How to start a vertical garden

Build a frame

The basic structure of a vertical garden wall is a three-layer sandwich made of frame, plastic sheeting and fabric. Build the whole setup before hanging it. While you can attach a vertical garden directly to a wall, Yates says building a frame to hang on the wall means taking it down will be much easier. 

Yates uses three-quarter-inch PVC pipe, elbows and four-way joints to build a frame. He advises against using metal, because of the additional weight and expense, or wood, which requires pressure-treating to protect against moisture rot; you don't want water trapped between a wood wall and the plastic frame.

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Attach plastic sheeting

Attach a sheet of plastic to the frame. The plastic acts as a backing for the fabric layer and keeps the water off the wall. Yates uses expanded PVC sheets. (Note: If you want to try this on a wood wall, you'll need to ventilate behind.)

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Attach the fabric

Attach the layer of fabric to the frame. This is the material in which your plants will live, and which will hold water for them. Yates has used basic felt carpet padding, but he says that you can use just about anything that will retain water without rotting. 

You'll need at least two layers of fabric. Attach them directly to the frame with galvanized screws and stainless-steel staples as if you were stretching canvas across a frame. As long as the fabric is secure and taut, with no buckling or wrinkles, you're good to go. "You just need to attach it some way so it doesn't come off and it looks pretty," Yates says.

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Set up the irrigation system

To keep plants growing on a vertical surface, you'll need an irrigation system that can provide moisture throughout the fabric layer. You can make one out of poly tubing with fittings that lock; Yates uses Perma-Loc irrigation fittings. It's basically a tube across the top of your panel with emitters that drip water down. Your best bet is to get them from an irrigation supplier. 

You can buy a standard valve and irrigation drippers, but you'll need a propagation timer that can be set for seconds rather than minutes. You want a quick flow of water for 10 to 15 seconds three to six times a day, depending on weather conditions and your particular setup. Attach an emitter every 2 to 3 inches along the top irrigation tube and experiment to find the right balance between keeping the wall wet and not overwatering the plants. 

Attach the frame to the wall using stainless-steel hardware, to avoid rusting. Hooks are fine if you think you'll want to remove the frame; otherwise, brackets screwed into the wall and the frame will work.

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Add fertilizer injector and attach irrigation system to water source

To fertilize your wall, attach a fertilizer injector, such as Add-It, with a simple irrigation valve that sends liquid fertilizer into the irrigation system. Then hook up the irrigation system and connect it to your water source. You'll need to filter the water with an irrigation water filter, which is cheap and available at most hardware stores. 

Remember, there will be some runoff; one way to deal with it is by planting a flower bed underneath your vertical garden.

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Choose your plants

As with any gardening, take into account sun, shade, humidity, wind and cold when choosing plants that you're going to leave outside all year. If you intend to leave the garden out during the winter, Yates recommends selecting plants for a colder zone than the one you live in. For example, Oregon City is a zone 9, but Yates plants for at least zone 6, and usually in the 3 to 5 range. 

If you're building a detachable wall and planting it with evergreens, you could try storing it in a cool, dry place for the winter while the plants are dormant. 

Some plants that have done well in Yates' walls are hostas, iberis, phlox, ferns, weigela and even blueberries. "Native plants seem to do better than nonnative," he says.

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Insert plants

To insert plants into the outer layer of fabric, use a razor blade to make a horizontal cut in the material. Get as much soil off the plant's root ball as possible, to help stave off root rot, and insert it into a cut. Using a staple gun, insert three to five stainless-steel staples to attach the cloth to the plastic backing in a semicircle around the root ball, creating a secure envelope.

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Plant design

The fun part, Yates says, is designing your plantings, and the height of a vertical garden offers lots of possibilities. 

Choose plants that will grow 2 to 3 feet out from the wall, and plant them at the top so they create shade underneath. If you do this, though, keep in mind you'll have to plant shade-tolerant species underneath, such as ferns. Also, a plant that's 8 feet off the ground will often droop, Yates says. That gives a nice waterfall effect but also smothers whatever's underneath, so you'll have to trim it back. 

Planting in vertical strips, with green shade plants in one strip and sun-loving flowers in another, is a good idea. "If you're going to do this and have the most dramatic effect, and want your friends' and neighbors' jaws (to) drop, you need to get above their heads," Yates says. "They need to look up at a plant they'd normally see at their feet."

• Video: Vertical gardens around the world

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• On our blog, 'Listed': Here's a wall you can eat