Coriaria L. is a genus of approximately 15 species of deciduous shrubs, subshrubs, and small trees in the monotypic family Coriariaceae, placed in the order Cucurbitales. The genus was described by Linnaeus in his Species Plantarum (1753), with Coriaria myrtifolia as the type species. Plants typically reach around 1–5 metres in height depending on species, with opposite or whorled simple leaves 2–9 cm long that lack stipules. Flowers are small and greenish, arranged in racemes 2–30 cm long, and are hermaphroditic. The fruit is a small, shiny berry — most commonly black, though occasionally red or yellow — that is highly poisonous in the majority of species.
One of the genus's most ecologically notable characteristics is the presence of nitrogen-fixing root nodules, making Coriaria one of the very few non-legume angiosperms capable of atmospheric nitrogen fixation. This trait allows certain species to colonise nutrient-poor soils, including steep cliff faces and disturbed ground.
The genus has a markedly disjunct distribution across warm-temperate zones worldwide, spanning the Mediterranean basin, the Himalayas, East and Southeast Asia (including China and Japan), New Guinea, the Pacific islands (Fiji, Samoa, Solomon Islands, Vanuatu, the Society Islands, and the Chatham Islands), New Zealand, and from Mexico south through the Andes to southern South America. This fragmented range has attracted considerable biogeographic interest, with a fossil record extending to Miocene pollen in Europe and possibly as far back as the Campanian of Antarctica (~82 million years ago).
Most species are strongly toxic to livestock and humans; the berries and seeds contain the sesquiterpene lactone tutin and related compounds. New Zealand's tutu species (C. arborea, C. sarmentosa, and relatives) are well-known stock poisons, while the Mediterranean C. myrtifolia has a long history as a tanning plant. The Andean and Chilean C. ruscifolia has been used as rat poison. One exception is C. terminalis (Himalaya/China), whose fruit is reported edible. Several species also yield black dyes and inks from their leaves and bark.
Etymology
The genus name Coriaria derives from the Latin corium (leather/hide), referring to the use of the bark and leaves of the Mediterranean species C. myrtifolia in tanning leather. This tanning use was well established in southern Europe before the genus was formally described by Linnaeus in 1753. The vernacular name "tutu" used in New Zealand is of Māori origin and applies broadly to the local species of the genus.
Distribution
Coriaria shows a strikingly disjunct warm-temperate distribution spanning five continents and several oceanic island groups. In the Mediterranean basin it is represented by C. myrtifolia (France, Italy, Greece, Spain, Algeria). In Asia, species occur from Pakistan and the Himalayas (East Himalaya, Nepal — C. nepalensis) across China (north-central, south-central, and southeast regions) to Japan (C. japonica) and into New Guinea. In the Pacific, the genus is recorded from Fiji, Samoa, the Society Islands, Solomon Islands, Vanuatu, and the Chatham Islands off New Zealand. New Zealand itself hosts several endemic species (the "tutu" group). In the Americas, the genus ranges from Mexico and Central America (Guatemala, Costa Rica, Colombia, Ecuador) southward through the Andes to central and southern Chile and Argentina. The species C. ruscifolia is the dominant South American representative. The overall distribution pattern has been interpreted as a Gondwanan or Tethyan relict track, consistent with the ancient fossil record of the family.
Taxonomy
Coriaria L. is the sole genus in the family Coriariaceae (Cucurbitales). It was established by Linnaeus in Species Plantarum: 1037 (1753), with the Mediterranean C. myrtifolia as the type. POWO recognises 15 accepted species including two hybrid taxa; GBIF records 31 descendant taxa (including synonymised names). Two heterotypic synonyms are recognised: Heterocladus Turcz. (1847) and Heterophylleia Turcz. (1891), both now subsumed under Coriaria. Placement of the family within Cucurbitales — alongside cucumber and gourd relatives — reflects molecular phylogenetic work conducted since the early 2000s and is supported by Govaerts' World Checklist of Seed Plants. Coriariaceae is the only family in the order capable of actinorhizal (non-legume) nitrogen fixation.
Ecology
Coriaria occupies a wide range of open to semi-shaded, often disturbed or nutrient-poor habitats. In the Andes the genus colonises steep cliffs and rocky terraces; in New Zealand, tutu species are characteristic of forest margins, landslips, river terraces, and scrubland. A defining ecological trait is the genus's capacity for actinorhizal nitrogen fixation through root-nodule symbiosis — a mechanism usually associated with legumes but here operating through actinobacterial partners. This allows Coriaria to pioneer low-fertility substrates and become a dominant early-successional shrub after disturbance. Plants spread locally through rhizomes, forming dense clonal colonies. The highly toxic berries and foliage deter most mammalian herbivores, though bird dispersal of seeds is documented in New Zealand.
Cultivation
Coriaria species are occasionally grown as ornamental shrubs in temperate gardens, valued for their graceful arching branches, attractive foliage, and shiny berries. They prefer a well-drained loamy soil in a sunny, sheltered position and will tolerate light shade. Most cultivated species are hardy to approximately −5°C (USDA zones 7–10), though hardiness varies by species — C. japonica from Japan is somewhat hardier. Established plants spread by rhizomes and can form large colonies. The highly toxic nature of the berries must be noted clearly in any garden setting accessible to children or pets.
Propagation
Coriaria can be propagated by seed or vegetatively. Seeds should be sown in late winter (February–March) in a greenhouse; germination takes one to three months at 15°C. Half-ripe cuttings approximately 7 cm long with a heel can be taken in July–August and rooted in a cold frame. Established clumps can also be divided in spring, taking advantage of the genus's rhizomatous habit to produce rooted divisions.
Cultural uses
Members of Coriaria have been used across their range for tanning, dyeing, and as poisons. The Mediterranean C. myrtifolia ("redoul") is rich in tannins and was historically important in the leather industry of southern France, Italy, and Spain. Bark and leaves of multiple species yield a black dye and ink. In southern Chile, C. ruscifolia (known locally as "deu" or "huique") has been used as a rat poison. In New Zealand, Māori recognised tutu (C. arborea, C. sarmentosa, and related species) as lethally poisonous to people and livestock; the juice of the ripe berries — carefully separated from the poisonous seeds — was reportedly consumed in small quantities or used ceremonially. The fruits of the Himalayan/Chinese C. terminalis are described as edible. Medicinally, the fruit of some species reportedly has hallucinogenic properties, historically attributed to the sesquiterpene tutin content.
