High-Pressure Sodium. (HPS) light puts off an orange: shaded light which simulates the rich red hue of the autumn sun. Best as fruiting or flowering. lights, the HPS systems are often used In conjunction with metal halide for a complete balance of light spectrum in the garden. Flowers and vegetables finished off under HPS will show tighter, stouter blossoms with increased yields.
HPS lights are commonly used in commercial greenhouses as starting lights and for supplemental light for off-season crops. Some types of plants respond particularly well to HPS lighting, such as the herbs dill and coriander.
As stated earlier, High Pressure Sodium lights emit mainly in the red to orange part of the visible light spectrum. This part of the spectrum is particularly good for the flowering and fruiting portion of a plants life, using HPS lights at this stage can increase yields significantly. HPS lighting during the vegetative stages of growth, however, can cause plants to grow tall and spindly which does not make for a strong plant.
Many hydroponic gardeners do prefer sodium lamps to metal halide because sodium lights are more energy efficient and often last longer. They also produce large crops of quality fruits, vegetables and herbs, when employed at the flowering and fruiting stages. HPS lights are more intense than MH lights, producing more lumens per watt than MH lights.
HPS lights produce a lot of heat. This heat may need to be vented or dissipated if your growing space may become too hot. It is important to make this decision before you buy your light fixture, so that if necessary you can purchase a hood that is set up to accept ducting.
Some positive attributes of HPS lighting:
- More energy efficient than MH bulbs
- Bulbs last longer than MH bulbs
- Great for flowering and fruiting stages
- More lumens per watt than MH bulbs
And a few negative attributes:
- Produce a lot of heat
- Not as good for vegetative stages of plant growth