Onions are a biennial crop, producing foliage in their first season and over-wintering as a bulb before flowering in their second year.

Commercial onion sets are immature bulbs that have been specially grown for planting.

There are several advantages in using sets rather than seed. They are quick maturing, succeed in northern areas where seed crops may disappoint and they are not attacked by onion fly or mildew.

Less skill and less soil fertility are required, but against these advantages must be set the extra cost and the extra risk of running to seed (bolting). To avoid this it is best to buy sets that are no larger than 2cm across. Onions only become sensitive to cold at a certain size, so manipulation of sowing and planting dates lessens bolting.

Commercial shallots are already full-sized  when planted in early spring they quickly start to grow and eventually produce a cluster of 8 to 12 similar-sized bulbs in summer.


All onions require good soil and free drainage, which should be neutral to alkaline. Dig over well in advance, but do not apply manure just before planting, as this can result in soft, disease-prone growth. Sets need neither the fine texture nor the high organic content demanded by seed-grown onions.

Dig in early winter and incorporate compost if available. Lime if necessary. Firm the surface before planting and rake in a general fertilizer such as Growmore.


If planting is delayed, open the package and spread out the sets in a cool well-lit place to prevent premature sprouting. Plant onion sets 10cm apart in mid March – mid April. Shallots require wider (15cm) spacing and earlier planting (mid February mid March).


Protect from birds with black thread or netting if they are a nuisance in your area.

Keep weed free by hoeing and hand pulling.  Push back any sets which have been lifted by frost or birds. Once the sets are established and shoots have appeared then break off any flower stems which appear. Mulching is useful for cutting down the need for water and for suppressing weeds. Stop watering once the onions have swollen and pull back the covering earth or mulch to expose the bulb surface to the sun.



The bulb is mature when the foliage turns yellow and topples over. Leave them for about 2 weeks and then lift on a dry day. Spread the onions on trays and dry for 7-21 days depending on the size of the bulbs and the air temperature. Inspect the bulbs carefully – all soft, spotted and thick-necked onions should be set aside for kitchen use or freezing. The rest can be stored.


In July the leaves will turn yellow. Lift the bulb clusters and separate them, allowing each shallot to dry thoroughly. Remove dirt and brittle stems, and store in net bags in a cool, dry place. They will keep for up to 8 months.


Giant: a flat shaped, yellow skinned set with a good yield and keeping qualities. Plant early.Sturon:
A rounded onion which stores well with high yields. Mid-season

Ailsa Craig:
round, large and straw-coloured.  Mild-flavoured flesh.

very high yield, with excellent keeping qualities.


One of the earliest red shallots and resistant to bolting.

Red shallot with a mild flavour.

Golden Gourmet:  
Yellow shallot which can be planted very early.  Mild flavour and good for pickling.  Good yield and keeping qualities.


Garlic can only be propagated vegetatively from sets and will not set viable seed. For this reason garlic cloves should be purchased and planted.

In the UK a single clove should be planted in spring in a warm section of the veg plot.

In the first season these cloves will grow into a single round which should be lifted and overwintered, then replanted the following spring.

At the end of the second season the round will have developed into a large, multi-cloved bulb.

This is the point at which the cloves should be split. One half can be used, the other can be replanted so another year can be gained.

It is worth buying new cloves for planting after 2-3 years so that the crop is started with a strong young clove.


From the same family (Allium) the leek is another onion-like crop that can be grown happily from seed or young plant.

Seed can be planted indoors at a gentle heat of 7°C, and planted out in March.

When the leeks reach 20cm they can be planted out their final position anytime from June to August.

Any extra feed you can apply at the time of planting will help greatly with establishment and growing on.

Leeks are traditionally planted at the bottom of a 15cm hole and soiled up to increase the ‘blanched’ area on the leek. This can also be achieved using a collar to prevent the light getting to the stems.

Leeks should be planted 15-30cm apart. A wider spacing encourages bigger leeks.

Plants can be affected by rust. This manifests itself in bright orange spots. Control is possible but it is usually better to remove infected plants and burn them.

Eelworm can be a problem in leeks but there is nothing that can be applied on the domestic market that will successfully fix the problem. Again, the best solution is to remove the crop and burn it.

Do not compost anything that has been infected. Where possible, particularly in the case of Eelworm, try to move the crop to a different part of the plot the following season. 

There are many different varieties of leek and the varieties available as young plants can vary from year to year. If growing from seed you can select from a broad range of plants – from short and stout, to slender and tall.


Spring onions are a quick salad crop that don’t require as much time or attention as other bulb onions. Light, well-drained soil is perfect and the density of planting should be around 30cm apart.

Seed is usually sown as a summer crop between March and June.