Sentence:  Most plants are hermaphrodite, even if some of them (hazel, for example) keep their male and female flowers apart. But some plants are <WSD>dioecious</WSD>, i.e. they have separate sexes. Some of our most familiar wild plants, such as nettle and red campion, are <WSD>dioecious</WSD>. If your holly never has any berries, that's probably because it's a male. 
Meaning of the word marked with <WSD> tags:  Having the male and female reproductive organs on separate plants (of the same species) rather than different parts of the same plant.