The most common plant around here is ragweed and smartweed, as they eventually take over the area once the enthusiasm for maintenance is over.

But before the smartweed comes, islands are planted with rugosa rose and stella d'oro, as you have mentioned.

There was an earlier thread on this same topic I believe back in Feb of 08 but here's what I recommended the last time: Prairie Dropseed (Sporobolus heterolepsis) - an attractive lower growing native grass approximately 2 feet high - turns a lovely golden yellow in the fall and is small enough not to obstruct traffic and is drought tolerant once established. You could make a simple elegant statement and populate one or both islands with simply this grass.

Daylilies are nice and they are cheap but they require several deadleafing sessions after they bloom to look their best plus an an annual fall cutback whereas the Dropseed requires only a spring cut back. I think you'll save more money on the maintenance with the grasses.

1. Think safety - don't block vision.
2. Think resistence to damage - vehicles, salt, sand, polution, & snow removal.
3. Think maintenance - watering, pruning, annual vegetative cleanup, trash accumulation and removal (rugosa roses, not fun).

Low ornamental grasses are a good choice as Gonative mentioned. They they recover from physical damage almost as well as herbacious perennials and are very dought tolerant and tough - inexpesive as well.

don't know how useful this info will be, considering that I'm in the hot DFW area, but some cities in my area have had success with

red yucca (drought & heat tolerant, evergreen, no maintenance at all)

nandina, don't know the variety

something that I *think* is a Peruvian lily, but this would have to be in the center of a wide island, as it's huge.

bearded iris, evergreen, no maintenance, no mulch over rhizomes

salvias, don't know the names

For ornamental trees, they use

crepe myrtle
Magnolia
desert willow
Chinese pistache

Best luck!

Is anyone familiar with plumbago - just got back from
Florida and it is so pretty there. I read that it is
a shrub there but would it grow here ?

Dwarf plumbago does great in zone 5b in New Mexico's high desert, I know that much...

It depends what cultivar you are looking for ceratostigma (leadwort) or the bush variety common down south. Leadwort would not be a good choice for a traffic island as it greens up late in the season, and it is not good a weed suppression.

The check the USDA zone on the bush variety, as I suspect it may not be hardy in TN.