green manure ?

Hi all,I have three beds that are almost empty 10ft x10ft,the have had spuds, onions and garlic in , poor show on the onions.I was thinking of putting some green manure in but Im not sure what to sow,and will it be invasive.As you see Im a bit new to this and would like any help.Thanks

I've sown this in a couple of beds yesterday.

http://greenmanure.co.uk/winter_mix.htm

Spudman

IVe pit down some red clover on tues , hope it doesnt take to much digging in.

This year Ive sown mustard in 1 empty bed and phacelia in another 

Both have just germinated.........but my broadcast sowing is very patchy 

Oh dear me too - broadcast sowing skills are about par with straight line skills 

I've been up to the plot today and had to oversow my mustard green manure to hide the bald patches