Red onions

[dave45]

Always seem to come out smaller than regular yellow onions? Why is this? What is the secret to getting big red onions?

[Weedo]

For me using a wider spacing at 150mm approx and using soluble fertiliser rather than compost etc. Onions don't seem to like much organic matter. I discovered the wider planting technique this year when the cockatoos and galahs ate 3 out of 4 plants.

However, we grow diferent varieties (short day to intermediate) here than you would so the rules will be different. We plant May / June (end spring) for December harvest.

[Odsox]

I can't comment on red onions as I don't grow them due to their inferior keeping abilities, but I can confirm Weedo's point that onions prefer liquid fertiliser.
I start mine off in cells, multiple sown roughly 3 to a cell and plant them out close spaced as I actually want smaller onions. During late spring I start watering them with liquid seaweed once every now and again when I remember and that really gives them a boost.
I still get quite a few that are too big for my liking, but the majority end up about tennis ball sized, plus a handful pickling sized.