In the last week or two there has been some worrying about how late mistletoe berries are whitening up this year – staying a milky-green for too long. But I was out looking at mistletoe yesterday and found lots of almost entirely white berries, so I don’t think we need to worry.
Much depends on which side of the tree you’re standing – on the south-facing, sunny side of the tree, all the mistletoe now has almost-white berries, whilst on the north-facing, shaded side of the tree, the mistletoe still has green ones. Berries on any plants in the middle of the tree are often green too.
Perhaps part of the problem, if there is one, is that some host trees held their leaves longer this year, extending shade longer than normal. But the wind and rain of the last week or so have taken off many of those last few host leaves and so that problem has gone (or is going rapidly). Nothing to stop full ripening now.