As long as we are on the subject of small spaces and small gardens, here some more pictures. First, balcony photos from Barb out in Las Vegas. These are their former Hawaii condo's two balconies. Just the right amount of plants to create a peaceful, little refuge. She's doing the same in their current desert abode. Perhaps I can post those photos later.
The next photos are courtesy HGTV Gardens.
How about this garden for a narrow space: Trellising Jasmine.
Or perhaps the only space you have for a garden is on your steps, or
The only garden I had at my little cottage apartment in La Jolla many years ago was half an old whiskey barrel beside the front door, that I planted with wildflower seeds. I loved it.