Dianthus'es

Went to a garden centre to buy a garden but they didn't sell any.

So I bought some little bedding plants that would be useless as a pillow or a duvet . 

I saw this butterfly fluttering over the dianthus and wondered what the plural of a dianthus should be - dianthi? dianthus'? dianthuses? 

I think that maybe it's a 'Pieris Napi' but I couldn't peer at it's nappy because it wasn't wearing one. It's also called a green-veined white - if I'm right.

And I'm a little sad that I can't get macro shots in good focus. Perhaps my camera needs glasses too.