Pam, 'Caradonna' has been 'doing the rounds' for a few years now and
is quite widely available so you should be able to track one down in a
local garden centre. It is possibly the best of the nemorosa
cultivars and from a grower's point of view it makes a good 'potful'
very easily. This means you can buy a very nice 3L plant for around a
fiver that will give a really good show this summer and get better
year after year.