I wanted to build a vertical garden that I could attach to my fence, but with planter boxes that were removable so I could more easily share the gardening experience with my 3 year old. Unable to find specific plans online, I made my own, inspired by images found online that didn't have any instructions.

The end result is a 5' tall, 6' wide frame that can hold up to 9 planter boxes using a french cleat mounting system.

Step 1: Materials:

3 - 5' long 2x4s

4 - 6' long 2x6s

5 - 5.5" wide cedar fence pickets (less than $3 each from Lowe's)

Finishing nails

2 to 3" wood screws (I used deck screws since I knew they'd be well suited for outdoors.)

While a table saw and miter saw would be nice, I managed everything with just a circular saw.

Step 2: Planter Boxes:

(Note: In retrospect, I wish I had made the boxes a little deeper. However, I'll give instructions for what I actually did.)

The wood listed in the materials section provides enough to make 5 planter boxes. However, the frame is able to support up to 9. For each additional box (and cleat to go with it), you will need 34" of 2x6 and one cedar picket.

For each box:

Cut two 5.5" squares from a 2x6. Along one edge, cut in at a 15 degree angle. (Miter saw would have been nice for this.)
Cut two 23.5" lengths from a cedar picket.
Screw one length of picket across the straight side of the 2x6 blocks. This picket will be the back of the box while the blocks will make the sides.
Screw the other picket on the angled side of the blocks to make the front.
Orient the box so that the narrower opening is the bottom of the box.
Measure the inside width (block to block).
Cut the remnant of the picket to this size. Should be roughly 19-20".
If the angle was done correctly, you should be able to push the bottom picket down into the box with a snug fit. On some of my boxes, I actually needed to use a rubber mallet to tap it as far down as possible.
Once the bottom is snug, use finishing nails to secure it.

Once the boxes are all built, set them aside.

Step 3: French Cleats:

This design uses french cleats to make the planter boxes removable. One of the 2x6 boards will be used horizontally on the frame. A second board will be cut into smaller sections for the planter boxes.

Along the length of the board, measure 2" in and draw a line. Using a table saw or circular saw, cut along that line at a 45 degree angle for the entire length of the board. This should give you two identical 6' long sections.
Repeat on two more boards.
Set aside three of the 6' cleats for the frame. Use the remaining cleats to cut five 23" long sections.
Screw the 23" cleats on to the backs of the planter boxes. Pay attention to the orientation of the cleat. Use the images as a guide.

Step 4: Assemble the Frame:

Lay out the three 2x4s on the ground, 6 feet across on the outer edges, with the middle board centered at the 3' mark.
Measure 13" up from the bottom, and attach one of the long cleats across all three boards. Pay careful attention to orientation.
From the bottom of the first cleat, measure up 20". The bottom of the next cleat goes here.
Again, measure up 20" from the bottom of the second row. The bottom of the last cleat goes here. This will leave a few inches right at the top where the planter boxes will go.

Step 5: Final Touches:

I wanted to keep my vertical garden as simple and modular as possible, so I decided to avoid putting any holes in my fence when mounting the frame. Instead, I just got some heavy duty zip ties and strapped the frame to the fence.

Since the bulk of the weight will be straight down, the zip ties should be plenty strong enough to hold it up. This is also nice if you don't own the structure you are connecting to, or if it's a chain link fence or something.

Now just fill up your planter boxes and hang them on the frame!

Step 6: Tips and Thoughts

I'm currently working on some sort of semi-automated drip watering system, since vertical gardens tend to dry out very quickly and otherwise require daily watering.
Squirrels are vicious little monsters hell bent on destroying my efforts. I found a lot of different suggestions to keep them away. So far, I've found success with adding spicy pepper flakes on the soil, and pointy bamboo skewers sticking up out of the soil in different directions. So far, so good.
I mentioned above that I wish I had made the planter boxes deeper to give the plants more room for roots. I'm open to suggestions for a better box design.
This is the first project I've designed for myself, and would love suggestions as to what I could do better next time.