As a child in the South, I can remember many a neighbors' yard adorned with a tree with Blue Bottles instead of leaves. I never thought much of it until much later, after they seem to have disappeared from the American landscape.
The concept of these long forgotten icons of Southern Culture is actually very, very old. It dates back to the days when glass bottles were first invented, back in the early Iron Age. People developed a folk tradition that evil spirits could be trapped in these bottles. It is this tradition that started the whole Genii in a bottle belief as well. It was most prevalent in Africa, but also to a lesser extent in Europe. The European form mostly took shape as the "Witch's Balls" currently found in many gardens (e.g. gazing balls). It was thought the trapped spirit would be contained in the bottle during the night, and would be destroyed by sunlight when the sun came up.
These quaint bottles were a fixture of Southern life in America until about forty years ago. They were very common to find in most regions of the South, the tradition having been brought by the slaves and their descendants. Seen by many to be part of the charm of the South, they are rapidly disappearing as the Old Ways are being overtaken by Ipods, Cell Phones, and our culture of immediate consumer gratification.