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.
You should sow your giant onion seeds between mid-December and mid-January for a harvest at the end of July to mid-August. Fill a clean cell tray or small pots with a free draining compost medium. Choose a good quality seedling compost mix, 50/50 multi-purpose compost & coco fibre or perlite mix. Alternatively you can choose to use a plug type product like Root Riot, Jiffey 7s or Grodan rockwool. Fill the cell tray or pots and settle by banging onto the work surface a couple of times, then stand them in a tray of water to soak before planting the seeds. Leave to soak for about an hour or until the medium is well saturated. Remove from water and allow any excess water to drain briefly. With a small dibber or flat end of a pencil (the rubber is perfect) make a small indentation approx. 2-3mm deep in the center of each cell or pot. Place one seed in to each indentation and cover with a thin layer of fine grade vermiculite – covering the seed and surface of the cell or pot thinly. Now mist the vermiculite with water using a hand sprayer with a fine mist to wet it well. Now place the tray or pots into a propagator with a lid on and vents closed and place somewhere warm. Germination temperatures should be kept stable between 24-28 degrees C (75-82F). No light is required until the first signs of germination, but at the first sign of the first shoot, light will need to be applied from thereon. A T5 fluorescent propagation light or LED propagation unit is usually the preferred choice for seeds and cuttings. In past seasons I have given the seedlings 24 hours of light from the first day of sprouting until moving into the greenhouse in April where artificial lighting is only used for a couple of hours at the end of the day. Next year I am going to try lighting some of them for only 16 hours of light per day and compare them to the ones on 24 hours continuously. I have read that someone was getting better end results by adopting this method at the start, so I’m going to be giving it a try. Germination usually takes 7-14 days with a high germination rate. I regularly get 90-100% germination so you only need to sow a few extra than required, 10% is plenty. After germination open the propagator vents, place under artificial lights and reduce the temperature to around 18 degrees C removing the propagator lid completely after 7-10 days. If the cell tray or pots need watering at any stage, simply stand them in shallow water for 30mins then remove.