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Dublin: 10 °C Thursday 2 April, 2020

GIY: Our guru's 'nerdy' guide to growing onions for home-made marmalade

This onion marmalade recipe is a sinch to make so if by chance you still have a glut of onions from last year, writes Michael Kelly.

Michael Kelly Grower

WITH THE TRANSITION into April, I am starting to think about sowing onions here at home. Onions are a sinch to sow – we use what are called ‘sets’, which are basically immature onions.

You can grow onions from seed as well but I have to confess that I never bother. Sets have a headstart over seeds, so they have a better chance of maturing.

I am keeping a wary eye on the cold weather before committing. A GIY friend told me once that if you could sit your bare bum down on the soil then it’s warm enough to sow your onions. I think that says a lot about the kind of weird stuff he gets up to in his garden.

I’m geeky when it comes to sowing onions

Anyway, there’s a grain of truth in it. You should sow your onion sets between mid March and mid April (to sow from seed you need to start them in February), but it’s best to wait until the soil has warmed up a little.

If you do want to go ahead with them, a fleece cover over them will keep them a little warmer and has the added benefit of keeping the birds away (crows and pigeons are inclined to pick at the sets). You will need to remove the cover once the sets start to grow.

I get seriously geeky when it comes to sowing onions – I have a 5m bed to sow them in and I get 4 rows in the bed. The onions are sown at 10cm spacing in the rows which means I get 200 onions from the bed. I run a line of twine along to mark out the row and then space the onions at 10cm.

Spacing is important

There are a number of reasons for being so nerdy about this – first of all, it just looks so damn pretty when they start to grow. Secondly, the spacing is important. 10cm gives you the perfect (in my opinion), medium-sized onion – you could go to 15cm and get giant onions or pull back to 7cm for smaller ones. Finally, having an ordered grid like this makes it easier to run the hoe between the rows to keep on top of weeds.

To sow the sets you simply push it in to well-prepared soil so that that the tip is just showing above the surface. Try and find nice round sets, avoiding the oblong, tapered ones which are more inclined to bolt. If birds pick the sets out on you, dig them up and plant them again carefully – don’t push them back in as you might damage the roots.

Yesterday I was hoeing in between the over-wintered onion sets here at home. These were sown before Christmas and should be ready a little earlier.

Richard, our Head Grower at GROW HQ thinks that over-wintered onions are very likely to bolt (run to seed) this year because of the snow last month. He intends to harvest the ones at HQ as scallions just in case. Check out the GIY video tutorial on growing onions here.

The Basics – Sowing Direct or Transplanting?

We are often asked in GIY whether it is better to sow direct into the soil or in pots and trays (for planting out later). It’s always a tough question to answer because it depends on the vegetable and there are also other variables. Sowing direct is far less time consuming, but there are risks involved (tiny seedlings being eaten by slugs etc).

Root crops such as carrots and parsnips are better sown direct, because they don’t transplant so well. Vegetables with large seeds such as peas and beans are generally sown direct – you can sow in pots earlier in the season if it’s too cold to sow outside directly. Onions, garlic and potatoes are all best sown direct.

I think that most other vegetables are better sown in modular or cell trays. The seedlings can then be transplanted into the prepared bed or potted on into bigger pots. This has the added advantage that those well established small plants are more resistant to slug attacks.

You can buy different types of plastic or polystyrene trays or you can recycle yoghurt pots and cut milk cartoons for use as home-made seed trays.

Recipe of the Week – Onion Marmalade

This onion marmalade recipe is a sinch to make so if by chance you still have a glut of onions from last year, then this is a nice one to try.  It makes a great accompaniment to all kinds of meats.


  • 1kg onions
  • 5 tablespoons red wine vinegar
  • 100g brown sugar
  • 2 tablespoons oil


Peel and chop the onions and fry them gently in the oil until they are soft. Increase the heat and add the red wine vinegar and the sugar.

Cook, stirring continuously, until it turns sticky.

Michael Kelly is founder of GIY and GROW HQ. The GIY TV series GROW COOK EAT is on Wednesdays on RTE 1, presented by Michael Kelly and Karen O’Donohoe.

Click here for more GIY tips and recipes.


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Michael Kelly  / Grower

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