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Why I Grow Onions from Seed

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I like to grow my onions from seed, which seems to be uncommon here in the UK, where most people will use sets. Unlike using onion sets, which are small, dormant bulbs, starting onions from seeds opens up a wider variety of options since there are more seed varieties available than sets.

This variety lets me experiment with different flavours and sizes, tailoring my vegetable patch to my culinary preferences and kitchen needs.

Growing from seed is also much more cost-effective, as seeds are substantially cheaper than sets, and each packet contains many seeds, which means I can grow a plentiful supply of onions for a fraction of the price.

Then comes the big reason for me: onions grown from seed are much less likely to bolt than those grown from sets. I will get into this in more detail later on.

Onion Seeds
Onion Seeds

Benefits of Growing Onions from Seed

More Variety

This one is simple enough: if you grow from seed, there are many, many more varieties of onion that you can grow and experiment with when compared to sets.

Just take a look at all the different varieties available at my favourite seed store, Premier Seeds Direct.


Another one that is self-explanatory, seeds will always be cheaper than sets. Whereas a set has to be grown, harvested, and cold stored, seeds simply have to be harvested and packed.

You can get hundreds of seeds in a pack for just over a quid. And onion seeds are good germinators, too, so a lot of them will end up as viable plants.

Less Likely To Bolt

This one does require a little more explanation, but once you understand the life cycle of an onion, it becomes clear.

Onions are biennials, meaning they have a life cycle of two years. They will grow and bulb in the first year before flowering and setting seed in the second year.

As we grow onions for the bulb, we only treat them as annuals, so they should never flower (unless this is intentional for seed harvesting).

But they do flower; when this happens early, this is known as bolting, and it ruins the crop. This usually happens when the plant is stressed – often because of a hot, dry spring.

This is much more likely to happen with onion sets as the plant has already been grown, then halted and stored before being planted again. This can lead to confusion where the plant is more likely to act like it is already in its second year of growth.

Cold storage is one-way growers of onion sets combat this, but it is never as effective as just simply growing them from seed. If bolting is a problem for you, I highly recommend you try growing from seed!

How To Sow Onion Seeds

You can sow onion seeds very early in the season, with some people sowing them as early as December. I often start mine from January onwards.

Simply sow the seeds in a module tray, you can sow anywhere from 1 – 10 seeds per module, they really aren’t too fussy.

Onion Seeds In Module Trays
Onion Seeds In Module Trays

If sowing early in the year then you may need to sow indoors or provide extra protection such as a propagator or fleece.

Once your seeds are established you can plant them out into the garden. You can leave them as a cluster and plant them out all together or separate and plant them singularly.

If you plant in a clump you will get smaller onions but more in total. You can also adopt a hybrid method where you plant them as a clump but harvest some of the onions young as spring onions, before allowing the others to grow on into larger bulbs.

So that’s why I grow my onions from seeds, I have a full sowing guide with step-by-step images coming soon, so keep your eyes peeled for that. And if you have any questions then feel free to pop them in the comments below!


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