The Green does not refer to a single plant, or type of plant but rather the phenomenon of rapid unexplained plant growth that has been covering swathes of the Mojave. It is a combination of plants both familiar and strange to the people of New Vegas. Whether or not these plants are returning pre-war species or new species is unknown. The exact process of growth is always changing but it follows the general pattern of creepers and vines, followed by mosses and lichen, ferns and grasses and in just a few weeks entire bushes and small saplings.
While some of the growth is harmful or toxic there are many edible, medicinal and beautiful specimens as well. Nonetheless unchecked growth of the Green has taken over the community of Westside and driven the people into Freeside and the wider Mojave. While primarily in the Northwest region of the Mojave the Green has recently been seen to “jump” to new areas without any connection to the original growths. Some towns as far south as Novac and Cottonwood Cove have reported unexplained plant growth.
At the center of these outbreaks of Green is the fungus Beauveria Mordicana which causes the deadly illness known as "Greenlung" or the "McCarran Cough". Greenlung is a respiratory infection that cannot be transmitted between people and only originates from exposure to spores of Beauveria Mordicana. Nearly always fatal Greenlung begins with a simple cough, then the patient begins to experience shortness of breath. After a few days heavy fevers sap strength from the body and the cough becomes sharp and haggard. Most die within a week or two, either from a closing of the airway or from fever. Some have been known to last as long as six weeks before dying, usually to another disease as the body has become so weakened. Those very fortunate few who have survived an infection of Greenlung forever suffer from shortness of breath and painful migraines that come and go.
The map below details the spread of the Green with the bright green areas representing significant "hotspots" of the plant growth and the presence of Beauveria Mordicana.
Camp McCarran: Sometimes referred to as "Fort Garden", Camp McCarran was the at the center of the outbreak of the Green. While the foundations of the Forest had already been set, it wasn't until McCarran bloomed that the Mojave became truly aware of the Green. Very few people have ventured into the camp since it was closed by the NCR. Of those who have entered some return and tell of an unrecognizable jungle full of strange plants and animals. Adventurous individuals sometimes brave the dangers to retrieve certain items or plants of value. But those that don't disappear into the Green often return sick or infected with some kind of parasite.
Old Mormon Fort: Once a fortified hospital for the Followers of the Apocalypse, after the break out of McCarran cough the fort couldn't handle the number of patients it was receiving. The fungus Beauveria Mordicana overwhelmed the staff the Followers were forced to close the hospital. Like McCarran, the walls are sometimes scaled by those dauntless enough, but the danger inside is real.
The Brackenwood: The heart of the Green, the Brackenwood is a dense overgrown forest centered around Vault 22. The Brackenwood is covered in a vast variety of plants both strange and beautiful. So prolific is the plant life here that is has started to affect the weather. Pulling in water vapor from the surrounding region it condenses into clouds which rain upon the Brackenwood further feeding the growth and starting the cycle all over again. A dense mist saturates the inner region and there have been reports of strange animals and unnatural sounds from those who have delved that deep and returned to speak about it.
The Grove: A woodland covering the hills and mountains near the former settlement of Jacobstown. Primarily consisting of aspens, conifers, and sequoias the Grove is home to a large population of unnatural predators. Striking from the shadows and misty undergrowth they've remained unseen, with some people believing it to be a large population of nightstalkers. Since the growth of the Green into the mountains the mutants in Jacobstown haven't been see or heard from. Rumors say they left, pushed out by the growth and continued North. Others claim they were killed or even still live there, now truly isolated from others.