Many, if not most, plants considered decorative flowers originated as weeds, which if attractive enough would sometimes be tolerated by farmers because of their appeal. This led to an artificial selection process, producing ever-prettier (to humans) flowers. This is thought to have occurred for the entire history of agriculture, perhaps even slightly earlier, when people tended to favor naturally occurring food-gathering spots. This may also explain why many flowers function as companion plants to more useful agricultural plants; they had evolved that symbiotic relationship with the food plants before either was domesticated, and therefore was found in the same area, convenient to be selected as an attractive plant.
Once domesticated, though, most flowers were grown either separately or as part of gardens having some other primary function. In the West, the idea of gardens dedicated to flowers did not become common until the 19th century, though in fact many modern gardens are indeed flower gardens. Flower gardens are, indeed, a key factor in modern landscape design and even architecture, especially for large businesses, some of which pay to have large flower gardens torn out and replaced entirely each season, in order to keep the color patterns consistent.
Well, that's some light on how flower garden became an important part of a landscape design :)
Cheers..!!!
P.S : I seriously dont know the name of the flowers. Interested people can contact my mother..!! A hard core garden lover and a Botany teacher :D (she would loves to explain too :D)