Smudge Pot

From Wikipedia

Smudge pot from Central Florida burning. This one has been recently lit off, as the exhaust on a fully hot pot becomes almost invisible with a mere hint of red/orange flame. Note that the filler/flue cap is in the fully open position (all holes open). A smudge pot (also known as a choofa or orchard heater) is an oil-burning device used to prevent frost on fruit trees. Usually a smudge pot has a large round base with a chimney coming out of the middle of the base. The smudge pot is placed between trees in an orchard. The burning oil creates some heat, a large amount of smoke, particulates, carbon dioxide, and water vapor. It was believed that this deliberate smog forms a "blanket" that blocks infrared light, thereby preventing radiative cooling that would otherwise cause or worsen frost. (Low clouds can have a similar "infrared blanket" effect, which is why cloudy nights tend to be warmer than clear-sky nights.) However, it has been learned that smoke actually does not prevent the radiation heat loss of an orchard as infrared waves of long wavelengths can pass through carbon particles in smoke. Smoke even prevents the penetration of the shortwave radiation from the sun, leading to prolonged needed orchard heating in the morning.

In 1907, a young inventor, W. C. Scheu, at that time in Grand Junction, Colorado, developed an oil-burning stack heater that was more effective than open fires in heating orchards and vineyards. In 1911, he opened Scheu Manufacturing Company in Upland, California, and began producing a line of orchard heaters. (The firm still exists in 2018.) The use of smudge pots became widespread after a disastrous freeze in Southern California, January 4–8, 1913, wiped out a whole crop. 

Smudge pots were commonly used for seven decades in areas such as California's numerous citrus groves and vineyards. The Redlands district had 462,000 orchard heaters for the winter of 1932–33, reported P. E. Simpson, of the supply department of the California Fruit Growers Exchange, requiring 3,693,000 gallons of oil for a single refilling, or about 330 tank car loads. To fill all of the smudge pots in Southern California one time required 2,000 tank car loads.

Smudge pot use in Redlands, California groves continued into the 1970s, but fell out of favor as oil prices rose and environmental concerns increased.