In article ,
says...
Martin wrote:
You could try tasting one? That's pretty much how we did it. They looked
kind of done a week or two back, but they were still very very sour. Left
them for the extra 10-12 days and they were lovely.
If we leave them too long the birds eat them.

Odd, I don't think we've had any bird damage on the grapes. The buggers
nicked nearly all the cherries, and the wasps got a lot of the grapes that
went over, but I haven't seen any birds near the grapes.

Black birds fly into the tunnel to steal ours which are shouded in fleece
to keep them off at present.

There is a slight colour change when ripe but the taste test is more fun!
--
Charlie Pridham, Gardening in Cornwall
www.roselandhouse.co.uk
Holders of national collections of Clematis viticella cultivars and
Lapageria rosea