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Ease of Growing [Scale 1-5] - 2 (Easy/Medium)

How Time Consuming

Once the ground is prepared and the onion sets are planted, a weekly hoe through the crop will be required.  Regular watering in dry spells is required to prevent splitting, distorted growth or bolting (which means the crop has run to seed instead of putting growth into the bulb).

Recommended Varieties

From onion sets:

  • Stuttgarter Giant : suitable for all areas of the country, good taste, resistant to bolting and will keep well.
  • Sturon : Large white onion, does not bolt and will keep for long periods.
  • Rijnsburger : A very early round onion with resistance to bolting.
  • Red Baron :  This is a popular red onion, early to mature, bolt resistant and has a good colour.

Home Grown Vs Supermarket

A half kilo of onions sets will give you a good return.  As well as the ability to go out and pull a fresh onion or for storing after harvest for regular use.

Best Sites and Soils

Onions will grow well in an open sunny site in soil that is moisture retentive but has good drainage.  They will accept partial shade.  Onions have a limited root system therefore improving the soil with well rotted manure or organic garden compost is invaluable.  Onions do not thrive on acid soils below pH 6.5 so reduce the acidity by applying lime in autumn and winter.  They can be grown on the same site year after year although it is good to practice crop rotation by moving them on yearly to a different bed on a 4 yearly cycle.

When to sow

From seed as soon as the soil is workable, sow in spring for a late summer crop or in late summer for an early summer crop the following year.  Birds like to pull freshly planted sets from the soil, so it can be a good idea to cover the crop with fleece until the sets have rooted.  Alternatively, sow your sets into seed trays until they have rooted and then plant out into their final growing space.

When to plant

Plant sets from early to mid-spring.  
Distance between rows - 25cm (10”)
Distance between plants - 7.5-10cm (3-4”)

When to harvest

Mid to late summer when the leaves have turned yellow and start to fall over. Dig the onions uup and then leave them to dry out in the warm sunshine before storing in onion nets.

Meet the Author: Jo Blackwell
Jo Blackwell

Jo Blackwell is our well-established Horticultural Advisor and the Kitchen Gardener in Stephanie's Victorian style Kitchen Garden. She caught the gardening bug when she bought her first home 21 years ago. Her first greenhouse soon followed and she later gained an allotment.

As well as tending the Harrod Horticultural Gardens, she enjoys maintaining her own vegetable plot at home. She has been a gardener for Harrod Horticultural for over 4 years now and has a wealth of experience in organic vegetable growing, ornamental gardening and in using all Harrod products.


Further Information

Improving Soil

During the growing season apply a nitrogen rich organic fertiliser prior to any rainy spell.


Guide to sowing and planting - Push the sets into the soil the pointed end up with the tip just below the surface (to avoid the birds pulling them out).  
Onions are susceptible to weed competition so ensure regular weeding especially in the early growing stage.
Cover with fleece immediately after planning to prevent the birds stealing the sets.


Problems to look out for - White Rot – leaves will turn yellow and the plant will wilt. White fluffy mould will grow at the base of the plant.  
Rust – orange spots appear on the surface of the leaves which turn powdery.  Leaves may turn yellow and die.


How to harvest by type - Use a fork to loosen bulbs from the soil and leave to dry out in the sun until the skins are crispy.

Storing - Knock off soil when dry and store in nets in a well ventilated frost-free place or tie them and hang them up ready for use.

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