche beautifully, providing reliable harvests without the annual effort of sowing and planting that regular onions demand. The fact that they’re hardy, relatively pest-free, and productive even in less-than-ideal conditions makes them suitable for gardeners at any skill level.
What I particularly value is their flexibility. You can harvest intensively when you need bulk for cooking, or take just a few leaves here and there for garnishing. They work in formal vegetable plots, cottage gardens, and containers with equal success. The initial establishment takes a bit of attention, but once they’re settled, they look after themselves with minimal input.
If you’ve not tried growing Welsh onions before, I’d encourage you to give them a go. Start with a small patch or even a single pot, and see how you get on. I suspect you’ll find, as I have, that they become one of those reliable staples that you wonder how you ever managed without.
Author: Megan Walker
Megan focuses on seasonal food, kitchen garden growing, and how households can reconnect with where their food comes from. Her writing blends practical growing advice with ideas for cooking and eating in season. With a passion for fresh ingredients and sustainable living, Megan’s articles help readers make the most of local produce while supporting British farms.