Roses are red but don't smell as nice when in bed.
New research shows that people are more sensitive to the smell of roses when sitting than lying down.
The study adds to previous findings which suggest that lying down impairs other senses, such as hearing and spatial perception.
Scientists say they can only speculate as to the biological necessity of the difference.
Volunteers were exposed to sixteen different concentrations of rose odour while sitting upright or lying down.
More than 60% had decreased sensitivity to the rose smell when in a lying position.