I have now officially added cannas to my list of Plants That Will Never Grow For Me Anywhere. This is the third garden at which I’ve tried them with either zero or pathetically minimal success, but I do wish I could figure out what I’ve been doing wrong. I’m in Zone 7 (either a or b depending on the particular winter) so they are tender tropicals for me.
Attempt #1 was in my first garden, in what should have been optimal conditions of full sun and lovely friable loam in a slightly sloped raised bed. This was the same bed that had been home to such marginally hardy divas as a Eucalyptus perriniana for several years until a bad winter killed it, so cannas-as-annuals should have been a piece of cake. Having been impressed (okay, overwhelmed) by a huge canna display at the entrance to Longwood Gardens the previous year, I bought a half dozen tubers each of ‘Black Knight’ and that shameless hussy ‘Cleopatra’. Planted them according to instructions but Cleopatra must have sailed down our canal to the Nile when I wasn’t looking, because not one of them ever broke ground. As for Black Knight, most of them went along with her except for two who barely managed to struggle up to 24” high and would have been more appropriately named Black Wimp.
Attempt #2 was in my third garden, again in full sun but not in a raised bed and in somewhat richer soil. I went with six ‘Pretoria’ tubers this time. Two came up and were promptly chewed to death by something (probably rabbit but possibly squirrel) before either could flower. I have a sneaking suspicion that I might have planted those a bit too early; I went by the calendar (mid April) rather than by soil temperature.
Attempt #3 was this year here at the Money Pit, as an impulse buy of a pack of three tubers of ‘Tropicanna’ and also of ‘Picasso’. This time I waited until May to put them in the ground. As of today, the third week in June, this is what I’ve got. Of course the one I most wanted to see is ‘Tropicanna’ which should be coming up behind and slightly to the left of Picasso but obviously is not making an appearance at all.
So I guess I should give cannas the “three strikes, you’re out” treatment and probably will, except for the fact that next spring I’ll have a nice little paved courtyard area that (now that my neighbor’s overhanging Oak Tree From Hell is gone; yay!!!) is going to cry out for a couple of big containers of tropical-looking plants because it will be a sun-trap most of the day. I have been musing upon one of those big elephant-ears (Colocasia), Curcuma ‘Sweet Memory’, and possibly – just possibly – one final shot with a pot of canna.
But if I do try, and they canna’ grow for me even in that way, I really WILL give up!
The Chatsworth Lady 
They can be such weeds where they get water. I don’t meant that in a bad way. They just get a bit more prolific than expected. The prettier ones are tamer. They do not often spread by seed, but their rhizomes are quite vigorous.