Use sets instead of seed for onions

‘With sets you’ll get a perfect stand regardless of the weather and be able to harvest earlier.’

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There is a safer but more expensive way to get onions to mature in autumn, when prices are at their highest. This is by planting sets.  Sets are basically picklesized onions, which can be transplanted instead of direct seeding.

This removes many of the climatic hazards when seeding at peak temperatures in a rainy period. It’s especially useful for cooler, wetter, short day areas.

Using sets
Not all onion varieties are suitable for making sets. Get advice from a reliable seed representative. Generally, but not always, a slightly flatter onion variety is a safer bet than a round one.

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Maturing into this time of the year, onions tend to become deeper in shape, and some round varieties will tend to make more elongated bulbs, often called “torpedoes”.

These longer onions have a much shorter shelf life as they tend to want to start growing new leaves. Having chosen an appropriate variety, you now must make seedbeds.

Sow the seeds at seedbed density from July to early September, preferably in July/August. As seedbeds are a manageable size, you can protect them with frost blankets or netting. You’ll get good value from the seed as you can provide perfect conditions at a time of year that poses few hazards.

Keep the seedbeds growing steadily. Forcing them with too much nitrogen will cause unevenness as certain plants will dominate and shade out their neighbours, so that some sets become too large and others stay too small.

A medium, healthy colour will do – not too dark. By early December, the longer days will be a factor and the onions will start to bulb. At this stage it’s better to have medium-light leaves. Start reducing irrigation to stress the plants.

This speeds up bulb formation and causes leaves to die back. If the beds have been protected with netting or frost cover using wire hoops, put clear plastic strips in-between the beds.

These can be pulled over them to induce water stress in a rainy period. Just make sure the covers aren’t left on during bright sunlight or the plants will burn. When the bulbs have formed and the leaves have dried off, lift and store the onions until February/March when they’re transplanted.

Store them in a dry area on straw or even hang them in netted bags so that there’s some air movement. Transplant either by hand or machine.

Orient the sets right-side-up when hand planting, though this method is out of favour since government legislation encouraged farmers to shed labour.

With sets you’ll get a perfect stand regardless of the weather, and should be able to harvest earlier, sometimes even in May. With all the stored reserves in the bulb, the plant gets a rapid start compared to seed.

However, there are disadvantages to sets. You’ll tend to get more split bulbs, causing a downgrade on the market. Your costs can also be higher because you are producing two growth phases for one crop, transplanting and storing the sets for a few months.

You may also have to grade the sets into similar sizes if there’s a lot of variation.

Making pickles
Pickles are produced the same way as sets and bed density determines the size of the onions.

Space cocktail onions much closer. White onions are favoured for pickling as they’re more attractive in bottles.

Some small pickle producers buy cheap undersize onions on the market but the quality and appearance are inferior.

Large producers are well-mechanised, produce firm, white bulbs and even use a gas flame to burn off the dry tops before lifting to cut labour costs.

Contact Bill Kerr on 016 366 0616 or email [email protected]

Don’t mix small and large sets as the larger ones will sprout later, as seen here.


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