PVC pipe planters
A vertical "Lettuce tower" made from PVC
This would be perfect for what I want to do. I have a fence around my backyard. I would like to attach 5 foot tall PVC planters like the ones shown above to each of about 5 fence posts. Then I can plant various greens and herbs in each of the many holes.
Watering might be difficult. It would be beneficial to have some kind of irrigation system because I wouldn't want to have to water it every day. Perhaps a water reservoir up on top with a cotton cord going down the PVC pipe to wick the moisture through the planter. Or maybe the planter could be fitted with a soaker hose.
One way or another, this is what I want to do. I haven't found a good enough tutorial on making this sort of planter, so I may just have to experiment on my own.
The "Garden Stick"
The Garden Stick is a commercially available PVC (I think it's made of PVC) vertical planting tube. I'd rather make my own, but the Garden Stick provides a lot of inspiration for making a vertical planter out of PVC pipe.
One of my favorites is this system using long lengths of 4" PVC pipe, mounted horizontally on posts, three levels high. The whole thing is fitted with a drip-irrigation system, and it can be clearly seen that the gardener is growing lots of herbs and greens. I like how placing the PVC pipe horizontally allows the plant to grow straight up rather than out the side of the pipe.
Here's a nice hanging vertical PVC planter that's used to plant flowers in. It's made of a short section of pipe and is hung by a chain. Enhancements include an inner pipe to route water to all the plants. Window screen covers part of the plant holes to keep the soil from falling out.