RHS Growing Guides
How to grow salad onions
Our detailed growing guide will help you with each step in successfully growing Salad onions.
Getting Started
Sow little and often for a supply of salad onions from spring through to autumn
Month by Month
| J | F | M | A | M | J | J | A | S | O | N | D | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sow | ||||||||||||
| Plant | ||||||||||||
| Harvest |
Choosing
Different varieties can have white or purple stems, and all are quick and easy to grow
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.
Recommended Varieties
Straight, elongated, white stems. Good yields over a long harvest period, from June to October.
Preparing the Ground
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 the soil with organic matter ahead of sowing or planting directly into the mulch.
Sowing
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, 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.
Sowing in containers
Sowing times can be extended by growing salad onions in a container in a greenhouse
Planting
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.
Plant Care
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 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
Harvesting
Slice young salad onions finely, to add a mild tangy flavour to salads
Problems
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.
Get involved
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