Your Welsh onions have arrived: an autumn planting guide

Our Welsh onions are looking strong and will start heading out in the week beginning 26 October. They have spent the last couple of weeks hardening off outdoors, through cold nights and strong winds, so they are already used to autumn weather.

If you have ordered some, here is how to help them settle into your garden this autumn and get ready for next year's harvests.

When your Welsh onions arrive

Unpack them promptly and check the compost. If the plugs feel dry, give them a gentle watering and allow any excess water to drain away. Keep them somewhere bright and sheltered outdoors until you are ready to plant.

They have already been hardened off, so there is no need to bring them into a heated house. Plant them as soon as conditions are suitable, or pot them on if planting needs to wait.

Can I plant them out in late October or November?

Yes, provided the soil is well drained, workable and neither frozen nor waterlogged. Choose a sunny spot with some shelter from strong winds. Welsh onions are perennial, so give them a home where they can stay and develop into larger clumps over the coming years.

If your garden has heavy soil that stays wet through winter, a well-drained raised bed or a pot with drainage holes may be a better choice. We’re using a raised bed with some sand and grit mixed in to the top few inches of the soil for better drainage. In very cold or exposed areas, you can also pot the plugs on and overwinter them in an unheated greenhouse or cold frame, then plant out in spring if you prefer.

Should I separate the onions or plant them in clumps?

I have usually separated mine into individual plants, and each one can gradually grow into its own clump. You can also plant them in small groups.

For autumn planting, it may be best to leave each small plug clump together to keep root disturbance to a minimum. You can divide established clumps later if you want to spread them out.

1. Clear the planting area of weeds.
2. Space small plug clumps around 20-30cm apart to give them room to grow. If you decide to plant them individually 10cm should be enough space. 
3. Plant with the top of the plug about 1–2cm below the soil surface, keeping the green leaves above ground
4. Firm gently around the roots and water in to settle the soil.

A little mulch and winter protection

A mulch of well-rotted garden compost around the plants isn’t essential but it can help suppress weeds and protect the soil. Aim for roughly 4-5cm over the surrounding bed, but leave a clear gap around the bases of your onions. Keep the leaves and growing points uncovered.

While the plants are settling in, a temporary cover of horticultural fleece or a ventilated cloche can help during hard frosts or particularly harsh weather. Secure it against the wind and remove or open it when conditions ease. Protection offers a little extra help; good drainage is still essential.

Check occasionally that the roots have not dried out, especially in pots or under cover. Keep the compost lightly moist rather than soggy, and never leave pots standing in water. 

What should I expect over winter?

Growth will slow as the weather cools and the days shorten. Some leaves may yellow or die back during cold spells; this does not necessarily mean the plant has died. Look for fresh growth when conditions improve.

For these autumn-planted plugs, I recommend letting them establish over winter before taking a harvest. Once they are growing strongly in spring, you can begin snipping a few outer leaves, leaving plenty to keep the clump growing.

Welsh onions offer that lovely fresh onion flavour in salads, soups, omelettes and stir-fries. With a suitable spot and a little care while they establish, a small planting can become a useful part of your kitchen garden for years.

View our Welsh onion plug plants