Dark Sky

Landscape Lighting - Illuminating gardens at night, good neighbor lighting, light trespass, night lighting levels and color temperature.

Learning Objectives - Landscape Lighting

Why is dim lighting important in gardens?
How is landscape lighting like theatrical lighting?
What is good neighbor lighting?
Why shine the light down?

Tips for Landscape Lighting

Outdoor lighting, any lighting, benefits from understanding theatrical lighting. Having a single dim light behind a window creates mystery on stage, what will happen next? Sometimes on stage, and often outdoors, a little light goes a long way.

Pick a few plants to light near, back, and far. This will create depth, just like using low, middle, and tall plants in your perennial border. With light you create a visual destination in the background that will show the depth and scale of the garden. Keep it subtle, you want to make a suggestion of light rather than a focus. It takes up to 20 minutes for your eyes to adjust to dim lighting, if it is too bright, you will never see the non-illuminated parts of the garden. If it is dim, as your eyes adjust, the tree you feature in the background will be revealed.

Photo by Trish Odenthal

It is easy to overdo it with outdoor lighting. As in interiors, you want ‘layers of light’ with opportunities to have different combinations of lights on and off.

Grey foliage and white flowers are easiest to light at night. Look at what shows up in your garden under the full moon, Red flowers disappear, while white ones glow nicely.

Moon Lighting

Shine lights down whenever possible. ‘Moonlights’ are designed to hang from tree branches and simulate the moon light falling onto the path or plants below. Try to avoid the ones with tiny holes drilled into the sides, since they create ‘daggers of light’ that can be blinding. Plus the glowing holes give away the secret light locations, dampening the mystery of hidden lighting.

Lighting Trees

Uplighting into tree branches is tricky. You need a canopy of leaves or branches and tree trunk to catch the light and reflect it back, since we cannot see the light until it strikes a surface and bounces back to your eye. Sometimes leaves will be translucent and glow softly for a nice effect, experiment with a flashlight to predict your results.

Trunks and branches can be illuminated with spotlights from the ground; however, this creates wasted light shining into the sky and prevents stargazing. Carefully select which trees and where to put your lights. Deciduous trees and large trees have interesting branches and bark. To show off the texture of the bark, you want ‘grazing’ light, that hits the bark at a sharp angle to create shadows and highlight the texture. If you are lighting from the ground, place fixtures so that the light grazes the branches. For a huge specimen you can use three floodlights from the ground, for giant oaks at a wedding venue I have used five. This is where your theatrical lighting comes in. You want variety of angles and beam spreads, spot for intense focus and brilliance on one side of the trunk (key light), medium beam for balance coming from the other side to show the trunk or branch is round (fill light), and wide beam or flood from behind into the canopy for depth and background (back light).

Outdoor Dining

Photo by Trish Odenthal

Many people like twinkle lights for outdoor dining.

Avoid overly bright lights, more wattage and lumens are not your friend.
Buy WARM lights that look yellow (2700 Kelvin) instead of blue (4000 Kelvin), we are trying to simulate candle light on people’s faces.
Find lights that are frosted not clear, clear is too glary and makes harsh shadows.
Look for lights with a canopy or tiny hat, or some diffuser to soften the light.
If you want to dim them, look for a compatible LED light source and dimmer, if they are not designed to go together, you may get a lot of flicker or on/off without dimming.

Lighting Steps & Stairs

When lighting steps and stairs the goal is to alert guests to changes in height, direction, and texture. These changes are surprises that in the dark become tripping hazards.
A rule of thumb for stairs is to light the top, bottom, and in between on long runs.

Color Temperature of Landscape Lights

Consider what you are lighting when selecting color temperature. You can buy lights that look golden yellow or blue white. It is hard to find ones in the neutral white range for outdoors.
For lighting near people, use WARM lights that look yellow (2700 Kelvin) instead of COOL blue (4000 Kelvin).
Use cool blue lights when you want foliage to look green, the warm lights can turn a nice green bush into a brown blob.
Most outdoor lighting does not have CRI (Color Rendering Index) but if yours does, you want the 90+ not the 70 CRI. The lower the number, the bigger the gaps between wavelengths of the color spectrum causing color biased lighting. The 90+ will cost a little more and be a little less bright, worth the trade off for quality light.

Low Voltage Wiring

Most outdoor landscape lighting is ‘low voltage’ meaning the standard 120 volt power has been modified to 12 or 24 volts. You can ask your electrician leave ‘long leads’ of coiled extra wire, so you can move and adjust the lights before the final installation is finished.

You will probably have a ‘transformer’ installed in a shed, garage, side of a building, or underground weatherproof box, to convert the 120 volt to 12 volt before it is distributed into the garden. Today, some companies, have individually addressable fixtures, so that you can dim, turn on or off, and adjust the color of each fixture separately, even though they are on the same power supply. This type of system is useful in large public gardens; however, may be too pricey and unnecessary for a residence.

Good Neighbor Lighting

Be thoughtful to neighbors, by only having the lights on when you are viewing or entertaining. Consider light trespass and direct glare (seeing the bulb) from your neighbors point of view. Shield all light sources from view for your own and neighbor's visual comfort. Preserve the dark sky - at night, put light where it is needed, keep it warm, keep it dim. Light Pollution, Light Trespass, Night Lighting Levels and Color Temperature, Sources, Astronomy, Dark Sky, Circadian System

What is Light Pollution?

The inappropriate or excessive use of artificial light – known as light pollution – can have serious environmental consequences for humans, wildlife, and our climate. Components of light pollution include:

Glare – excessive brightness that causes visual discomfort
Skyglow – brightening of the night sky over inhabited areas
Light trespass – light falling where it is not intended or needed
Clutter – bright, confusing and excessive groupings of light sources

Local Outdoor Lighting Ordinances

Many cities and counties have an outdoor lighting ordinance restricting lighting levels, duration, and color temperature. Check with your jurisdiction about regulations before investing in your outdoor landscape lighting system. See Dark Sky & Ordinances page.

Dark Sky Lighting Fixtures

Luminaire Shielding Designs Image courtesy of Bob Crelin

What is a Dark Sky Light Fixture?
The goal is to avoid sending light into the sky; therefore, we call it 'dark sky.' The specifics vary according to jurisdiction. There are some basics qualities of dark sky lighting that seem universal. All light should be below the fixture, the light should be aimed down. International Dark Sky Organization has a listing of Dark Sky Certified fixtures. www.darksky.org Find your nearest chapter and learn more.

Outdoor Lighting Manufacturers & Materials

There are many outdoor lighting manufacturers, if you want your equipment to last 20 years, many good companies make high quality equipment, look at warranty details, five years is a good warranty, although they should last much longer. If you are experimenting and are happy with 2 or 10 years, go with a less expensive brand.

Finish - the finish is one of the biggest challenges with outdoor lighting equipment, near the ocean even more difficult. Rust is a type of patina that forms the familiar red orange gritty surface on steel, eventually rusting through reducing the strength, other metals will patina by chalking or changing color.

Stainless Steel - there are various grades of stainless steel, most manufactures do not list the rating, many inexpensive stainless steel fixtures will rust in the first year. Lighting fixtures are not made of the same alloys as those for surgical, nautical, and cutlery applications. See more info on Wiki.
Powder Coated Paint - this finish is applied electrostatically to steel or aluminum and is then cured under heat. Eventually the finish will become chalky, a process delayed if you consistently apply car wax.
Paint - paint on metal is an economical solution that may become chalky or rusty over time.
Natural Metal - Brass and Copper will naturally patina with age, changing color to something between a dirty penny and bright green, depending on salt and humidity in the air. A clear coat is applied to some fixtures to preserve the bright shiny finish and some manufacturers offer accelerated aged finish such as aged bronze.
Galvanized Steel - a process of applying a thick metal coating of zinc to the metal, making it weather proof, eventually it may corrode, often seen on pipe fittings.
Aluminum - the patina that forms on aluminum is a chalky residue that cannot be washed off, a clear coat is recommended. Anodized aluminum finish may change over time with exposure to the elements, sealing will improve corrosion resistance.
Keep any rubber washers in place to prevent accelerated corrosion with disparate metals and use care and research when joining metal parts. Corrosion progressively destroys the metal, causing weakness, which can lead to failure. Use the corrosion potential chart when selecting fastener/bolt material. Remember to never use materials far apart (i.e., never use a fastener made of brass or copper to fasten aluminum and steel. (1)

Solar Powered LED Path Lights

Due to their low price point, small solar LED pathlights are usually too glary and don’t spread the light very far, this is why you see people place them two or three feet apart.
Some solar powered flood lights may work for your trees; however, you cannot turn them on and off very easily. You have to traipse into the garden to find the switch on the fixture or wait for the battery dying to turn them off.

Footnotes

1. www.trailer-bodybuilders.com/fabrication/how-deal-dissimilar-metals

Photo Credits

Unless noted, all photos on this page courtesy of BK Lighting

Landscape Lighting