8-10 feet with large orange/yellow flowers eh- do you have a pic?

I don't think you could over water them if you tried. I stick rhizomes under the rocks in my pond and they love it. Canna are simple- lots of sun and lots of water. Just be careful not to spray directly on the leaves while the plants are in direct sunlight or they might burn.

I'm also new to cannas. Since you said they love flower, does it mean that I have to water them like 5 times a day?

No, they do love water but it's really up to you how much you give. I have my 'special' canna (e.g. stuttgart, cleopatra, striped beauty, etc) that I water every chance I get but most of them I just let the rain do the work.

Becca welcome to canna gardening. Seems like you got very lucky and inherited a nice canna garden.

The plants you describe are probably Musofolia or Omega. The two largest canna variety. I have found that canna, especially those, are not particularly happy with super hot weather. I think when the temps goes above 95f or so, they stop growing and may even get a little distressed.

But don't worry about that, just give them water periodically. Every couple of days a good watering should do it. Adjust that as you see fit.

As for taking care of them in winter... When the temp drops below freezing the canna leaves will all die. Just cut them to the ground and toss the dead stuff. Under ground they have dense rhyzome bulbs that will regrow in the spring.

Since you have so much canna in the ground now, I think it's safe to say that they over-winter well in your location.

Lastly, if you really enjoy canna gardening you might look at diversifying your beds a bit. In the spring, dig out some tall plant rhyzomes, before they start to leaf, and find someone who wants to trade short to medium sized canna for your tall canna.

Throw some shorter, different color canna, like red canna, in the front of your tall ones and you'll have a small tropical wonderland right there in your yard.

Good luck!