For hundreds of years, poets have written about flowers, using them to symbolize love and many other human emotions. Commonalities between humans and flowers may explain why the plants have such resonance in literature and popular culture.
Like humans, many varieties of flowers engage in sexual reproduction. Flowers have ovaries, ovules, and stamens analogous to male and female sexual organs.
Like humans, who may wear perfume or cologne to attract a sexual partner, flowers produce scents to attract pollinators such as bees and moths.
Flowers come in a variety of shades and hues, as do human hair and skin. Flower color is guided by evolutionary processes; some colors more efficiently attract pollinators or deter pests.
All living things on Earth have DNA. DNA molecules, organized into genes and chromosomes, encode the essential natures of both humans and flowers.
The most basic thing that flowers and humans share is life. Flowers and humans both are born, grow, reproduce, and then die. On the scale of the universe, there are not many things for which this can be said.