This farm garden wall, build at Headwaters Farm in Colbourg, ON, is based on permaculture principles. See Video. 100 linear feet becomes 1,700 feet of planting surface. The wall is built beside the barn where water can be collected and diverted along the top of the wall with an irrigation hose.  More photos below.

The vertical wall is built beside the barn to capture water from the roof.

Growing strawberries and flowers.

Growing surfaces on both sides offers different micro-climates for growing different plants.

The ducks and chickens eat from the lower levels.. the "people food" was out of reach.

Another view..