Frondosity (from Latin frondōsus meaning 'leafy') is the property of an organism that normally flourishes with fronds or leaf-like structures.
Many frondose organisms are thalloid and lack the organization of tissues into organs, with the exception of ferns.
Frondosity is significant mainly for distinguishing particular types of macroscopic algae, and in paleobotany and paleontology, by analyzing features present in fossil biota.
Frondose macroalgae are relevant to the ecology of many marine and coastal ecosystems. Large frondose algae play an important role in the creation and functioning of healthy ecosystems from kelp forests to similar habitats.[1] Yet, in coral reefs, frondose seaweed can be recognized as harmful due to the link between excessive blooms and coastal eutrophication.[2]