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Growing Giant Onions in AutoPot Watering System

Some of the best reactions I get when visitors come to look around the greenhouse displays are when they turn a corner and their eyes suddenly fix on to the giant onions. “Wow!…Look at those onions!” they cry in astonishment and every time it brings a big smile to my face to see their amazement and wonder at these massive alliums. I have grown these impressive exhibition onions for a few consecutive seasons now, mostly for fun and the wow factor they give to the greenhouse displays, but also with one eye on beating the previous season’s top weight.

Writing this and thinking back to when I first had a go at growing giant onions in 1996, I realise that it has been 20 years. My first attempt back then was using an NFT channel system I had on display – I grew big onions but nothing like the ones I get now. Saying that, I think the current record holder for the heaviest onion (15lb 5oz I believe! That’s about 7kg), won’t be worried about losing his title to me….just yet.

If you are planning on taking that record for yourself, or you want to beat my top weight, or just to grow something to impress your friends and family with, then you need to start with the right seed varieties.  The two main varieties of choice for the exhibition grower in terms of size and weight are Mammoth, which holds the current record, and Kelsae.  You can get both varieties in seed form and can sometimes be found as ‘sets’ (a small bulb that grows in to a full sized single onion), and as young live plants ready to plant out.  Like many growers I like to start my onions from seed, I’ve heard that it’s preferred by the pros for the best chance of a whopper – I like the satisfaction of starting with something so small, such as a seed, and seeing it end up as a huge onion.  The best seeds, if you are lucky enough, are directly from a giant onion grower who has produced seeds from his monster sized prize winner.

I managed to beat my personal best with an onion of 2.67kg this year with the Kelsae variety, I did grow a batch of the same onions using Biobizz organic medium and feeds as well as compost tea.  Not quite as big but that’s what I was expecting. You can see both results below.


If you are not man enough to eat a whole giant onion in one sitting (what’s wrong with you?) then chop it all up and freeze it.  You can then use just the amount you need straight from the freezer directly in to the pan – easy-peasy…er…oniony!?!
Have fun growing your own onions from seed and I would love to hear your experiences good and bad, funny or not. Or just drop us a message to brag about how good your onions are and we will give them the recognition they deserve.

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