Artemisia

Taxonomy

The genus was erected by Carl Linnaeus in 1753. The name Artemisia derives from the Greek goddess Artemis (Roman Diana), the namesake of Greek Queens Artemisia I and II. A more specific reference may be to Artemisia II of Caria, a botanist and medical researcher (also a queen and naval commander), who died in 350 BC.

Classification

Classification of Artemisia is difficult. Divisions of Artemisia prior to 2000 into subgenera or sections have not been backed up by molecular data, but much of the molecular data, as of 2006, are not especially strong. The following identified groups do not include all the species in the genus.

Subgenera Artemisia and Absinthium are sometimes, but not always, considered the same. Subgenus Artemisia (originally Abrotanum Besser) is characterized by a heterogamous flower head with female outer florets and hermaphrodite central florets, and a fertile, glabrous receptacle. Absinthium DC, though sometimes merged with subgenus Artemisia is characterized by heterogamous flower head with female outer florets and hermaphrodite central florets, and a fertile, hairy receptacle. Generally, previously proposed monotypic and non-monophyletic subgenera have been merged with the subgenus Artemesia due to molecular evidence. For example, in 2011 using ribosomal DNA analysis of their own and a review of molecular data (such as ITS sequence analysis) of others, S. Garcia and colleagues argued that it was logical to rename several Sphaeromeria and Picrothamnus (formerly designated sister genera to Artemisia) species as Artemisia, as well as to revert some Sphaeromeria species back to Artemisia, where they had been categorized previously. Part of this was due to research by Watson and colleagues, who found that the four subgenera were not monophyletic except for Dracunculus, after analyzing and matching the internal transcribed spacers of nuclear ribosomal DNA from many Seriphidium and Artemisia species, and the related genera Arctanthemum and Dendranthema. The authors concluded that inflorescence morphology is not alone reliable for categorizing the genus or some subgenera, as qualities that previously demarcated them (such as homogamous, discoid, ray-less inflorescences) seemed to have undergone paralleled evolution up to seven times. Picrothamnus Nutt. ("bud sage"), now considered Artemisia spinescens and Sphaeromeria Nutt. ("chicken sage") are some examples, both endemic to North America.

Section Tridentatae consists of eleven to thirteen species of coarse shrubs often known colloquially as "sagebrushes", which are very prominent parts of the flora in western North America. In some classifications, they have previously been considered part of the genus or subgenus Seriphidium, although recent studies have contested this lineage to Old World species. Tridentatae was first articulated as a section by Rydberg in 1916, and it was not until McArthur et al. in 1981 that Tridentatae was elevated to a separate subgenus from Seriphidium. The principal motive for their separation was geographical distribution, chemical makeup, and karyotype. Much of the debate surrounding Tridentatae is phytogeographic, thus habitat and geography are frequently cited when understanding the evolution of this endemic North American subgenus. Evolutionary cycles of wet and dry climates encouraged "diploid and polyploid races which are morphologically similar if not indistinguishable" (McArthur 598).

Species

As of June 2024, Plants of the World Online accepted almost 500 species. Below are named some of the most notable Artemisia species:

Artemisia abrotanum L. – southernwood, southern wormwood, slovenwood, abrotanum, old-man, lad's love

Artemisia absinthium L. – grand wormwood, absinthium

Artemisia afra Jacq. ex Willd. – African wormwood, African sagebrush

Artemisia alba Turra – camphor southernwood

Artemisia aleutica Hultén – Aleutian wormwood

Artemisia annua L. – annual wormwood, sweet sagewort, sweet Annie

Artemisia arborescens L. – tree wormwood

Artemisia arbuscula Nutt. – little sagebrush, low Sagebrush, black sage

Artemisia arenaria DC.

Artemisia argyi H.Lév. & Vaniot – Chinese mugwort

Artemisia austriaca Jacq.

Artemisia bhutanica Grierson & Spring.

Artemisia biennis Willd. – biennial sagewort, biennial wormwood

Artemisia bigelovii A.Gray – Bigelow sage, Bigelow sagebrush

Artemisia caerulescens L.

Artemisia californica Less. – coastal sagebrush, California sagebrush

Ecology

Artemisia species are found on every continent except Antarctica, and have become part of many ecosystems around the world as a result. Below is currently a partial view of the importance of Artemisia species in ecosystems around the world.

North America

In North America, several species of Artemisia have become important parts of local environments, with wide adaptability. Artemisia papposa described by S.F.Blake & Arthur Cronquist can grow in the harsh, dry expanses of alkali flats, but also adapts to meadowlands.

Sagebrushes like A. papposa (of the Tridenteae subgenus) in general are found in the north and southwest areas of the North American continent. In the Intermountain West, in a habitat known as Sagebrush Steppe, A. tridentata, A. tripartite, and A. arbuscula grow alongside various grasses and species of bitter bush, creating an important environment for mule deer, pygmy rabbits, antelopes, and the sage grouse. Understanding the phylogenetic relationships among the sagebrushes has been helpful in understanding the relationships among these plants and their environments, as well as learning more about how these plants formed these communities over long stretches of time. Sagebrushes, which include A. ludoviciana and A. tridentata among others, can often also be found growing near junipers, particularly in the Elkhorn Mountain region, where the Juniper Woodlands form an ecosystem which provide cover for many animal species in both summer and winter months and storms. Because the habitat should burn only every 400–600 years, with sagebrush shrubs living as long as 200 years (though potentially typically 88), this particular combination of Artemisia with other flora form an enduring habitat. As it often goes, however, governments and farming businesses have often cleared sagebrush-juniper communities to create land for cow and domestic animal feedcrops, and Artemisia species may be declining due to this and invasive species such as cheatgrass. Destabilization of the vegetation creates higher risk of fires, causing concern among the local conservation and wildlife groups.

Due to their often extensive rhizome systems and other potential characteristics, however, some Artemisia species are often resilient to mowing or pulling, giving some species of Artemisia the ability to easily become invasive if introduced to comfortable, though non-native habitats.

A. annua (native to Eurasia) is found in wetland habitats, and though it has been naturalized in much of North America it is considered weedy or invasive by some localities, such as Kentucky.

This is particularly true of Artemisia vulgaris, known as "common mugwort", in North America, where it was introduced by European colonists and settlers in the 1600s, when Jesuit priests and other colonizers may have first brought the herb for ointments and teas and likely also let into port cities via ballast dumping. Artemisia vulgaris will grow in dense groups and out-compete other plants in an area, in part due to its ability to grow on poorly enriched soils. Disturbed habitats, cities and roadsides or parking lots can easily become a field of A. vulgaris, which is the Artemisia species designated as invasive by New York State.

Cultivation and uses

Historical uses

Historically, Artemisia species were used in the attempted cure of various medical ailments, particularly related to women's health. In the Middle Ages, Artemisia sp. were regarded as herbs of significant medical power, and described as "the most important master against all exhaustions". By the Renaissance, Artemisia sp. (particularly A. absinthium) was used particularly in the cure of digestive ailments, though the use of species such as A. vulgaris in women's health still persisted.

Artemisia species (likely A. vulgaris and A. latifolia) were described by the Greco-Roman physician Dioscorides (c. 40–90 AD) in his De materia medica as being used for "driving out the menstrual flow" and as an "abortifacient". Historian John Scarborough (1940-2022) argued that Dioscorides' discussion of Artemisia sp. was an adaptation of folklore medicine that was commonly used in Asia Minor and Thrace. Learned medicine in the Middle Ages was largely based on humoral theory, which ascribed certain properties to herbs based on their use in heating/cooling and wetting/drying the body. A. vulgaris was described by the second century physician Galen (c. 129–216 AD) as having warming and drying effects, which recommended it to the treatment of urological diseases. The continued use of Artemisia as an abortifacient was described by twelfth-century women's health texts in the Trotula. This use was further integrated into university teaching by Johannes II Platearius (active 1120–1150) at the medical school of Salerno, who proscribed a "wine of the decoction of artemisia" as a cure to blocked menstrual flow.

Artemisia sp. continued to be used in women's health into the 16th century, and was described by Johann Wonnecke von Kaub in Gart der Gesundheit as the "mother herb", for use in "women's sickness". This continued in the English medical tradition as well, with mugwort (likely A. vulgaris) being described as a "an herb appropriated to the female sex" for use in "bringing down the menses" by the English physician Nicholas Culpeper's 1653 Complete Herbal.

In Anglo-Saxon medicine, Artemisia vulgaris (mugwort) and A. pontica were described as treatments for soreness, pains and aches. A. vulgaris and A. absinthium were used to repel midges (Old English mucgwyrt seems to be derived from mycg 'midge'), fleas and moths, intestinal worms, and in brewing (mugwort beer, mugwort wine) as a remedy against hangovers and nightmares.

Modern uses

The aromatic leaves of some species are used for flavouring. Most species have an extremely bitter taste. A. dracunculus (tarragon) is widely used as a culinary herb, particularly important in French cuisine.

Artemisia absinthium is used to make the highly potent spirit absinthe. Malört also contains wormwood. The aperitif vermouth is a wine flavored with aromatic herbs, but originally with wormwood.

Artemisia arborescens (tree wormwood, or sheeba in Arabic) is an aromatic herb indigenous to the Middle East used in tea, usually with mint.

A few species are grown as ornamental plants, the fine-textured ones used for clipped bordering. All grow best in free-draining sandy soil, unfertilized, and in full sun.

The largest collection of living Artemisia species, subspecies and cultivars is held in the National Collection of Artemisia in Sidmouth, Devon, UK, which holds about 400 taxa. The National Collection scheme is administered by Plant Heritage (formerly National Council for Conservation of Plants and Gardens, NCCPG) in the British Isles.

Medicinal uses

Artemisinin (from Artemisia annua) and derivatives are a group of compounds used to treat malaria. Treatments containing an artemisinin derivative (artemisinin-combination therapies) are now standard treatment worldwide for malaria caused by Plasmodium falciparum. Administering Artemisia annua as dried whole leaves may cause resistance to develop more slowly than if it is administered as pure artemisinin.

Tu Youyou received the 2015 Nobel Prize in Physiology or Medicine for her discovery of the semisynthetic derivatives. She conducted research on traditional Chinese medicine and potential contributions to cures for malaria, on the basis of folk medicine and ancient Chinese texts. From reviewing ancient Chinese texts, they found that the compound artemisinin was optimally extracted at lower temperatures, as high temperature water poured over sweet wormwood leaves destroyed essential treatment properties.

The World Health Organization does not support the promotion or use of Artemisia plant material in any form for the prevention or treatment of malaria. They note that the plant form of medication has several problems. These include a lack of consistent artemisinin content, the content being low enough that recurrence of malaria often occurs, that the use of the plant may contribute to widespread artemisinin resistance, and that the plant form is not effective in malaria prevention.