Long-day plants are induced to flower earlier and continue to put on vegetative growth. Day-neutral plants continue to grow vegetatively. A concern with landscape lighting is that plants will continue vegetative growth late in the season. This late growth will not have the opportunity to harden off properly before winter and may experience severe winter injury. The most common types of lighting include incandescent, high-pressure sodium, metal halide, and mercury vapor.
Incandescent lights produce all wavelengths of light and are closest to natural sunlight.
Incandescent is the least expensive light source to purchase, but the most expensive to operate because of short lamp life and low efficiency. Oddly enough it still remains the most popular type of lighting for residential landscapes. It has better color emission than mercury, but not quite as good as incandescent. Mercury vapor lamps emit light in the blue-green range which accentuates the green color of plants. High-pressure sodium lights are highly efficient.