In actuality, humans consume the flowers of several plants as vegetables, including broccoli. The head of broccoli is actually the plant's buds. Left intact with the roots, these buds open to reveal small yellow flowers. In addition to the familiar green variety, it is available as a purple plant. Broccoli is a member of the Brassicaceae family, and closely related to cabbage, kale and bok choy, according to About.com.
As its name indicates, cauliflower is also a flower. Like its cousin broccoli, the edible flower buds grow in a closely packed head. The flower buds of cauliflower come in white, green and purple. Farmers harvest cauliflower as a perennial. While other members of the Cole family survive late frosts early in the growing season, cauliflower is less adaptable. HowStuffWorks says cauliflower also does not do well if temperatures get too hot.
Globe artichokes are another perennial that humans consume. Originating around the Mediterranean in southern Europe or North Africa, this thistle continues to grow wild in the region. The plant grows from 4 to 6 feet tall and has deeply lobed silvery leaves, almost 2 feet in length. The flowers produce a large head that includes an edible bulb and many triangular scales. Reference.com reminds consumers not to confuse globe artichokes with Jerusalem artichokes, which are tubers.