I need tips for gardening.

There is a beautiful garden. It has variety of flowers with different colors, growing in different sections. However, one particular flower from one section is quantitatively outgrowing others and spreading all over. As a consequence, the garden over the course of time is turning into a lot that is pretty much covered with only one type of flower and now the blossoms in the garden is retained by characteristics of that one invasive flower. There are only couple few spots left in the garden where resistant flowers remain. Would you let the garden be taken over by that invasive flower? Or would you maintain the diverse nature of the garden as before? What do you think is best. What should I do?