Rose of Sharon (Hardy Hibiscus

The shrub commonly called the Rose of Sharon bush, which is not a rose at all, is actually part of the Hibiscus family (Hibiscus syriacus) and yet can grow as far north as Zone 5. Some of the merits of this plant to take note of, besides being very hardy in cold climates, is its form, array of colors available, and its over all toughness, taking many different light conditions and soil conditions.
I have one in my yard now that is in almost complete shade and it still looks wonderful. Bright green leaves, healthy looking shape (not leggy), and it even flowers, a little. This years blooms I could probably count on my two hands, but I don't mind because it is a nice specimen in a shady spot not much else could grow in.
I have another in a more sunny spot, but probably only half sun, and it blooms great, looks great, and even the form in the winter is appealing. It has a spreading upward habit, and on the ends of many of its branches are the dried flower bud casings (the part that surrounds the bud before it blooms).
One note worthy thing to add - the deer do not eat these! This is cause for praise indeed.
Now, besides the two in my yard, I have worked with these a lot and there are lots of different cultivars. Some are larger than others and some are more profuse bloomers than others, some even have double blooms rather than the single bloom common to the species. I have seen this plant used as a blooming hedge, and also as a distant plant of interest. When I say distant plant of interest, I have known people to tuck them into a distant wood line, and you never notice them until they bloom. I have also seen Japanese Kerria's used in this way, as well as many other beautiful plants that are sometimes too messy for a formal garden, or too large.
Rose of Sharon are rather large, and so therefore have to be planted in a place that anticipates the size. I have seen people buy this at the garden center in a cute little one gallon pot, bring it home, plant it by their front window and in 4 years it is eating the front of there house (not literally, just blocking the view and branches plastered up against the siding). So they cut it out and have to start new. If that had bought something size appropriate, they would have made a better investment.
Enough of that though, you realize it is big, here is how big the average Rose of Sharon grows to: anywhere from 4-6 feet all the way to 8-10 feet. That is not an exaggeration. Some even get as tall as 12 feet, but they a can be pruned to shape them as a hedge, not a tidy hedge like a privet, but a more loose hedge. Just mind when you trim, or you will cut off all your flower buds. Best time to prune is after flowering for sure, but wait even into the fall or winter when the plant is dormant. It blooms on new growth, so when it wakes up in the spring, it is too late unless you want to lose the years blooms.
Now, on to some of my favorite cultivars in this species. There are a lot to choose from, even a tricolor, which is actually one plant with two other colored Hibiscus grafted in, giving the impression that one plant is blooming in three different colors. Not one of my favorites, but here are some that do hit the mark with me.
'White Chiffon' - double white (I do not typically like white flowers, but these are beautiful)
'Aphrodite' - pinkish purple single bloom with a red center
'Lucy' - double pink blooms (one of the most beautiful I think)
'Collie Mullins' - double lavender blooms
Those are just a few of the cultivars available.
One thing I was reminded of just now. Some people consider this an invasive species of sorts because the seeds are viable (fertile) and can be spread around by the birds. I have found however that they are not that numerous (the seedlings) in my northern region and can easily be pulled up. If you mulch your beds they are even easier to deal with. In my opinion they are no more invasive than a sugar maple. When they drop seeds you  see a flush of seedlings some times, but the majority of the seedlings do not survive the summer heat, and the ones that do can easily be pulled up.
A note of consideration though, I am in a zone 5/6 and so on the colder end of things, in the southern regions they(Rose of Sharon seedlings), but I do not know for sure. Consult a local garden center if you are concerned.