Green Wall Lighting in Australia: A Take from a Lighting Manufacturer

Hi Zack, can you please tell us about yourself and your work in the lighting industry and at Unios?

I’ve worked in the electrical and lighting industry since I was 10 years old, helping my dad to earn some pocket money. I, then, went on to complete my electrical apprenticeship before pivoting into residential lighting design. As for Unios, I’ve been with the business since infancy. It has gone way too quickly! I’ve worked for Unios, in some way or another, in every state of Australia and New Zealand, having the absolute pleasure of meeting some incredibly talented individuals in the design community along the way. I currently work as the Product Lead, helping combine my knowledge of the industry and our amazing supporters to create exciting new products.

Having led numerous biophilic/green design and horticultural lighting campaigns at Unios, how do you define horticultural and green wall lighting?

Horticulture lighting is the method for stimulating plant growth with artificial lighting fixtures in an indoor setting or when natural light is lacking. On the other hand, green wall lighting, in short, is the lighting system for different types of plants or other greenery attached on walls or other vertical structures.

From my experience, LED lighting systems have several effects on existing horticulture, especially the lifecycle and quality of greenery. However, these benefits can only be realised with long-term research and deep testing of LED lighting’s advantages and disadvantages on plants, people and the surrounding environment.

So Zack, let’s start with your role as the manufacturer in the green lighting industry. How did you become interested in green and horticultural lighting? When asked to provide a “green wall lighting solution” without having additional project-specific information, what approach do you take, and how do you determine the best possible light source for the plants and visual solution for humans?

My interest in and knowledge of Biophilic/Green lighting design started around six years ago when we started to investigate introducing the Flo Technology to the ANZ market. I had the opportunity to be educated on the intricacies of lighting for plants from global LED brands like Citizen, Samsung and Xicato, and from there have met with many wonderful people along the way. I’ve thoroughly enjoyed working with botanists, horticulturalists and lighting designers to understand more about the complexities of lighting for plants. It’s such an interesting space.

Providing a solution is tricky! The landscape we are in (pun intended) is hard to navigate sometimes. Yes, we are the manufacturers, so we try our best to inform, discuss and educate the designers. The hope is this will assist them in providing the right solution. That said, we have little control over the outcome. Most of the time, we need more understanding of the project and installation regarding light levels, layout, and plant selection. All in all, it can be a bit of a struggle.

With that reality in mind, the industry, from the manufacturer to specifiers, tends to try and find a law of averages to apply across a broad scope of projects. So, to answer your question, when I’m asked to provide a “green wall lighting solution” without having additional project-specific information, I usually offer a white light source with the highest possible Gamut and Fidelity — determined using TM30-15, rather than CRI as it’s not an accurate indicator of the colour spectrum being produced by the LED White Light source. This way, I know most wavelengths are being covered and to a high level. As a generalisation, I know most “tropical” foliage used on interior walls requires roughly 45µmol/s/m², which you can think of as the amount of light, with a specific photosynthetic spectrum, landing on the plants, per second, per square metre. This is usually achieved by a specialised fitting, between 3,000-6,000 Kelvin and 2,500-10,000 Lux.

However, providing this as a solution is like suggesting a pair of shoes without ever knowing the foot size. A generic size 12 would cover most bases. The shoe would be wearable but never a perfect fit, and in this case, the generic size 12 for green wall lighting would be High Output, 3500K, CRI95+ Rf90+ Rg90+ This should cover the minimum requirements for the tropical plants, and provide the best visual solution from a human perspective.

Five years ago, Unios released its first horticulture lighting product, the Flo Series. Knowing what you know now, what’s your take on this product range as a green wall solution?

The Flo Series entered the market as our first attempt at a self-confessed “one size, fits all” or “size 12” product. With this range, we tried to produce a fitting that could do everything, from lighting green walls, vertical gardens, and indoor trees to complex internal garden spaces. Of course, we have faced some fair criticism for this.

With much ambition, we adopted Citizen technology. At the time, our focus wasn’t only on vertical green walls. Some of our early concepts and designs were on large indoor gardens and intricate internal garden spaces. However, most of the market is vertical green walls, and the range often catches people off guard with the pinkish hue that the COB delivers. For insight, Citizen manufactured this light source to produce only red and blue wavelengths, which might be strange to the usual aesthetic of architectural lighting, but an absolute treat for plants, as it targeted specific pigments in the plants, known as Chlorophyll. These types of solutions are quite popular for indoor farming and horticulture because most plant species depend mainly on these wavelengths as a part of photosynthesis. Therefore, the Flo Series is the ideal solution for projects requiring high levels of growth rather than maintenance.

Having said that, the Flo can be a valuable solution for green wall projects because it produces higher levels of PPFD (Photosynthetic Photon Flux Density) than white light LED sources alone. However, we commonly present the benefits of colour mixing, which aligns with the technical requirements for plant growth and the need for visual and architectural aesthetics. Colour mixing is when the Flo is positioned alongside a 4000K or 3000K light source to wash out some of the pinkish hues reflecting on the interior elements and being read by the eye.

The issue is that the budgets often do not allow a properly mixed design, and we sometimes aren’t fully engaged to make sure the design is done correctly, or we commonly don’t have the data requirements from all parties. At this point, I’m happy to admit the Flo could be revisited and re-engineered to be green-wall focused. But, to make it clear, regardless of the fitting or brand, there isn’t a horticultural lighting solution that suits all. The only one available is the sun, which we cannot produce artificially with the current age of technology.

As an industry, it seems that we are still relatively far from being able to create lighting conditions perfect for our green pals since there are so many variables at play. So, diving deeper into that, what are the hurdles for green wall lighting?

The fact that every project is different is a hurdle. Of course, I don’t hope all projects will be the same. Different projects mean more learning opportunities, but it’s a challenge to cater to the varying requirements. I’ve worked on concepts for Apple Trees, Olive Trees, scattered Pot Plants, internal office herb gardens, and large indoor botanical gardens, along with plenty of green walls.

One of my biggest bug bearers is that even though the projects vary significantly, the market expects a “size 12” solution with green walls and everything biophilic and green design. And that does not exist. A lighting solution that maintains Sword Fern won’t grow and sustain an Apple Tree. After all, we are discussing providing food and sustenance to living organisms. Two living things are never the same, and neither are their environments. A comparison could be made that if all humans eat ten potatoes a day, we’ll all live happily ever after, which isn’t true. Likewise, to say that all plants need a minimum of “X” Lux levels at “Y “colour temperature for however many hours is incorrect. Each species is different, and thus their installation and environment should vary. So, can we concur with these variables to support indoor greenery? Well, this leads me to the most critical challenge: insufficient data.

Sadly for all our potted green pals, we don’t know the exact number of micromoles required for each species’ needs. Which, when designing intricate and beautiful walls, means we can be over or underfeeding the foliage, and when it comes to internal trees, it’s really a stab in the dark, if we cannot find specialists. There are also no standards regarding the right amount of PPF-D, mainly because most investigative papers focus on vegetative plants or marijuana. Due to the lack of data on micromuls requirements, green wall suppliers, lighting designers, architects, engineers and horticulturalists seek to determine and design based on the averages to cover a broad spectrum.

The thing is, even these averages and ideals are different. Some out there strongly suggest a certain small window of CCT, which is counter-intuitive if we consider that Correlated Colour Temperature is a reference measure to white light, perceptible to the human eye. Plants aren’t humans; they use light differently, and most use more range than we can visualise. The same argument can be said for those stipulating a high CRI; again, this is subjective and calculated as an average. These measurements are commonly used because we currently look to white light LEDs for indoor spaces due to aesthetics requirements.

I think these misunderstandings lead us to the averages and so-called best practices you see out there. In reality, each and every installation is different from one another. For example, is there access to daylight, is there a lot of daylight, some daylight, or is there only daylight for certain hours in the day. The plants can also be affected by other artificial lights in the space, like the light levels from those. Then, what plant species are going in, in what arrangement, are there overlapping large leaves, where can the lights be mounted, what is the architecture like, and who is in charge of commissioning the lighting to achieve the design intent. These are all things that can be overlooked, if we simply state a minimum Lux level target for a flat wall surface.

I thought it would also be good to turn to a friend in the industry for his comments. Erik van Zuilekom, from Fytogreen, specialises in green wall design and research, with 15 years of experience designing long-term successful, sustainable, resilient and dynamic/adaptive vertical gardens and 27 years of experience conducting botanical and ecological research into plants and habitats suitable for use in living architecture technologies.

From a designer’s perspective, Erik mentioned that most horticulturists need to recognise the degree of extremely low light most vertical garden installations are provided. The horticultural, agricultural and design industries require an expansion in our lighting, sun and shade vernacular to aid us in better understanding and teaching the highly varied lighting requirements for plants. For example, the full sun in Australia is typically about 100,000 Lux. With dappled shade below a half-density tree canopy equating to the half-light of circa 50,000 Lux, a quarter-deep shade of 25,000 Lux. Simultaneously, a very deep shade of circa 12,500 Lux and an extremely deep shade below 6000 Lux. Yet, most vertical gardens fall into a parameter of 3000 Lux and below.

Erik also agrees that Lux is a very limited concept to define plant lighting requirements. It’s the first factor of many that comprise the range of inputs impacting what plants require, such as light intensity, quality and duration of exposure. For this reason, PPFD becomes more valuable as it includes intensity, quality and duration of exposure. Yet, it doesn’t define how this can be achieved on a sliding scale of the mentioned factors, each impacting how plants grow. Achieving a target PPFD may still result in poor performance for certain species requiring a higher percentage of particular light wavelengths (light quality), whilst others may struggle under a particular daily duration of exposure. Likewise, varying light quality and time may require higher intensities to meet the same PPFD target, potentially leading to foliage scorch for deep-shade-tolerant species.

It sounds like there needs to be some in-depth research done. So from a lighting perspective, what happens if these things aren’t properly considered or overlooked for whatever reason?

Well, the responsibility is unclear. I heard of a project in Sydney where a cleaner had accidentally sprayed some of the plants with window cleaner, not realising it filtered through the water system and eventually killed the plants. The matter of whose job it is to keep these plants alive is in a grey area, and so is the responsibility of the plants dying. Is it the designer, manufacturer, installer, or occupant?

There are great companies like Fytogreen that offer incredibly sustainable designs and set out to achieve permanent plantings, reducing the need for replanting or routine replacements. However, many don’t have the same aim, so it is super important that we encourage the end client and/or developers to consider all the parameters and speak to the right businesses.

Otherwise, this leads to another pain point: the unsustainable, fast-fashion approach to maintaining green walls and indoor greenery. I’ve been to these projects in the past, where the artificial lighting for the space has been positioned to light a range of foliage under suppliers’ guidance. But instead of promoting growth, the intensity burned and destroyed the vegetation. The impact of this continual replacement has some yet-to-be-fully understood effects on our environment.

Don’t get me wrong, indoor plants and green walls are fantastic and offer a range of benefits, but the recent craze may have uncovered some serious issues regarding plant poaching and maybe global warming. So as an industry, we need to install foliage that can be maintained rather than constantly replaced.

Okay, so five years is a long time. Have some things changed that could help develop lighting technology for plants?

From a lighting manufacturer’s point of view, most discoveries have come from the investment into horticultural lighting for medicinal marijuana since this has far more funding than green or biophilic design. The most applicable discovery is regarding plant light absorbance within photosynthetic active radiation. Or, in layman’s terms, which parts of the light spectrum are usable for plants.

The big one is that there’s more to it than just Chlorophyll. Although most brands I’ve encountered talk mainly about Chlorophyll A vs B, there is far more to it. To explain, Chlorophyll helps plants create their food through photosynthesis. It’s a pigment in plants that helps to give them a green colour. Most brands, like Unios, talk about targeting these pigments to sustain and grow plants. But it’s become apparent that we are missing out on some key ingredients:

Learning 1: Cryptochromes, Photropins and Phytochrome Red.

Cryptochromes come from a Greek word meaning “Hidden Colour” because the proteins found in plants and animals are susceptible to blue light and are heavily involved in plants’ circadian rhythms. Plant circadian rhythms tell the plant what season it is and when to flower for the best chance of attracting pollinators. They also assist the plant’s direction of growth and are part of the reason behind, why plants tend to grow towards a light source.

Phytotropins are responsible for plant stem growth. So, it could be essential for some installations to target stem growth. Phytotropins are also highly reactive to blue light and have been linked to helping the spread of chloroplasts, which are essential to plant health.

Photochrome Red reacts to the Red and Far-Red spectrum. These cells are essential for the plant’s architecture. It is mainly responsible for the size and shape of the leaves and flowering of particular foliage.

It’s important to note that most of these tend to tread toward the UV or Infrared Spectrum of Light, which can pose health risks to us as humans. As discussed by Jerry Plank for IES Safety: Assessing Horticultural Lighting. I’m not suggesting we build vertical solariums to maintain plant life, but that we consider more of the process in which plants and foliage use light. There are always solutions around these things; if we’ve become so developed as cities that we need to depend on internal gardens, we could look to provide the 12-hour full light spectrum at night. After all, interior plants without sunlight don’t follow our day-night cycle.

Learning 2: Green light and its effect on light absorption for stability.

For a long time, green wavelengths of light, specifically 480-510nm, have often been considered a wasted light spectrum for plants. This is because they play less of a role in photosynthesis. However, recent studies show that green light can assist with light absorption. In addition, green light is more transitive, penetrating the plant canopy deeper, helping carry light to foliage covered by large leaf plants. So that it can still photosynthesise and grow. Additionally, green light is linked to plant stability rather than growth. So in the case of a green wall, which is usually planted at full growth

Finally, before wrapping up this article, is there a message you want our audience to take away from your interview?

Something I would like to stress on is to rely on brands that promote and manufacture the fittings. Although I understand design professionals need to retain integrity and anonymity when designing the lighting solution for these projects, manufacturers are here to help produce the best solution for projects.

Also, work with credible botanists and horticulturalists who can produce a sustainable green solution where possible. There are great, credible brands with a wealth of knowledge, so seek guidance, ask questions and encourage debate. That way, we can all build a greater understanding, leading to greater and more sustainable adoption of vertical gardens, green walls and even things like internal parks and indoor forests.