Yep, those are banana trees, here you simply stick them in the ground and they grow back every year (they die back usually in November, or December in southern BC, depending on where you are, when the temperature drops below -2 C (28 F) for the first time). So all growth there is one years worth of growth. But here their roots don't freeze.
Last year, during our really hot summer, some people actually had a few bearing fruit (of course really small), such as my neighbors down the street. Our long frost free season helps them a lot.
There are two types that can grow here though, the first is the pure green one (the most common) and it is the most hardy, and that is likely the one you see in Delaware. The other is the one with the mixed green / purple leaves you can see in a couple of my pics, they are less frost hardy but still do fine here.
Obviously all of the exotics here are outside year round (many of my pics shown are taken in early March and early April for example).
Many of the windmill palms shown have grown much larger over the past 10 years (when i first started taking an interest in them) A few of them, as shown in a couple pics, are approaching 30 feet tall.