I would like to start by acknowledging that this is not one of my innovative, original ideas. This project is included because it is an example of using "feed trough planters" in a different way. There are a lot of images available of container gardening and feed troughs used as landscape accents. The success of our planters is the height of the end product and the resulting privacy screen.
I first became aware of this idea, years ago in Dwell Magazine's October 2007 issue. I saved the clipping and adapted it to my needs in May 2010. During our home renovation, we removed a decrepit lattice fence that enclosed our back patio. We felt exposed after doing this, but were not sure that we wanted another fence. The planters came to mind, as they could be used to form a visual perimeter around the patio delineating the large open yard, from the semi-private space.
Along the same time, I had removed a section of gravel driveway, yielding several yards of dirty road mix. The two projects collided and we decided to use the gravel mix as filler in the bottom of the troughs.
Since most evergreens do well in "poor" soil, it made sense to go in this direction for the project. We debated on the type of shrub, and ultimately chose Dwarf Alberta Spruce that were already close to their mature size at 5' tall. Adding these small trees to the 2' tall planter created a screen nearly 7' in total height.
There was not a lot of information about using troughs at the time, so I tapped out the drain plug and poured an entire bag of pea gravel over the opening to ensure adequate drainage. This has proven sufficient over the last three years and has yet to clog. After reading several other posts that suggest drilling out the bottom, I do not know if this is worth weakening the integrity of the container. It is steel after all and the containers are only plated.
The four planters have not aged at all and I am very pleased with how they look. They reference our exterior lights which are very simple galvanized fixtures. After three years, we have only replaced one of the original twelve trees. That was due to my stubbornness and using limited insecticides. Otherwise, this setup has been relatively low maintenance and the trees are quite happy.