This is the tallest cortaderia that we grow. It reaches 10-12 feet, and is the one I like least - but it is seriously impressive. Needs a very big garden. The plumes have a pink shade but tend to become a bit straggly when its wet and windy. I've not been tempted to divide.
And this is my favourite cortaderia - Sunningdale Silver. Not as vigorous the others, growing to about five feet.
This is the most attractive cortaderia we grow, standing at about 6-7 feet. I have been tempted to divide this variety and probably grow too many. The plumes do not seem to be affected by the weather at all. They will look just as good at Xmas. All cortaderia foliage is dangerous and should not be handled without gloves. This variety seems to be the most cutting of all. So like so many of the things we find beautiful its best looked at rather than played with.