Growing onions from sets

[veggiemad]

Hi all,

I'm fairly new to this and planted some onion sets around 2-3 weeks ago. Most of them are coming up which is great.

One question I have is, how do onions grow from sets? Does the bulb you plant just get bigger and as a result produce 1 onion. I know it's a silly question but I'm a bit confused and keen to know how it works. If anyone could explain this mystery that would be great.

Thanks!

[chris]

Yes, the bulb swells up to produce 1 onion. Think of it as an immature onion, which most likely has been heat treated to destroy the seed embryo inside it, so it shouldn't bolt (produce a flower to set seed).

[veggiemad]

Thanks for explaining Chris - best get out there and plant more sets then! ) Hopefully I'm not too late.

[Bigmallly]

Unless it's a shallot which splits and produces several bulbs.

[rpt]

If you grow shallots from seed you only get one bulb per seed. So if you plant one of these bulbs, will that work like a set and give you several bulbs?

[veggiechicken]

Veggiemad
When you cut an onion in half you see lots of rings. Imagine the small set that you plant, growing extra rings around itself to become larger. If you leave an old onion it will sometimes throw a green shoot, if that onion went into the ground again it could grow even larger. Not recommended though as usually they're going soft by then and might rot.
rpt
I don't grow shallots from seed, only from sets, then save some of those to replant for the next year's crop. I think that a shallot from seed would produce one set, and you could replant that and it would multiply for the following year.
However, there are exceptions, like Banana Shallots that have to be grown from seed and produce an edible set the same year - more info elsewhere on the Forum.

[Bigmallly]

Just to echo vc's comments, banana shallots can only be grown from seed & produce one bulb.

[veggiemad]

Oh right - I've planted some banana shallots sets - so does that mean that they won't grow?

I'll get the hang of this one day!!

[Aberdeenplotter]

Yes, the bulb swells up to produce 1 onion. Think of it as an immature onion, which most likely has been heat treated to destroy the seed embryo inside it, so it shouldn't bolt (produce a flower to set seed).

Chris is correct with what he says except about being heat treated. Onion sets that are not labled as being heat treated will not be heat treated. They cost more, are normally only available direct from seed companies and are normally available later than non heat treated.

[Aberdeenplotter]

Veggiemad
If you leave an old onion it will sometimes throw a green shoot, if that onion went into the ground again it could grow even larger. Not recommended though as usually they're going soft by then and might rot.

VC tsk. Onions are bi-ennial and an onion grown to maturity in year one will seed in year two. They will not grow any bigger, in fact the flesh of the onion may well shrink/rot away

[veggiechicken]

I hang my head in shame Oh Mighty onion grower! My excuse is that I am rubbish at growing onions and sometimes the onions that emerge at the end of the year are little bigger than the sets I started with! You will, I hope, have noticed all my wriggle out caveats like " Could grow larger" and "Not recommended" "going soft" and "rot".

[Aberdeenplotter]

sometimes the onions that emerge at the end of the year are little bigger than the sets I started with!

. Okies, in that case, I will unreservedly apologise. I have seen that situation and I think the sets have stopped growing before maturity and effectively remained as sets in the second year,if that makes sense. Don't stop wriggling though, I think I like it.

[veggiechicken]

Ooh you are awful, But I like you!!!

[Cue the Toms]

I think I put too many onions in my pot (15 in an ex recycle bin)... They have all taken well but can I transfer them or should I just let them get on with it?

[horticultural_hobbit]

And...the size of the onion, will depend on what you've fed it with. Something about stength and size being contingent on level of potash in feed.