It can be done and is being done to new and existing buildings across the world today. Of course they had to give it a catchy name: Living wall. They added one to the building I work in. It is 30 feet high and needs a mobile lift to let the gardeners tend to it.
For a do it yourself project there are a number of key issues that must be addressed or you could end up ripping it out or even causing water damage to your home.
- natural or artificial light in reasonable quantities is a must. Depending on your location and orientation it could be enough to have a south facing bank of windows, perhaps with some skylights. Or you might require a more robust light source like HID lights.
- water: plants need it and you need it to stay where you want it. Many installations treat their water to even out the ph and lower levels of dissolved salts and remove chlorine. (think what hard water does to your fixtures). Then the water is pumped to the top of the wall and released at very low pressure so it moves by force of gravity down to the reservoir. Problems can occur if the water does not flow in an even pattern along the outlet pipe. Wet soil can also slump downward if not held by a mesh. The reservoir should be treated like a pond. Use Pond liner or galvanized steel with a marine grade epoxy coating or both! No one will be happy if your reservoir leaks into the floor below!
- types of plants: pothos or creeping fig (ficus pumila) are easy choices but using bromeliads as they do not require a soil based medium is another approach. You should have a plan to deal with insects like mealybug or spider mite. Soap and water might not work for all the pests and rip out and replace is time consuming and costly
- environment: Most people like temperatures around 70 deg F or 20 deg C, humidity less than 50% and diffuse light. Your plants will be a lot happier and healthier with higher humidity and light levels some would consider too bright to sit in. Is the location suitable for bright light and higher humidity?
- construction details: different approaches are used but the idea is to retain the soil using a mesh of some sort with a grid/grill behind it. Avoiding leaks is paramount! Pool liner is your friend here.
Edit:
Sure you can put a planter up high and plant it with some pothos. It is a reasonable question to ask how often you will water it if it is difficult to get at. Care must be taken or water could splash out and down the wall. However if you want a project that you can do for less than $25 that fits the bill. I assume there is some insulation where the planter would be as 50 deg F is a bit chilly for a tropical.
