Narrow/Shallow amount of Soil available - OK for Rose of Sharons?

 I live in a home that has a two car garage butting up to my neighbors
2 car garage. Our driveways meet.

There is a 5 inch wide space between our driveways that runs the
entire length of the driveways. It is filled with soil about 6 inches
deep. In this narrow space there are a few - what I think are Rose of
Sharons - that are planted in this narrow space. They appear firmly
rooted.

I want to plant the entire length of the drive in the rest of the
narrow space to provide a screen between both driveways but I dont
know if this is the right plant for that small of space. I know Rose
of Sharons grow tall and like a vase, so I think the root ball must be
small.....but 5 inches wide by 6 inches deep....is this enough to get
a ROS root ball into and fill? I still cant figure out how the other
ROS's are planted there.

Any other ideas for a type of tall fast growing plant (doesn't need to
be an evergreen, but that could be better) that will get good morning
sun but filtered and mostly shaded in the afternnoon and has a very
small root ball?

I'm really curious about the planting root ball requirements for the
ROS's though, this puzzles me.

 
I don't think that much that grows tall can grow in that little
space!  They must have really strong roots under the covering of the
driveway!  Wow!  Okay, back to a suggestion, grasses - there are
several ornamental grasses that grow tall and are beautiful all year.

just an idea.

dancing in my mind,
gloria in hemlock hollow where all the wondrous flowers will disappear
tonight. - down to 25F

 @y80g2000hsf.googlegroups.com:


Whatever you put there is going to need WATER.  How are they going to get
enough?  The more plants you add, the more competition for whatever water  
manages to get through.  You're going to reach critical mass very quickly
and everything is going to die.