Land of the Giants – growing big onions

Last year, almost by accident, I grew a large pumpkin. Well there were five big ones but two BIG ones. I say by accident because I planted the three ‘Atlantic Giant’ plants with the other squash, including butternuts and ‘Crown Prince’ in well-prepared soil in front of sweet corn and dahlias, amaranth and quinoa. They had no special treatment and I was pleased to see that two started to get to a big size with no special treatment. Now these were not record beaters and they were runts compared to what the variety can achieve, but both tipped the scales at more than 40kg so they were not bad really.

Ashamed of its small size, this 40kg pumpkin is hiding in the foliage

Ashamed of its small size, this 40kg pumpkin is hiding in the foliage

This has inspired me to grow a few more big veg (I know a pumpkin is a fruit) so I have bought some from my good friends at Robinsons seeds, home of the Mammoth onion.

Susan and Margaret have kept the business going and maintaining their unique range of wonderful varieties – and not just all big’uns. Their ‘Britain’s Breakfast’ tomatoes are quite something and they offer some really unusual veg and a good range of squashes.

Anyway, I am dabbling with cabbages and leeks but it is the onions that are my focus today.

An early start

To grow a big onion you need to start early. This is because onions stop making new leaves after the longest day. Now since an onion bulb is made up of the base of the leaves – each ring is a leaf base – if you want a big onion, made of a lot of rings, you need it to make lots of growth before June 21st. After that the onion bulb may still grow but no more leaves will be produced. That is why it is traditional to sow giant onions as soon after the shortest day as possible and it is common for the seeds to be sown on Boxing Day or New Year’ day. I opted for the latter.

To give your onions the best chance of growing big you need to give them the best of everything. The seeds of giant veg have the ‘potential’ to get big but if they are starved or sown late they will not reach their potential. The seeds were sown in a mix of multipurpose and John Innes – Robinsons recommend John Innes but the stuff I had was so wet and sticky that I wouldn’t sow weeds in it. It is recommended that the seeds have gentle heat and are not exposed to high temperatures so I kept them in the heated part of the greenhouse, kept at a minimum of 10c. Germination was slow but by yesterday they were large enough to transplant.

Onion seedlings ready to transplant

Onion seedlings ready to transplant

It is best to transplant them when they are at the ‘crook’ stage, before the first leaf has become fully upright. At this stage their single root is small enough to get back into a pot without breaking. Lift the seedlings by pushing a dibber (I always use a label) under the seedlings and then carefully lift the seedling out by gently holding the green leaf. Do not tug them.

Handle the seedlings carefully so you do not damage the one root. Unlike most roots, bulb roots do not branch if they are damaged - new ones are produced from the base of the bulb.

Handle the seedlings carefully so you do not damage the one root. Unlike most roots, bulb roots do not branch if they are damaged – new ones are produced from the base of the bulb.

Make a hole in the new compost and carefully work the root into the hole so the seedling is at the same depth and firm the compost – I put the dibber into the compost beside the seedling and gently push sideways – watering will do the rest of the firming. I transplanted my seedlings into cell trays. I use six and twelve-cell trays (half tray size) for all my seedlings. I used the same mix of multipurpose with John Innes and I tend to add a little Perlite to taste!

One onion seedling is carefully moved to its new home

One onion seedling is carefully moved to its new home

What is needed now, apart from some sun, is to keep the plants growing steadily and without any check to growth. So as soon as the seedlings fill their cells with roots they will be potted into larger, individual pots. My plan is to grow some in the greenhouse but most outside. So far I have more than 100 to play with so we will see how they get on – stay tuned.

By the way, there is still time to sow some seeds for big onions. The Mammoth strain I am growing is capable of producing bulbs 3kg in weight. I will be happy with 2kg. If you sow in the next few weeks there is not reason why you can’t produce 1kg onions and that is pretty impressive.

PS The big pumpkins were used locally – Springmount Garden Centre – –   to raise money for the local school and amuse drinkers at the Tara Vie – . We will see if I can do the same with the onions and leeks.

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One Comment on “Land of the Giants – growing big onions”

  1. joy
    February 6, 2014 at 8:52 pm #

    very enjoyable and look forward to seeing those huge onions

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