Kudzu is a plant that grows a foot a day, and is spreading across the southern part of the United States of America.
It can complete cover trees, buildings, and anything else about, dense enough you can't see what it grow over.
Its a great food for livestock.
If doomsday comes, then parts of the world will be overrun with kudzu and wild pigs feasting upon it and spreading ever farther.
Most parts of the plant can be eaten by humans. It can also be made into a variety of things.