This is a detail of a wall garden was in Parkdale, the west side of downtown Toronto. There was (and still is) quite a crack issue on this corner. The white door in one of the photos led to my apartment on the second floor, and the plants made things saner.
The cans used in this project are recycled pizza sauce cans from a takeout restaurant (the 2 4 1 on the corner of Queen and Landsdowne, in fact, and a great slice of pepperoni they make, too!)
The restaurant cans are much larger than anything you would buy yourself and recycle - these cans are 1 gallon, the size of a can of paint. Anything smaller, you'll have to water every day. Pizza restaurants go through dozens of these cans every week, just ask.
Painted with rust paint these looked pretty good for two years, the third year I did touch ups on the rust that was showing.
Kinda toxic process - not recommended for edibles, but oh so gorgeous for flowers. Rust paint comes in a dozen colours these days.
The cans are attached to the wall with wire.
DO IT YOURSELF:
First, punch two small holes near the top of the can with a nail or screw. Use a piece of wood to support the edge of the can, position a nail on the metal, and hit with a hammer. The metal of the can is pretty soft. Punch TWO holes to help the can hang straight vertically.
While you're at it with the nail and hammer, turn the can upside down and punch some holes into the bottom - 4 to 5 holes.
Next, use a regular drill bit to make holes in the wall. (Brick is pretty soft, the mortar even softer.)
Hammer in a drywal plug and screw in a screw leaving about a 1/2 inch of the screw sticking out. (If you decide to remove the cans later, the holes can be easily filled with colourmatching silicon putty and become basically invisible in the texture of the brick.)
Next, prepare the hanging wire. Cut a piece of wire, bend in half, and thread from the OUTside to the INside of the can.
Wrap the wire around the screwhead in the wall just once or twice, and position the wire ends behind the can. (Don't cut the wire, just bend behind - it makes taking the can off for winter storage easier.)
Straighten the can to hang vertically and screw the rest of the screw length into the wall to tighten on the wires.