The Basics

There are numerous ways to build a vertical garden.  But here’s how we’ve been doing it at the Vertical Garden Institute:

Surface. We have built vertical gardens on two kinds of surfaces.  For flat gardens, we use “expanded PVC” sheets.  The PVC sheets are 4’x 8’come 1/8^th inch thick.  We buy them for about $28 a sheet from a plastics supply house.  For columns, we’ve used 55 gallon plastic drums, which are about 3’ high and 6’ around.

Frame. We’ve built a lot of stand-alone panels, on the theory that we could easily move them someday if need be.  On a couple of panels, we’ve used 2″x 2″ cedar with metal reinforced corners.  To date (October, 2010) all the rest have been constructed using a cheaper and more durable frame made of ¾” PVC pipe and fittings.  Some of our gardens have not used frames at all – we simply attached the expanded PVC sheets directly to masonry walls, using plastic mollies and metal screws.  We’ve not used metal frames because of the cost and weight.

Fabric. We’ve used a variety of non-woven, non-biodegradable fabrics.  Based on Patrick Blanc’s book and other research, we have experimented with several types of capillary mats, including “CapMat II,” or non-labeled rolls, as the cloth media.  These did not prove suitable because they did not absorb and hold water adequately.  The fabric we’ve adopted for use this year (2010) is a ¼” felt carpet pad that comes in 40’ x 6’ rolls (making them the perfect width for covering the 55 gallon drums).  We put two layers of cloth on the frame.

Mesh. On our tallest wall (18’), we screwed a plastic deer fence (quite strong) onto the surface and below the carpet.  We added this so large plants would have root support.  Don’t know if this is really necessary, but we did plant some things that can get pretty big.

Staples and screws.  We screw the cloth to the frame, using small zinc dipped self-tapping screws.   We use stainless steel staples.

Irrigation. We use drip irrigation emitters, of various flow rates.  For our tallest garden, we used 7 gallon per hour emitters.  For our others we’ve used ½, 1, and 2 gallon per hour.  We use a nominally ½ inch poly pipe, with fittings that allow re-use of an end without recutting (the brand name for the irrigation fittings we use now is “Perma-Loc”).

Pressure reducer and filter. We reduce our city supplied water pressure to 25 PSI.  When we use our pond water for irrigation, we use a disk filter system to take out the algae and other stuff.

Fertigation.  We have experimented with a number of different fertilization devices.  In our first growing season, we used an ebb and flow recirculation system, but gave up on that because of the maintenance.  In 2010 we’ve been using fertilizer injectors both large and small, which we use to inject a soluble 20-20-20 fertilizer into municipally supplied water.  We’ve experimented with different levels of fertilizer concentration, and had good success with a variety of concentrations.  We also have used “undosed” (no fertilizer added) pond water, and have had good results with that too.

Water Control. We are testing a number of different standard residential grade irrigation valves and solenoids.  We’ve tested a number of irrigation timers as well, and have developed some preferences for timer design (when you’ve got to constantly reprogram because of changing water needs, it’s nice to have a “clear” button!).  We over-watered our first year, and lost a lot of plants to root rot.  We under-watered this summer, and lost some plants to wilting.  We are seeking a low-cost way to control water flow based on water need (that is, turning the water on when the fabric dries out, as opposed to turning the water off when it’s raining), but we haven’t found one yet.  We’ve just started testing “propagation” timers, which allow a degree of control not provided by standard irrigation timers.

Plants. As Patrick Blanc has said about his beautiful vertical gardens, “it’s all about the plants.”  So true.  We’ll provide more info on specific plants elsewhere, but we learned the hard way that plants can survive cold in the ground far better than high on a wall.  In December 2010, the Pacific NW faced its coldest spell in many, many years.  All the plants at the Institute’s grounds were hardy to zone 8, the zone for the Willamette Valley in Oregon.  However, all plants rated zone 6 and above died, and many zone 5 plants also did not survive.  Based on this experience, for the gardens he planted in 2010, we have selected plants rated zone 5 or below (with a few exceptions).  The owners of Patrick Blanc’s first vertical garden in Tacoma, Goodwill Enterprises, published a list of the plants he had planted there in the fall of 2009.   The Institute’s 2010 gardens include about half of the plants used by Blanc on the Tacoma wall, plus a number of native plants and other choices.  Here’s a photo of the Tacoma Goodwill vertical garden, taken on a day in May 2010 when the owner’s gardeners were working the wall, which also suffered a great deal of winter mortality due to the extreme cold in December of 2010.