A close-up view of Aloe vryheidensis flowers with dark-colored nectar visible.

Floral nectar is offered by plants to animals as a reward for pollination. Nectar is usually clear and contains sugar and trace amounts of amino acids. Colored nectar also occurs, but is less common. The nectar of Aloe vryheidensis contains phenolic compounds that give it its dark brown color and a bitter taste. The main effect of the phenolics appears to be to repel certain nectarivores with a bitter taste and attract others with its coloring. The birds that are the most effective pollinators for this species do not seem to be affected by the bitter taste and are attracted to flowers with dark nectar. This photograph originally appeared on the cover of Ecology (87:11) in November of 2006.