How to Grow Salad onions

Salad onions, also called spring onions and scallions, are easy to grow and take up little space, so can fit into even the smallest garden – and they grow well in containers too. Sow little and often for quick harvests, or make a larger sowing of a variety that has a long cropping season. Salad onions are delicious raw in salads or cooked in stir-fries.

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Salad onions are varieties of Allium cepa or Alliumfistulosum. There are many to choose from, either cylindrical like mini leeks or with small round white bulbs

These are fleshy, rounded, underground storage organs, usually sold and planted while dormant. Examples include daffodils, tulips, hyacinths, lilies, onions and garlic. The term is often used to cover other underground storage organs, including corms, tubers and rhizomes. topped with green leaves. For added decorative appeal, there are also varieties with reddish-purple bulbs and stems. Choose hardy varieties for early or late sowings.

For the most reliable varieties, look for those with an RHS Award of Garden Merit (AGM) – see our list of AGM fruit and veg (135kB pdf) – salad onions are listed under onions, and also our Recommended Varieties below. For more veg-growing inspiration, visit any of the RHS gardens, as they grow a wide range of onions, salad veg and other quick and easy crops.

What and where to buy

Seeds are available all year round from garden centres and online seed suppliers. Young plants may also be available to buy from garden centres and online retailers in spring and early summer – ideal if you only want a few.

Choose a sunny planting site, with free-draining soil, and weed thoroughly. Salad onions have a limited root system, so improving the soil with lots of organic matter before planting is invaluable – dig in a bucketful of homemade garden compost or well-rotted manure per square metre/yard. This will add nutrients, improve the soil structure and hold moisture in the soil. Avoid using fresh manure. Rake the ground to remove lumps and stones.

Alternatively, if you're practicing no-dig gardening, mulch

Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. the soil with organic matter ahead of sowing or planting directly into the mulch.

Salad onions are usually sown direct outdoors, either in the ground or in large containers. They can also be started off indoors, for an earlier crop.

Sowing indoors

It’s easiest to sow salad onions direct outdoors (see below) but, if your soil is cold and wet in early spring or you want an early crop, you can sow indoors in March. Sow the seeds in modular trays for transplanting outdoors later in spring, or sow in a greenhouse border or large container as their final growing site. See our indoor sowing guides below for more details.

Sowing outdoors

Sow salad onions outdoors from March onwards, for harvests through summer and into early autumn. Sowing small batches every couple of weeks will give you continuous supplies. You can also sow hardy varieties in late summer and early autumn for harvesting the following spring. These will germinate and grow into small, sturdy plants before winter and should be ready to harvest from March onwards.

Make a shallow drill

A miniature furrow typically 1–5cm deep, made with a stick, hoe or rake. It is used for planting seeds or bulbs, and ensures they are positioned at the correct depth and spacing. , 1cm (½in) deep, then water along the base. Sow the seeds thinly along the drill, then cover with soil. Space rows about 20cm (8in) apart. For more sowing tips, see our guides below.

Protect the seedlings

A seedling is a young plant grown from seed. from slugs and snails, especially in damp weather. Thin them out to about 2.5cm (1in) apart. Closer spacing may encourage downy mildew. The thinnings can be used in salads.

Sowing in containers

Salad onions grow well in a large pot at least 30cm (1ft) wide. Position it in a warm, sunny spot, close at hand for easy harvesting. Fill it with peat-free multi-purpose compost

Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. and water well. Then scatter the seeds thinly and cover with about 1cm (½in) of compost.

If you have sown salad onions indoors or bought young plants, plant them outdoors once they’re well rooted and growing strongly. Harden off young plants, especially if planting in early to mid-spring. Plant into prepared ground, spacing plants a few centimetres apart. Water the young salad onions before and after planting.

Salad onions are easy to look after and grow quickly. Keep them free from weeds and water them during prolonged dry spells.

Watering

Water young salad onions until they are well established, then only water during prolonged dry spells. Plants in containers need more frequent watering, as the compost

Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. can dry out quickly, especially in hot weather.

Weeding

Salad onions grow less well when competing with weeds for light and moisture, so weed regularly – hoe between the rows and hand weed between individual plants.

Winter protection

Hardy varieties of salad onion can be sown outdoors in autumn, for cropping in early spring. They often benefit from being covered with clochesor biodegradable fleeceduring winter, especially in harsh weather or in cold locations.

Salad onions generally take about two months to reach harvesting size. Simply lift individual onions whenever required. You can harvest from spring right through to autumn by making repeat sowings. Salad onions are best when small and young, about 15cm (6in) tall, with the bulb no more than 1–2.5cm (½–1in) across, depending on the variety. Young salad onions have a sweet, mild flavour, which becomes stronger as they grow larger.

Salad onions are fast growing and generally trouble free. Fungal diseases can arise in damp or overcrowded conditions. For more on these and other issues, see Common problems, below.