It happens almost every year somewhere in the ecogarden. A large, robust grassy plant sprouts up, growing rapidly. Although I usually pull out almost all grass plants because they tend to be incredibly invasive, there are several kinds of grass that might be left alone. One of them is wheat.
This one sprouted in a container alongside verbena and sorrel. All winter it grew, and in early spring it went to seed. Now its huge spikes are nodding, laden with heavy grain. I don’t know where the original seed came from, but this variety of wheat now seems to be a permanent part of the biota in the ecogarden.
There are several species of wheat, with complex genetics. Some have two, four, or even six complete sets of chromosomes. It has been cultivated for at least 11,000 years after originating in the middle east. Like many old food crops, it has been selectively bred by humans until it is distinctly different from its wild ancestors.
This Wikipedia article has lots of great information about wheat and its history.