[18Forts1999]

I have grown a Green Manure this year (White Mustard 'Tilney') which is about one foot high now. Should I dig this in before the end of December or will it be OK slowly growing over the winter ready for digging in later. I have a clay soil. The beds this is growing in will be having brassicas and potatoes in next year.  This is the first time I have used a green manure so any advice would be most welcome.
Thanks

[cadalot]

On Line it says

"Sow the seeds at a rate of Appx 5 grammes per square metre where they are to grow from March - September.
Turn the plants into the soil prior to flowering for the best results."

Already cut mine down as they were starting to flower have left it laying on top and will turn in when I get around to it
 

[JoshP]

Leave until they start flowering, then cut down and dig in.

[gremlin]

Mustard is a brassica, so to follow with another brassica is not ideal....but why worry 

As I remember, digging it in when it is still green and soft is bit easier then next spring when the remaining stalks are woody.  I prefer to leave a cover crop over winter, even if it is just the roots, to protect my soil.  Depends what you are growing it for really:-  bulk organic matter or to protect the soil over winter.

Of all the green manures, I like phacellia the best.  Quick to grow, lots of bulk, lots of bee friendly flowers, very easy to pull up.