How many kilograms of leaves does a comfrey plant make per year?

Hi Ash,
That's a toughie.
I have used comfrey liquid feed for many years, but never give the weight ratio a thought.
There are several types of comfrey, and I grow the prostrate one mainly as ground cover. I can do this because we live on a little lane, so it is growing under the hedges where little else will grow.
I use an old large brewing bucket.
So I tend to go off colour.
Banging in handful's to keep it right.
The leaves themselves are very light as you already know.
Which could be quite a lot for a kilo.
It is all dying away at present.
I will clean it up soon and put the residue in the compost bin.
I don't know how well it works, but at least nothing has died from using it.
Pete

I know Monty Don had it on 'Gardeners World' a couple of weeks ago.
And he was going off a 10 to 1 ratio to use in the can.
As it can no doubt vary quite a lot, I would think that that is somewhere around the correct ratio. So comment from Lardman sounds like it is in that range.