Spring green manure

[ameno]

Has anyone here (especially those who live in the South where it's a bit milder) successfully grown an early spring green manure?
I was look at my beds at the allotment today, and I realised that whole beds don't get planted up until around mid-May, when it's safe to plant out tender crops, and leaving them empty seems a missed opportunity (but I already have my overwintering crops in other beds). So I was wondering if I could sow a green manure in early March, then dig it in at the beginning of May. Would it grow enough in those two months of spring to be worthwhile?

[mothhawk]

Is this planning for next year? Phacelia grows fast and germinates well in March. But why do you want to sow in March? Can you not sow in autumn so it overwinters and protects the soil?

[nickdub]

Another well known one is grazing rye, which is usually sown in the Autumn when a patch of ground is cleared and then dug in in the Spring. It doesn't add fertility, but it does stop it being washed out of the soil by winter rains and adds a little humus.

[ameno]

Is this planning for next year? Phacelia grows fast and germinates well in March. But why do you want to sow in March? Can you not sow in autumn so it overwinters and protects the soil?

Because the beds in question usually have crops in until the first frosts, which where I am is usually November. That's too late to be sowing in autumn.
And yeah, it is planning for next year. Obviously it's too late now for a spring green manure.