Sometimes this glow is so strong that people call the Park Service hazmat team. But it's all a natural phenomenon known as foxfire produced by the jack-o-lantern mushroom.
How bioluminescence works: When the pigment luciferin and the enzyme luciferase combine in the presence of oxygen, the reaction produces energy, which is released as light.
It's the same reaction that lights up the firefly. Unlike the firefly, the mushroom can't turn the process off and on at will, and so glows all the time. During the day or on bright nights, we already see so much light that we don't notice the dim glow of the foxfire.
More information and pictures here: http://io9.com/when-forests-glow-green-in-the-night-505135959
The bioluminescence phenomenon - nature glows everywhere: ocean plankton, fish, and assorted other animals - http://www.bbc.co.uk/nature/21011428