BS, 1 per square; turnips 4 - 6 depending on size
Here's and intensive gardening link with a chart for spacing:

Here is a link that might be useful: intensive gardening

Thanks for the information. ccgramma

LOL more like, how many squares per Brussels Sprout?
I grew Brussels Sprouts in my SFG the first year, along with cabbages and broccoli, and mine were way bigger than was practical in a SFG... the broccoli shaded out the adjacent squares, and the cabbage overlapped the adjacent squares with leaves, and the Brussels Sprouts were monstrously huge.
Wonderful, but huge. More like small trees.

So I am growing them again this year, but this time, elsewhere than the SFG.
Although the Earliana Cabbage says it is very small and good for limited space gardens. Also early, so you don't take the square up all season long for the one harvest.
hth,
Meg

I agree with Meg...

Last year I plant stuff willy nilly using different squares and I too found that Brussel Sprouts, Cauliflower, Cabbage etc tended to do well but overpowered the adjacent squares.

This year I am going to plant them in sections and see how that works.

Here is a picture of the root system of a brussels sprout in relation to the square.

You can see why it sucks the nutrients from the adjacent squares.

So glad someone posted this! I was planning on two brussels sprouts, four cauliflower and three or four broccoli in 10 squares - Having never grown any of them, I had no idea how big they'd get.

Do you thing the brussels sprouts would do okay in 5 gallon containers? Then I could do the eight broccoli and cauliflower plants in 10 to 12 squares instead.

I'm not sure what all the problems were with brussels sprouts, but I had no problems growing one to a square. They grow up, not out in my experience.