Lighting Guide for Vertical Gardens
by Chris Bribach
Plants Need Light
Natural light outdoors is the ideal source for growing plants.
Daylight produces 10,000 foot candles of light. This is perfect for herbs, vegetables, grasses, succulents and many other plants that thrive in full sun or even part shade.
For indoors we select low light tropical plants that are native to the forest floor beneath the tree canopy receiving 250 foot candles and temperatures around 70 degrees. These conditions are typical to our interior spaces. What we consider 'house plants' are suitable to our optimal living conditions as well.
Low light tropical plants typically like bright indirect light however too much light or direct sun will burn their foliage. In places where there is not quite enough light supplemental lighting will be required.
Choosing the right plants for your location is very important.
See Choosing Plants
Free Light Energy From The Sun
Ideal lighting would come from a skylight above or window across from the vertical garden. It costs nothing and is the most ecological solution. Diffused light near a large window becomes ideal conditions for low light tropical plants.
It may be that a beam of light passes over the vertical garden for a couple of hours each day.
Know your Light
Get A Light Meter
To determine light levels get a light meter. Light levels are measured in Foot Candles. Low light tropical plants will survive with 150 - 250 foot candles of lighting and will need 8-10 hours each day.
Hydrofarm Digital Light Meter - About $40
The Color of Light
Choosing the color mostly affects how we will view the plants. Warmer colors recreate summer light that encourages blooming. Bluer light will help plants develop their foliage. Vertical gardens are typically for enjoying their beauty therefore 4000K is a balanced warm daylight that looks best with plants.
Halogen spot and flood bulbs project light to the plants. Track lighting systems are low cost and easy to install.
Halogen creates a very broad spectrum of light and delivers the most attractive full balanced color making plants look their best. Also they create some warmth that is beneficial for most low light tropical plants.
Costly to Operate
The downside is that they are not as efficient at producing light as other sources. Operational cost and ecological impact goes up. Therefore these are best to use for smaller projects or in areas where beauty is most important.
Efficiency in Lumens per Watt
Halogen - 25 Lumens per Watt
Metal Halide - 100 Lumens per Watt
LED Lighting - 100 Lumens per Watt
Recirc Interior Lighting Guide
Metal Halide Lighting
A Full Spectrum
Metal Halide creates full spectrum lighting best for plants
- UV component
- Best watt to lumen (foot candle) efficiency
Plants Need Ultraviolet Light
Evolved to Love the Sun
Plants have evolved in nature to optimize their photosynthesis at the ends of the spectrum.
In plants, Ultraviolet (UV) blue light are required for green vegetative growth while red wavelengths aid in their flowering and fruiting phases.
For vertical gardens it is desirable to provide plants with a wide spectrum of light so we can also enjoy the visible beauty of plants.
A Metal Halide spectrum better mimics sunlight and provides full spectrum for chlorophyll function at 450 nm and 500 nm areas and in the 640 nm and 650 nm wavelengths.
GE Ceramic Metal Halide Bulb - 4200K
The spectral power distribution diagram of the above bulb shows an even distribution of power in the peak chlorophyll production zones. It also includes a nice balance of the central visible spectrums that also deliver pleasant viewing.
Our test gardens have shown that Halogens do provide adequate light to keep low-light tropical plants alive. Whereas our Metal Halide test gardens show more aggressive growth in bright light loving plants such as ferns.
Metal Halide Indoors
Nuvo Lighting Metal Halide Track Head Black 1 T439W/MH/G12 Base, Black, TH382
Houzz about $65 > Buy Online
High quality compact interior fixture. About $160.
Produces about 600 foot candles at 4 feet for each fixture with a spread of about 3 feet diameter and about 150 foot candles at 8 feet with a 2 foot diameter.
Note the bulb must also be purchased, below.
Easy Metal Halide Lighting
A simple track lighting system can be purchased online to create a simple plug-in system. We've created a link page where you can get the parts for an 8' wide track system with timer. This will produce 300 foot candles of energy efficient full spectrum lighting for a 20 square foot tall vertical garden.
Recessed Metal Halide Fixture
Recessed fixtures are available for a more finished look for architectural application.
Metal Halide Outdoors
Metal Halide Spot Fixture
Metal halide requires a transformer and ballast to ignite the gas in the bulb. These parts are inside it's fairly large base. Note the bulb socket may look like a regular type, but these are for metal halide bulbs only.
To distribute enough light over a wall surface you will need a fixture for each 10 square feet. This fixture will deliver about 300 foot candles to an area about 3' x 3'. If the fixture is far away 10' or more you will need to use a spot to project the light energy to the wall. If closer you can use a flood to distribute the light more evenly.
How many watts should I use?
Rule of thumb for most low light tropicals and most ferns:
- 10 Watts per Square foot makes about 400 foot candles.
- A 20 square foot wall would need 200 watts.
- Use 5 of the 39-watt track light fixtures.
- It's always a good idea to round up.
- Use spot bulbs to focus all of the light energy on the wall.
The Future of LED Lighting
Are LED Lights good for growing plants?
LED lights hold promise for becoming the best solution for lighting vertical gardens. But currently there are some limitations.
- A spiked spectrum leaves out wavelengths.
- Available bulbs are designed for residential use and remove UV to prevent fading of art and furniture.
- Lights for growers are offered in a pink color to optimize the usable spectrums, but offer a very unattractive light.
- New CREE type bulbs offer promise but are not offered in spot type fixtures that project light energy efficiently.
- More testing of CREE needs to be done to know if it will in fact grow a wide variety of plants with excellent results.
- LEDs are very expensive.
Share Your Findings
As we learn more we will update our findings with regards to LED lighting as a practical solution for vertical gardens and living walls. Metal Halide are currently the most viable option.
We are always learning. Let us know your experience.