Supplemental electric lighting for greenhouses may be essential for extending the growing season in northern climates, but it comes with a not-so-hidden cost: environmental light pollution. The consequences of this pollution may range from irate neighbours in rural areas to municipal bylaws that may prohibit the use of supplemental lighting during certain hours of the night or altogether.
Searching for information on light pollution online will yield plenty of results. However, it soon becomes apparent that it does not apply to greenhouse lighting. Most of the discussion concerns astronomical light pollution, which is of interest to both amateur and professional astronomers, and where the focus is on outdoor lighting for roadways and parking lots. There are also discussions of “light trespass” onto residential properties from adjacent street lighting, which is rarely a concern for commercial greenhouses.