Why the genus Artemisia is a botanical puzzle that defies simple classification

Nature · Published 3 October 2026 Swipe more like this →

In short: With nearly 500 species, the Artemisia genus—encompassing everything from culinary tarragon to rugged sagebrush—is notoriously difficult to categorize. While traditional methods relied on floral shapes, modern molecular data reveals a complex history of convergent evolution, where unrelated plants developed identical traits, constantly challenging how we organize this diverse group.

Erected by Carl Linnaeus in 1753, the genus Artemisia takes its name from the Greek goddess Artemis, potentially honoring the queen and medical researcher Artemisia II of Caria, who died in 350 BC. These hardy shrubs and herbs thrive in temperate, dry, or semiarid regions across both hemispheres. Many species are easily recognized by their aromatic, bitter leaves, which are often coated in fine white hairs—a defense mechanism against herbivores fueled by potent chemical compounds like sesquiterpene lactones.

Classifying these plants has proven remarkably difficult. For decades, botanists grouped them based on physical traits like flower head structure, but molecular research—particularly since 2000—has frequently overturned these assumptions. For example, the North American sagebrushes of section Tridentatae were once thought to be closely related to Old World species in the genus Seriphidium. However, studies by McArthur and others in 1981, followed by later DNA sequencing, revealed that their similarities were actually the result of convergent evolution, not shared ancestry.

The Tridentatae subgenus is particularly complex because of its high degree of genetic diversity within populations rather than across distinct species. This fluidity allows for frequent hybridization, which complicates efforts to map their evolutionary tree. While some groups like the subgenus Dracunculus—which includes the spice tarragon—are well-resolved by DNA analysis, others remain in flux. As of June 2024, Plants of the World Online recognizes nearly 500 species, yet researchers continue to debate the boundaries of these lineages as new genetic evidence emerges.

Ultimately, the study of Artemisia highlights the limitations of relying solely on morphology. Inflorescence characteristics, once considered reliable markers, have been shown to evolve in parallel multiple times. Today, scientists look to chloroplast and ribosomal DNA to clarify these relationships, though the rapid radiation of certain subgenera means that the full story of their evolution remains a work in progress.

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