How to Grow Spring Onions: A Practical Guide from Seed to Harvest

Spring onions are one of the easiest vegetables to grow from seed and they're particularly useful if you only have a small amount of space. You don't need a vegetable bed — a pot, trough or window box can give you a perfectly good crop.

White Lisbon is the classic variety and a very reliable place to start. It produces crisp white stems with fresh green tops and has that mild onion flavour that's useful in salads, sandwiches and stir-fries. There are many other great varieties to try.

The trick with spring onions is much the same as radishes and rocket: don't sow the whole packet at once. I prefer a small sowing every few weeks so there are always younger plants coming along behind the ones we're harvesting.

They grow quickly, don't need much attention and you can pull them as soon as they're large enough to be useful.

When to Sow 

Spring onions can be sown directly outside from March to August.

I usually start sowing once the soil begins to warm in spring and then make another small sowing every few weeks.

There's really no advantage in having hundreds ready at once. A short row or small patch in a container is usually enough, particularly if you're sowing for the kitchen rather than trying to produce a huge crop.

Later sowings during summer will keep fresh spring onions coming into autumn.

If you're growing in containers, it's very easy to succession sow. Once one batch has been harvested, refresh the surface of the compost and sow again.

How to Sow

Spring onions are best sown directly where they're going to grow.

Prepare the soil and make a shallow drill around 1cm deep.

Sow the seeds thinly, cover lightly with soil and water gently.

Keep the soil reasonably moist while the seeds germinate. In good conditions, seedlings will usually begin appearing within a couple of weeks.

For containers, fill a pot or trough with multipurpose compost and sow in exactly the same way.

You don't need to give every seed an enormous amount of room. Spring onions are harvested while they're still relatively small and can be grown closer together than full-sized onions.

Thinning and Growing On

Spring onions need very little attention once they're growing.

Thin badly overcrowded seedlings so the stems have enough room to develop. You can do this gradually rather than trying to achieve perfect spacing immediately.

And don't automatically throw the thinning's away. Once they're large enough, the young plants can be eaten.

Keep weeds under control while the seedlings are small and water during dry weather.

There's no need to transplant them, stake them or spend weeks potting them on.

That's one of the reasons I like them for beginners and smaller gardens. Most of the work consists of sowing, watering and eventually pulling them up.

Growing Spring Onions in Pots

Spring onions are excellent for containers.

They don't need a particularly deep or enormous pot, so they're useful when patio space is limited. A trough or window box can work just as well as a conventional plant pot.

Make sure the container has drainage holes and fill it with good-quality multipurpose compost.

Sow directly into the container and keep the compost reasonably moist.

You can grow quite a few spring onions in a relatively small area, which makes them much more useful for a tiny garden than some vegetables that need an enormous pot for a single plant.

I like the idea of having two containers at different stages. While you're harvesting one, the next sowing is already coming along.

Watering and Feeding

Spring onions grow best when they have reasonably consistent moisture.

They don't need permanently wet soil, but try not to let young plants repeatedly dry out during warm weather.

Container-grown crops need checking more frequently because pots can dry surprisingly quickly.

Water thoroughly when necessary rather than continually giving the surface a little splash.

In reasonable garden soil or fresh multipurpose compost, spring onions generally don't need much additional feeding.

They're a relatively quick crop and we're harvesting them young.

If you're repeatedly reusing the same container, refreshing some of the compost between crops is often more useful than continually adding fertiliser.

Harvesting

Spring onions don't have a complicated definition of when they're ready.

Once the stems have reached a useful size, start pulling them.

You can harvest the largest first and leave smaller plants to develop for a little longer.

I prefer them young, while the stems are crisp and the flavour is still relatively mild.

Loosen the soil slightly if necessary and gently pull the whole plant.

Both the white stem and green leaves can be used, so very little needs to be wasted.

And don't feel you have to wait until every plant looks exactly like the spring onions in a supermarket packet. You're growing them for yourself — if they're large enough for tonight's salad, they're ready.

Succession Sowing

Succession sowing is probably the most useful thing you can do with spring onions.

Make a small sowing every few weeks rather than one enormous sowing in spring.

That spreads the harvest and gives you younger plants coming along throughout the season.

It works particularly well in containers because the same small area can be used repeatedly.

Spring onions also fit neatly between slower-growing vegetables while those crops are still small.

For a patio or small garden, that's important. The trick isn't necessarily cramming more plants into the space at one time — it's keeping the space productive throughout the season.

Common Problems

Poor Germination

Spring onions normally germinate reliably, but cold, waterlogged soil can slow early sowings.

Very dry compost can cause problems later in the season too. Keep freshly sown soil reasonably moist until the seedlings appear.

Overcrowded Seedlings

If plants are packed tightly together, the stems may remain thin.

Thin them gradually to give the stronger plants a little more room. Use edible thinnings rather than wasting them.

Yellowing Leaves

A few older yellow leaves aren't usually anything to worry about.

More widespread yellowing can be caused by waterlogged soil, very dry conditions or exhausted container compost.

Check the growing conditions before automatically adding feed.

Onion Fly

Onion fly can occasionally affect members of the onion family, with larvae damaging the roots and causing plants to wilt.

Crop rotation and keeping the growing area clear of old onion-family debris can help reduce problems.

Slugs and Snails

Young seedlings can occasionally be damaged during damp weather.

Keep an eye on new growth until the plants are established.

Plants Growing Slowly

Cold weather can slow spring onions considerably.

If an early sowing seems to be sitting there doing very little, give it time. Once temperatures improve, growth usually picks up.

Spring onions are exactly the sort of crop I like for a small growing space. Sow a few, keep them watered and pull them young. Then sow some more. White Lisbon is a particularly good place to start — reliable, straightforward and perfectly happy growing in a container when you don't have room for a vegetable garden.