We bought ours at our favorite local nursery -- Flowerland in Albany (which was also recommended by Berkeley designer Erica Tanov in the September '11 edition of Elle Decoration UK). These troughs come in different sizes (3-8 feet long), and they complement all types of spaces--from urban rooftop to country garden. They are especially great for growing bamboo, which can become unruly if planted directly in the ground.
Maybe it's the juxtaposition of the industrial (metal) vs. the natural (earth); maybe it's the contrast of the green against the silver. Any way you look at it, these are beautiful and modern alternatives to more traditional container gardens. Special thanks to Marco, our landscape designer!