Understanding Greenhouse Lighting

May 24, 2018   

There’s a lot more to greenhouse lighting than meets the eye. Growers in search of the appropriate lighting for their greenhouse should consider the following three factors: the type of crop being grown, what time of year it is and how much sunlight is available.

Greenhouses generally require six hours of direct or full spectrum light each day. If this can’t be done naturally, supplemental lighting must be incorporated. Supplemental lighting is the use of multiple, high-intensity artificial lights to promote crop growth and yield. Hobbyists like to use them to maintain growth and extend the grow season, whereas commercial growers use them to boost yields and profits.

Equally important as supplemental lighting is photoperiod control lighting. A photoperiod of light is the number of hours that a plant receives light in a 24 hour time span. For example, if the sun rises at 6 in the morning and sets at 8 in the evening, a 14 hour photoperiod has lapsed. Photoperiod control lights are used to simulate long days, triggering early flowering or promoting delayed flowering, depending on the plant’s needs.

Growers have a wide array of lighting options to pick from, so it’s important to understand the nuances of differing lighting styles. Let’s examine the uses and advantages of four different lighting types.  

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High Pressure Sodium Fixtures

High pressure sodium fixtures provide more orange and red spectrum light and have a golden-white appearance to the human eye. Since they promote budding and flowering, they are generally used later in the growth cycle of the plant. These fixtures are approximately 7 times more efficient than incandescent bulbs and work best when used in conjunction with natural daylight, making them a great option for greenhouses.  High pressure sodium lights also offer the potential for a 10% increase in intensity and photosynthetically active radiation (PAR.)

Give high pressure sodium lights about 4 to 5 minutes to warm up and one minute to cool down. It is for this reason that they aren’t good for locations where the lights turn on and off frequently. It’s also important to be cognizant of placement; high pressure sodium lights should be mounted 30 to 36 inches above the plant for optimal results.

Fixed and Programmable Spectrum LED Fixtures

LED (light emitting diode) fixtures are the longest lasting option offered by Growers Supply, with a typical lifespan of 50,000 hours. The diode of an LED won’t burn out as fast as standard light bulbs, which gives it such an incredibly long lifespan. LED lighting fixtures have a higher efficiency than standard lighting because more of the power input goes to light than heat.  For instance, incandescent bulbs are only about 20% efficient, as most of their input power goes to producing heat.

Perhaps one of the biggest advantages of LED lighting is the massive energy savings. They are easily integrated into any operation and offer up to 70% savings when compared to high-intensity discharge (HID) lighting.

There is no warm-up time required with an LED fixture and they are also free of mercury, making disposal much easier than other bulbs. LED’s provide superior functionality when used as a sole source of lighting, making them an attractive option for many growers.

Ceramic Metal Halide

Ceramic metal halide lamps are used for their blue light, although they appear bright-white to the human eye. They can easily function as a primary light source, with an average lifespan between 8,000 to 15,000 hours. Since metal halides are 3 to 5 times more efficient than incandescent bulbs, they make an excellent option for areas that don’t receive natural sun.  

Important to note is that metal halides have to warm up for about 5 minutes or less before they can give out full light. They also need a cool down period of about 5 to 10 minutes before restarting. For this reason, they are not recommended for locations where the lights will turn on and off frequently.

Ceramic metal halide lights should be hung 30 to 36 inches over plants and can result in darkened leaves and overall healthy-looking greenery. Growers Supply PARLucent Ceramic Metal Halide Lights are ideal for greenhouse and hydroponic applications. Growers often use them in the early phase of a plant’s life when seeds are in the vegetative growth phase. The dimmable ballast allows growers to obtain the perfect lighting for their operation. They are completely silent too, so there are no bothersome humming, buzzing or high-pitched noises to deal with.

T5 Fixtures

T5 fixtures are the most efficient and most popular fluorescent greenhouse lighting option for growing. They use less energy than traditional lamps and can last up to 50,000 hours. These environmentally-friendly lights sometimes feature aluminum reflectors for maximum efficiency. They are ideal for use in hydroponics, greenhouses, warehouses, barns and more. They can be used from the initial phase of seed starting to full term growth.

The letter “T” denotes the tubular shape of the lamp and the number 5 indicates its diameter in eighths of an inch. T5 lamps are slim, only 5/8” of an inch in diameter, which makes T5 fluorescent tubes more efficient than standard fluorescent tubes.

GrowSpan’s High-Performance 45” T5 Fluorescent Lamp features extremely high lumen output and full spectrum lighting that is excellent for plants from the seedling stage up to full term growth. Its minimal heat output means that it can safely be placed very close to plants, within 6 to 12 inches to be precise. While there’s technically no such thing as too much light, it’s important not to use too powerful a light in a small space, which can result in overheating of the leaf surface area.

With so many greenhouse lighting options tailored to different plant types and stages of growth, it’s easy to see why expert guidance is so valued by growers everywhere. When working with GrowSpan, growers have access to custom lighting plans, automated and computer controlled lighting and even Greenhouse Specialists that provide professional lighting design. GrowSpan’s wide range of lighting solutions, from supplemental growth to photoperiod control, make optimizing a grow space a simple, efficient process.

To speak to a lighting specialist Request a Quote here. To get a Greenhouse Quote, click here.