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How to Grow a Giant Onion

Here's Peter Glazebrook (2012) with the World's largest Onion weighing 8.195kg/18.06ozs



Here are some growing tips from the World's best grower of Onions - Peter Glazebrook


Peter Glazebrook from Notts in 2012 has grown the worlds heaviest onion weighing just over 18lbs

Peter's onions are selected each year and onions are seeded down and these are open pollinated.  The seed is taken from largest onions of the same strain. They have the potential to grow large but need the right method/conditions.

Top Tip

Give a long growing season. This is only possible with lighting/heating (or at least prior to planting out)


If sown in November they would need adequate lighting right through the winter, grown in a heated greenhouse with a minimum of 8c


Planting out

They are best grown if planted out late winter/early spring under protection in full sun and grown on until harvest in late summer.


Onion in pot

A structure which can be fully ventilated in the hot weather such as a polythene tunnel or large greenhouse is best.
Unless your proposed soil is clean and of a high quality, it may be better to plant into raised beds or very large pots filled with sterilised soil/compost.  Regular careful watering is better than making them over wet, never water overhead.  Control insect pests etc, as you will do for any vegetable.


Onions in heated tunnel

Peter has been been able to plant out at the end of February mainly because he has a double insulated tunnel allows him to warm up the growing area and then keep it warm.  (The onion plants require a minimum soil temp of 55f (12c) + adequate lighting during the dark winter days.)

Many onion growers wait to sow after December 21st on the basis that the days will start to lengthen after germination, with a heated greenhouse and suitable protection for growing on through the summer 8lb is quite possible, even more if the onions were to be started with around 6 weeks of 24hr artificial lighting.

Watering and Feeding

Always try to water in the morning on sunny days, but keep them on the dry side if cool and grey.  Peter always uses tepid water from the kitchen mains supply.
Feeding is not recommended as it is better to rely on good quality composts and regular potting on into larger pots. Professional Soil test is essential for the growing area, ensuring that he adds the recommended fertilisers before planting and no more.

Peter believes that concentrating on a few rather than many is his secret to success

Many amateur large onion growers in the UK are using Peter's seed and seem happy with their results, however not everyone has the same experience or goes to the same time and trouble as Peter, hence him being the undisputed King of Onion growing.


Click here to purchase Peter's onion seeds


onion towards end of season