Living Walls are a growing trend that shows no signs of slowing down. From the superior aesthetic compared to drywall and paint, to the utility of growing an edible wall, it’s a trend that is easy to get behind. Imagine a wall covered in fresh herbs, lettuces and peas ready for the picking. The sights and aromas of such a wall will add style and literal taste to almost any residential living situation. And to top it all off, an edible wall will also add significant nutritional value to anyone lucky enough to partake in its fruits. It definitely beats the nutritional value of drywall and paint chips!
A thriving living wall does not have to be a tedious chore or onerous undertaking either – a living wall can easily be irrigated by an automatic drip irrigation system, leaving you more time to enjoy the things you want. A drip irrigation system for a living wall doesn’t need to be anything elaborate and expensive, either. Just some tubing, fittings and a dripper or two for each plant or pocket on the wall. Most living walls can be irrigated very inexpensively with high quality drip irrigation components that provide all the best benefits of drip irrigation – hyper-efficiency, durability and ease of use.
Irrigating a living wall with drip irrigation is straightforward, whether it’s for the felt pockets type or plastic container type. There are multiple drip methods you can employ depending on the type of living wall you have, the types of plants grown and the substrate used. The various methods used are also very similar and effectively perform the same function: efficiently deliver water to the plants in the living wall so that each receives sufficient but not excess water. Below I will illustrate and discuss a few of these methods. You will notice their similarities and see that it’s not a complex task that can only be done by the pros, but something even a beginner DIY'er would have little trouble with.
Before we dive in, let’s discuss a few of the benefits in having a living wall. Whether commercial or residential, a living wall can improve the aesthetic of any venue or locale to a significant degree. Though the advantages of an increased aesthetic are difficult to quantify, research indicates that they include increased creativity and increased productivity (up to 15% in some studies!).
Aesthetic improvements are often more than enough to motivate an individual, but the benefits of a living wall go far beyond mere aesthetics. In the US, millions of dollars are spent on air purifiers every year: individuals, businesses and military spending on air purification has increased significantly in recent years. While a living wall won’t fully replace a HEPA filter, it can certainly augment one to a great degree, and the evidence is compelling.
We already know that plants take in carbon dioxide and provide oxygen, but the actual possibilities are no exaggeration. Consider this: only 10.7 square feet of living wall can remove approximately 5 lbs of CO2 from the air per year. In addition to this, plants remove other airborne toxins, effectively acting as a living air filter. Furthermore, there are studies that indicate that the microbes found in soil substrate absorbs harmful VOCs (Volatile Organic Compounds) and convert them into substances that plants can use for food. This process is often referred to as phytoremediation.
As if those benefits weren’t enough, living walls can also improve acoustics. This applies to both indoor and outdoor living walls. Indoor living walls decrease the reverberation time of sound, while outdoor living walls can dampen many of the noises found in an urban setting.
Outdoor living walls have been found to increase the biodiversity of an area, attracting beneficial insects such as bees, butterflies, ladybugs and lacewings. These insects are known to eat harmful insects and their larvae, protecting not just the living wall, but other nearby vegetation as well. Anyone who has suffered an aphid infestation can tell you what an asset these beneficial insects are to any garden or growing space.
Living walls, both indoor and outdoor, can be used to help with temperatures, both internal and external. Outdoor living walls absorb significant quantities of light that might otherwise serve to heat a building and its surroundings. In addition to providing shade, they also cool the surrounding area through the process of evapotranspiration. On the hottest of summer days, the impact is substantial: temperatures have been observed to be up to 50°F cooler than nearby fully exposed buildings. During the winter months, a living wall can act as an insulator, trapping desired heat inside of a structure; this can lead to reduced energy use and associated costs. Finally, the reduced UV exposure reduces building maintenance and the degradation of building materials. Maintenance is further reduced by reductions in erosion from wind and water, and reduced thermal contraction/expansion from rapid temperature changes.
One of the understated advantages to a living wall is that you can fill it with edible plants. This allows someone to grow edible plants year round. Herbs, vegetables and even some fruits and berries can be grown on a living wall, giving you access to fresh food and spices year round. This in addition to the previous stated benefits.
Popular foods to grow in a living wall include: strawberries, lettuces and similar greens, beets, radishes, and some dwarf varieties of peppers and tomatoes. Herbs of all types can be grown in a living wall, from standard herbs such as oregano, dill and cilantro, to more uncommon herbs such as stevia, borage and anise.
When growing an edible living wall, some supplemental light may be needed depending on your geographical location, particularly for indoor living walls during fall and winter months. However, when growing conditions are reasonably similar to the plants normal conditions, you can have a vibrant healthy edible living wall year round, indoor or outdoor.
Living walls do not come without some risks, however. As plants, they do need water, and water and indoor environments do not always mix well. It is important to ensure that any water delivered to the plants does not leak onto flooring or come into contact with walls, as this can lead to the growth of fungus and similar undesirables. Proper water collection and drainage is important for both indoor and outdoor living walls.
While living walls do promote a healthy biodiversity, it is an indiscriminate promotion and can lead to the presence of unwanted organisms. For this reason it is best to occasionally check the living wall for the presence of unwanted insects and to deal with them immediately if discovered. On outdoor living walls, this can even be done with the introduction of helpful insects such as ladybugs.
Button Drippers
One of the most common ways to irrigate a living wall is by simply using punched in button drippers. Button drippers are also very common on outside drip irrigation systems; from residential gardens and raised beds to expansive vineyards covering acres, button drippers have proven to be efficient, reliable and durable.
This method consists of simply running your ½” or larger tubing up one side of the living wall and across the top. For walls with multiple levels, tubing Tees can be used on the vertical climb to create additional horizontal tubing runs. Tubing can be secured to the wall in a variety of ways depending on the material of the wall. Trellis wire and support hooks, clamps with a nail hammered into the structure of the wall; even zip ties can be placed and used discreetly.
Button drippers can be punched directly into the horizontal tubing runs to drip on the plants below. This method is both simple and economical. The drippers used most frequently are 0.5 GPH drippers, but this can vary by plant and substrate type, with thirstier plants and looser soil types opt for higher flow rate drippers. It’s not uncommon to use pressure compensating drippers to prevent drippers on lower rows from draining after system shut-off.
Some living wall types are made of material with strong capillary action, or “wicking action.” This means that some of the water will make its way down through the material and to the bottom plants. In most cases this will not present a problem at all; the drainage of the bottom plants will see excess water drained into a drainage tray or other item designed to reclaim the water. In other cases, we often see the thirstiest plants placed on the bottom rows, and/or higher flow emitters used at the top than at the bottom so that less water is drained into the tray below.
It’s easy to overthink this part, so consider it like this: water that the soil or material cannot absorb and hold, will be drained to the next level. When that level’s infiltration rate is reached, excess water will drain to the next, and so on. What this means is that the plants will essentially get approximately the same amount of water either way, and the big question is how to handle the water that drains below the bottom level. Reclaiming that water for use is common, with some systems even re-circulating it back through on the next cycle. Those types of systems often use a small pump and water tank to move the water through the tubing and out the emitters.
Below is an illustration that shows how one of these systems may look. As you can see, due to the modularity of the components, it would be easy to scale this type of system to living walls of various sizes and material types, even up to some of the very large sizes seen on commercial projects.
For smaller living walls, ¼” poly tubing with inline drippers can be used. These types of systems are very similar to the one above, but instead of button drippers punched directly into ½” or larger tubing, they feature ¼” poly tubing connected to inline dippers above the plants. Inline drippers feature two barbs that allows both ends to be connected to poly tubing, thus the the ¼” run can continue after connecting a dripper. These emit water from an outlet on the flat disc between the two barbs.
One advantage to this design is that each pocket has its own on/off. This can be handy if the plants in one pocket require less water than those in the other pockets. The individual on/off comes from the ¼” coupling valves you see in the graphic above. A ¼” coupling valve serves as both a coupling, to join two pieces of tubing together, and as an on/off valve to control the flow of downstream water. The ¼” tubing should be limited to 30’ in length and 30 GPH in flow, something to keep in mind depending on the size of your living wall.
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