Why the spiderwort and water hyacinth share a surprising botanical family tree

Gardening · Published 3 October 2026 Swipe more like this →

In short: The Commelinales order brings together plants as diverse as terrestrial spiderworts and aquatic water hyacinths. While they look worlds apart, these 800-plus species are linked by hidden cellular traits and shared evolutionary history. Discover how modern molecular science reorganized these plants, moving them away from the lily order forever.

The Commelinales order comprises over 800 species of mostly tropical and subtropical herbs, organized into five distinct families: Commelinaceae, Pontederiaceae, Haemodoraceae, Philydraceae, and Hanguanaceae. The largest of these is Commelinaceae, the spiderwort family, which contains 652 species. These plants range from terrestrial herbs and climbers to epiphytes, including popular ornamentals like the spiderwort genus (Tradescantia) and the dayflower genus (Commelina). Other families, such as the bloodwort family (Haemodoraceae), are known for the bright red pigments in their flowers and roots, while the water hyacinth family (Pontederiaceae) consists primarily of aquatic plants.

Botanists once grouped many of these families within the lily order, Liliales. However, the Angiosperm Phylogeny Group (APG) reclassified them based on shared characteristics that suggest a closer evolutionary relationship. These markers include specific stomatal complexes with subsidiary cells, the presence of ultraviolet-fluorescent compounds in cell walls, and a particular type of epicuticular wax. Together with grasses and gingers, these plants are now often referred to as Commelinids, representing a significant shift from older classification systems like the 1981 Cronquist system, which relied solely on morphological data and placed these families in unrelated groups.

The order exhibits remarkable biological variety. Some members, particularly in the water hyacinth family, utilize a pollination mechanism called heterostyly, where flowers possess varying lengths of styles and anthers to encourage cross-fertilization. While most members are small to large herbs with rhizomatous growth, their leaves and floral structures vary widely, from hypogynous to epigynous arrangements. Even the placement of the Hanguanaceae family was long debated; while molecular evidence now links it to Commelinaceae, some morphological traits have historically suggested a connection to the ginger order, Zingiberales. This ongoing refinement of plant taxonomy highlights how molecular data continues to reshape our understanding of the natural world.

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