Seed plants

Arepa

Arepa: round flat maize-dough bread, staple of Colombia and Venezuela, pre-Columbian in origin; name from Cumanagoto erepa, first documented 1548. Venezuelans stuff it as a main dish; Colombians eat thinner arepas as accompaniment.

Argan oil

Argan oil, a plant oil from kernels of the endemic argan tree (Argania spinosa) of southwest Morocco; UNESCO-listed traditional extraction, oleic/linoleic-rich composition, γ-tocopherol, schottenol and spinasterol sterols, and the world's most expensive vegetable oil.

Argemone

Argemone, prickly poppy (Mexican poppy, Argemone mexicana), a Papaveraceae genus of 33 spiny yellow-sapped herbs native to the Americas and Hawaii; A. mexicana seed oil causes epidemic dropsy.

Argemone mexicana

Argemone mexicana (Mexican prickly poppy, cardo santo), a prickly annual Papaveraceae herb native to Central America, pantropical weed and medicinal plant whose sanguinarine-rich seed oil causes epidemic dropsy when it adulterates mustard oil.

Argentina anserina

Argentina anserina (silverweed, silverweed cinquefoil; formerly Potentilla anserina) is an allotetraploid stoloniferous Rosaceae perennial of temperate wetlands across the Northern Hemisphere, invasive in Patagonia, IUCN least concern.

Argyreia nervosa

Argyreia nervosa, Hawaiian baby woodrose or elephant creeper, is a Convolvulaceae liana native to the Indian subcontinent to Myanmar whose seeds contain 0.5–0.9% ergoline alkaloids including LSA, giving LSD-like but sedating effects.

Aria torminalis

Aria torminalis, the wild service tree (syn. Sorbus torminalis, Torminalis glaberrima), is a suckering Rosaceae tree of Europe to Iran and NW Africa, with chequer fruits, prized timber, and IUCN Least Concern status.

Ariocarpus retusus

Ariocarpus retusus (star rock, living rock, false peyote) is the type species of the living rock cacti, a spineless grey cactus from northeastern Mexico, 10–25 cm across, white autumn flowers, IUCN Least Concern but CITES Appendix I.

Ariocarpus scaphirostris

Ariocarpus scaphirostris (also spelled scaphirostrus), the Nuevo León living-rock cactus, is an endangered CITES Appendix I cactus endemic to Nuevo León, Mexico, with boat-shaped tubercles and a population down over 80% in 20 years.

Arisaema

Arisaema (天南星属), jack-in-the-pulpits or cobra lilies, is a genus of about 200 aroid herbs (Araceae) native from Africa and Arabia through Asia to North America, with hooded spathes, sex-changing plants, 15 sections, and medicinal rhizomes.

Arisaema triphyllum

Arisaema triphyllum, jack-in-the-pulpit (also Indian turnip, wake robin), a North American Araceae herb with hooded spathe, size-dependent sex change, fungus-gnat pollination, and calcium oxalate toxicity.

Aristida

Aristida (three-awn, threeawns, speargrass) is a genus of about 300 tufted Poaceae grasses with three-awned lemmas, in Aristidoideae, mostly C4, of tropical and subtropical arid grasslands worldwide.

Aristolochia

Aristolochia (birthwort, Dutchman's pipe) is a cosmopolitan genus of about 350–569 species in Aristolochiaceae with trap flowers pollinated by flies, containing carcinogenic aristolochic acids.

Aristolochiaceae

Aristolochiaceae, the birthwort family (Aristolochiaceae Juss., 1789), is a Piperales family of climbers and herbs including Aristolochia and Asarum, known for trap-pollinated flowers and nephrotoxic, carcinogenic aristolochic acids.

Armeria

Armeria (thrift, sea pink) is a genus of about 100–260 perennial Plumbaginaceae herbs with basal rosettes and globose flower heads, centered in the Mediterranean; Italy is its second biodiversity hotspot with 10 endemic species per a 2026 revision.

Armillaria ostoyae

Armillaria ostoyae, the honey mushroom or shoestring fungus, is a parasitic forest pathogen; its Oregon "Humongous Fungus" genet covers 2,385 acres in Malheur National Forest and is considered the largest known living organism.

Arnica

Arnica, a Northern Hemisphere genus of about 31 Asteraceae species, is the source of Arnica montana, used externally for bruises and sprains; internal use is toxic and homeopathic efficacy is unproven.

Arnica montana

Arnica montana (mountain arnica, Echte Arnika) is a European Asteraceae perennial whose yellow flower heads yield helenalin sesquiterpene lactones used topically for bruises and sprains; endangered in Germany, CITES-listed, EU traditional-use herbal monograph.

Aronia

Aronia, known as chokeberry or chokeberries, is a genus of deciduous shrubs in the rose family native to eastern North America, grown for its dark, polyphenol-rich fruit used in juice and wine.

Aronia melanocarpa

Aronia melanocarpa (black chokeberry) is a North American Rosaceae shrub grown for astringent, polyphenol- and anthocyanin-rich berries used in juices and functional foods; human RCT meta-analyses show no significant cardiometabolic effects.

Arracacia xanthorrhiza

Arracacia xanthorrhiza (arracacha, Peruvian parsnip) is an Andean Apiaceae herb domesticated about 3000 years ago for its starchy storage root, grown at 600–3600 m in Brazil, Colombia, and other Andean countries, propagated by cormels.

Arrhenatherum

Arrhenatherum (oatgrass, false oat-grasses) is a genus of seven accepted perennial grasses in Poaceae, Aveninae, native from Macaronesia and Europe to Central and West Asia and NW Africa; its best-known species is A. elatius, tall oatgrass.

Arrhenatherum elatius

Arrhenatherum elatius, false oat-grass or tall oatgrass (Avena elatior), a perennial Poaceae grass native from Europe to Iran, grown for hay and pasture; the bulbous subspecies bulbosum is the arable weed onion couch.

Arrowroot

Maranta arundinacea (arrowroot, araruta, garut) is a perennial Marantaceae herb native from Mexico to tropical America, grown for easily digestible starch from its rhizomes, commercially centered on St Vincent.

Artemisia

Artemisia, known as wormwood, mugwort, and sagebrush, is a genus of about 540 aromatic herbs and shrubs in the daisy family, source of the antimalarial drug artemisinin.

Artemisia absinthium

Artemisia absinthium (wormwood, absinthium), Asteraceae perennial of Europe to Siberia, W. Himalaya, N. Africa; source of absinthe's thujone, EMA traditional use for appetite loss and dyspepsia, invasive in North America.

Artemisia annua

Artemisia annua (qinghao), annual Asteraceae herb native from North Africa to Eurasia; sole natural source of the antimalarial sesquiterpene artemisinin, made in glandular trichomes and the basis of ACT drugs.

Artemisia tridentata

Artemisia tridentata, big sagebrush, is an aromatic evergreen Asteraceae shrub dominating 62 million hectares of western North America, with basin, mountain, and Wyoming subspecies on distinct soils and elevations, killed by fire and regenerating only from seed.

Artemisia vulgaris

Artemisia vulgaris, common mugwort (ai-yeh, moxa), a perennial Asteraceae herb native to temperate Eurasia and North Africa, naturalized in North America; medicinal and culinary herb with thujone limits, allergy risk, and invasive status in the northeastern US.