Function

• Optimum development in plants requires blue and/or red light. Blue light encourages compact growth, while red light is necessary to start the blooming process.
  
  

Considerations

• Cost, floor space, electricity usage, and accessibility to replacement parts must be taken into account when using grow lights.
  
  

Types

• Grow lights fall into three categories: fluorescents, which are most popular among home gardeners; high intensity discharge, which includes metal halides and high pressure sodiums; and light emitting diodes (LEDs).
  
  

Features

• Readily available fluorescents are inexpensive and energy efficient; high output fluorescents are fairly thin. Metal halides mimic sunlight, producing compact plants resembling those grown outdoors. High pressure sodiums encourage blossom production. Lightweight LEDs are extremely energy efficient.
  
  

Disadvantages

• Fluorescents requiring a ballast are heavy, needing secure installation. Bulb lifespan is 20,000 hours but subject to cathode decay. Costly additional equipment makes HIDs better suited for commercial growers. LED effectiveness research is ongoing.
  
  

Caution

• Incandescent lights, such as light bulbs, should never be used as grow lights. Heat produced by the bulbs can burn plants and create a fire safety hazard.