Shared front flower bed
I live in a townhouse which shares a small (about 5' deep, 10' wide) flower bed with one set of neighbours. It is bounded on the back by our shared stairs, in the front by the road, and on either side by our driveways. In the centre is a deciduous tree, planted about 10 years ago, which I guess to be about 15'-20' high and less than 15' wide. It is a fairly "airy" tree which provides only minimal shade when in full leaf. There are also three struggling deciduous shrubs (the fourth one died already; the original "foundation" planting of coniferous shrubs also died many years previously) and some creeping thyme that I planted to try (unsuccessfully) to minimize the soil erosion.
It is west facing and experiences extremes in temperature, wind and rain. It also is exposed to some foot traffic due to lack of barriers (or thriving plantings) which cause people to treat it like a lawn. In the winter it is exposed to road salt and also used to pile snow - several feet deep reaching the lower branches of the tree.
The townhouses are red brick exterior in a Georgian style.
Obviously, any changes would have to be planned and approved by my neighbours. As well, the garden needs to not rise the ire of the local board of directors or property manager.
My plan is to install a short dry stack border around the three exposed edges and raise the soil level. Right now, it slopes away dramatically from the base of the tree towards each driveway. (Another neighbour already successfully installed such a border a few years ago.)
A few questions about how to make this work.
(a) How to deal with the tree. I'm guessing that I need to mulch around the base of the tree. Given it's size, how big a diameter should I leave as a no-plant zone. Or, can I plant around the base? Maybe spring flowering bulbs?
(b) The shrubs. I wonder if I should try to convince my neighbour to get rid of them and start fresh. If they stay, I need a fourth bush to replace the one that died. Unfortunately, I've never been able to match the existing ones to anything I've seen in nurseries - even though these shrubs seem to be everywhere in foundation plantings. I could try growing a new one one from clippings, but I'm just not that attached to these shrubs to want to put that much effort into it.
If I did get rid of them, I'm leaning toward upright conifers, maybe junipers, but I'm not sure what would be appropriate given the conditions and the space available. I think I'm probably restricted to a somewhat symmetrical design, so this would likely mean two shrubs, one on each side of the tree, but further back.
(c) Flowering plants should make up the remainder of the bed. The board of directors is pushing more toward annuals, but I'd prefer a mix. However, I'm concerned about being too ambitious (and messy looking). Still, the flowering plants seems the best option for creating diversity yet still maintaining balance - repeating a couple colours, but layering heights and textures. Perhaps this year it might be best to stick with annuals.
I like the idea of blue and white or maybe blue and yellow (just a few for accents), but I'm not particularly artistic and don't know how this would look against the house or given the limited space. Suggestions would be appreciated.
Thanks for reading!