A flower is a "solid" object and thus radiates a thermal blackbody spectrum. However, a flower isn't hot enough to radiate significantly in the visible part of the
spectrum (it does radiate in the infrared, however). Like most normal objects, it is seen visibly by reflection. If illuminated by white light (e.g., sunlight), the visible
spectrum of the rhododendron will be as shown above. The green portion of the illuminating light is absorbed by the flower so that only the blue and red parts are reflected, leading to a "blue-red"
or magenta color.
Spectrum of Magenta Rhododendron