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Thuja standishii.jpg
Thuja standishii foliage and cones
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Pinophyta
Class: Pinopsida
Order: Cupressales
Family: Cupressaceae
Subfamily: Cupressoideae
Genus: Thuja
Type species
Thuja occidentalis

Thuja ( /ˈθjə/ THEW-jə) [1] is a genus of coniferous tree or shrub in the Cupressaceae (cypress family). There are five species in the genus, two native to North America and three native to eastern Asia. [2] [3] [4] [5] The genus is monophyletic and sister to Thujopsis . Members are commonly known as arborvitaes (from the Latin term for 'tree of life'), thujas or cedars. [6]



Foliage of the cultivar 'Rheingold' Thuja 'Rheingold' in Autumn.JPG
Foliage of the cultivar 'Rheingold'

Thuja are evergreen trees growing from 10 to 200 feet (3 to 61 metres) tall, with stringy-textured reddish-brown bark. The shoots are flat, with side shoots only in a single plane. The leaves are scale-like and 1 to 10 mm (0.039 to 0.394 in) long, except young seedlings in their first year, which have needle-like leaves. The scale leaves are arranged in alternating decussate pairs in four rows along the twigs. The male cones are small, inconspicuous, and are located at the tips of the twigs. The female cones start out similarly inconspicuous, but grow to about 1 to 2 cm (0.39 to 0.79 in) long at maturity when 6–8 months old; they have 6-12 overlapping, thin, leathery scales, each scale bearing 1–2 small seeds with a pair of narrow lateral wings. [3]

The five species in the genus Thuja are small to large evergreen trees with flattened branchlets. The leaves are arranged in flattened fan shaped groupings with resin-glands, and oppositely grouped in 4 ranks. The mature leaves are different from younger leaves, with those on larger branchlets having sharp, erect, free apices. The leaves on flattened lateral branchlets are crowded into appressed groups and scale-like and the lateral pairs are keeled. With the exception of T. plicata, the lateral leaves are shorter than the facial leaves (Li et al. 2005). The solitary flowers are produced terminally. Pollen cones with 2-6 pairs of 2-4 pollen sacked sporophylls. Seed cones are ellipsoid, typically 9 to 14 mm (0.35 to 0.55 in) long, and mature and open the first year. The thin woody cone scales number from 4-6 pairs and are persistent and overlapping, with an oblong shape, they are also basifixed. The central 2-3 pairs of cone scales are fertile. The seed cones produce 1 to 3 seeds per scale, the seeds are lenticular in shape and equally 2 winged. Seedlings produce 2 cotyledons. [7] [8]

T. plicata bark, foliage Riesenlebensbaumstmrp.jpg
T. plicata bark, foliage
Old growth T. plicata, Olympic Peninsula, USA The Kalaloch Cedar - Flickr - rachel thecat.jpg
Old growth T. plicata, Olympic Peninsula, USA
Cultivars of T. occidentalis in an arboretum Podlaskie - Suprasl - Kopna Gora - Arboretum - Thuja occidentalis 'Smaragd' - plant.JPG
Cultivars of T. occidentalis in an arboretum
Thuja occidentalis cultivar 'EuropeGold' Thuja occidentalis 'EuropeGold'-201601-JAPAN.jpg
Thuja occidentalis cultivar 'EuropeGold'

A hybrid between T. standishi and T. plicata has been named as the cultivar Thuja 'Green Giant'.

Another very distinct and only distantly related species, formerly treated as Thuja orientalis, is now treated in a genus of its own, as Platycladus orientalis . The closest relatives of Thuja are Thujopsis dolabrata , distinct in its thicker foliage and stouter cones, and Tetraclinis articulata (Ancient Greek θυία or θύα, formerly classed in the genus and after which Thuja is named), distinct in its quadrangular foliage (not flattened) and cones with four thick, woody scales.

The genus Thuja, like many other forms of conifers, is represented by ancestral forms in Cretaceous rocks of northern Europe, and with the advance of time is found to migrate from northerly to more southerly regions, until during the Pliocene period, when it disappeared from Europe. Thuja is also known in the Miocene beds of the Dakotas. [9]



Stull et al. 2021 [10] [11]

T. plicata

T. koraiensis

T. sutchuenensis

T. occidentalis

T. standishii


The five extant species are: [2] [12] [13]

ImageScientific nameCommon NameDistribution
Thuja koraiensis PAN foliage.JPG Thuja koraiensis NakaiKorean thuja Jilin, Korea
Thuja occidentalis 003.JPG Thuja occidentalis L.eastern arborvitae, northern whitecedarE Canada (Manitoba to Nova Scotia), E United States (primarily Northeast, Great Lakes, Appalachians)
Thuja plicata 43569.JPG Thuja plicata Donn ex D.Donwestern redcedarfrom Alaska to Mendocino County in California
Thuja standishii Brno2.JPG Thuja standishii (Gordon) CarrièreJapanese thuja Honshu, Shikoku
Thuja sutchuenensis (Gordon) CarrièreSichuan thuja Sichuan, Chongqing China almost extinct in the wild

Species formerly placed in Thuja include: [2]

and many more

The extant species Thuja sutchuenensis was believed to be extinct until 1999, when a small population was discovered in southeast China. [14]


Thuja species are used as food plants by the larvae of some Lepidoptera species including autumnal moth, the engrailed and juniper pug. The foliage is also readily eaten by deer, and where deer population density is high, can adversely affect the growth of young trees and the establishment of seedlings. [15]


The genus Thuja has current populations in both North America and East Asia. T. plicata has wide distribution in the Pacific Northwest from Northern California to Alaska, reaching East into Idaho and central British Columbia. T. occidentalis has populations in the Northeastern United States, reaching north into Ontario and Quebec, with some distribution as far south as Tennessee. [16]

T. standishii has populations in mountainous regions of Honshu and Shikoku islands in Japan, with no recorded population in the north of the country. T. koraiensis is native to both North and South Korea and has a small population in the Northern Chinese province of Jilin. [17] The newly rediscovered species T. sutchuenensis has extremely limited distribution in the mountains of Chengkou county in southeastern China.

Evolution and paleobiogeography

Current research suggests that Thuja originated in the Americas and migrated to East Asia via the Bering land bridge in the Miocene. Fossil records show that Thuja was significantly more widely distributed during the late Cretaceous and early Tertiary than we see today. [18] The oldest known Thuja fossil is of T. polaris (an extinct species) from the Paleocene of Ellesmere Island in present-day Nunavut, Canada. [17]

Other hypotheses of Thuja origin involved an East Asian origin, with the genus migrating twice; once east into North-western America and then west to the North-eastern America, but since no reliable fossil records of Thuja exist in either Western Asia or Europe, the possibility can be eliminated. [17]


Thuja is a monophyletic genus that sits within the order Pinales in the Cupressaceae. Thuja is in the Cupressoid clade and is sister to the genus Thujopsis. The sister relationship between Thuja and Thujopsis is supported with 100% bootstrap support and 1.0 posterior probability. [19]

Within the genus the taxonomy is in flux, but most recent research based on molecular analysis of plastomes in the genus Thuja showed evidence for a new grouping, with two sister clades: T. standishii and T. koraiensis together and T. occidentalis and T. sutchuenensis together, with T. plicata sister to T. occidentails and T. sutchuenensis. [19] This newest grouping is hypothesized to be the result of reticulate evolution and hybridization within the genus.

Uses of thuja

They are widely grown as ornamental trees, and extensively used for hedges. A number of cultivars are grown and used in landscapes. [20] [21] Homeowners will sometimes plant them as privacy trees. The cultivar 'Green Giant' is popular as a very vigorous hedging plant, growing up to 80 cm/year when young. [22]

Thuya (MHNT) Thuya coupe MHNT.jpg
Thuya (MHNT)

The wood is light, soft and aromatic. It can be easily split and resists decay. The wood has been used for many applications from making chests that repel moths to shingles. Thuja poles are also often used to make fence posts and rails. The wood of Thuja plicata is commonly used for guitar sound boards. [23] Its combination of light weight and resistance to decay has also led to T. plicata being widely used for the construction of bee hives. [24]

T. plicata is an important tree to the First Nations people of the Pacific Northwest and is sometimes called "Canoe Tree" because of its use as a material for Native American canoes.[ citation needed ]

Oil of Thuja contains the terpene thujone which has been studied for its GABA receptor antagonizing effects, with potentially lethal properties. [25] Cedarwood oil and cedar leaf oil, which are derived from Thuja occidentalis, have different properties and uses. [26]

The natives of Canada used the scaled leaves of Thuja occidentalis to make a tea that has been shown to contain 50 mg of vitamin C per 100 grams; this helped prevent and treat scurvy. [27]

In the 19th century, Thuja was commonly used as an externally applied tincture or ointment for the treatment of warts, ringworm and thrush, [28] and a local injection of the tincture was used for treating venereal warts. [29]

A 2017 trial showed that its extract effectively killed both gram-positive and gram-negative bacteria. [30]

As with many Cupressaceae, Thuja can induce allergic reactions, including skin, eye and breathing problems.[ citation needed ]

Related Research Articles

<i>Cedrus</i> Genus of plants (coniferous trees)

Cedrus, with the common English name cedar, is a genus of coniferous trees in the plant family Pinaceae. They are native to the mountains of the western Himalayas and the Mediterranean region, occurring at altitudes of 1,500–3,200 m in the Himalayas and 1,000–2,200 m in the Mediterranean.

Cypress is a common name for various coniferous trees or shrubs of northern temperate regions that belong to the family Cupressaceae. The word cypress is derived from Old French cipres, which was imported from Latin cypressus, the latinisation of the Greek κυπάρισσος (kyparissos). Cypress trees are a large classification of conifers, encompassing the trees and shrubs from the cypress family (Cupressaceae) and many others with the word cypress in their common name. Many cypress trees have needle-like, evergreen foliage and acorn-like seed cones.

<span class="mw-page-title-main">Cupressaceae</span> Cypress family of conifers

Cupressaceae is a conifer family, the cypress, with worldwide distribution. The family includes 27–30 genera, which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioecious or (rarely) dioecious trees and shrubs up to 116 m (381 ft) tall. The bark of mature trees is commonly orange- to red-brown and of stringy texture, often flaking or peeling in vertical strips, but smooth, scaly or hard and square-cracked in some species.

<i>Cupressus</i> Several genera of evergreen conifers

Cupressus is one of several genera of evergreen conifers within the family Cupressaceae that have the common name cypress; for the others, see cypress. It is considered a polyphyletic group. Based on genetic and morphological analysis, the genus Cupressus is found in the subfamily Cupressoideae. The common name "cypress" comes via the Old French cipres from the Latin cyparissus, which is the latinisation of the Greek κυπάρισσος (kypárissos).

<i>Callitropsis nootkatensis</i> Species of conifer

Callitropsis nootkatensis, formerly known as Cupressus nootkatensis, is a species of tree in the cypress family native to the coastal regions of northwestern North America. This species goes by many common names including: Nootka cypress, yellow cypress, Alaska cypress, Nootka cedar, yellow cedar, Alaska cedar, and Alaska yellow cedar. The specific epithet nootkatensis is derived from its discovery by Europeans on the lands of a First Nation of Canada, the Nuu-chah-nulth people of Vancouver Island, British Columbia, who were formerly referred to as the Nootka.

<i>Thuja plicata</i> Species of conifer

Thuja plicata is a large evergreen coniferous tree in the family Cupressaceae, native to the Pacific Northwest of North America. Its common name is western redcedar in the U.S. or western red cedar in the UK, and it is also called pacific red cedar, giant arborvitae, western arborvitae, just cedar, giant cedar, or shinglewood. It is not a true cedar of the genus Cedrus. T. plicata is the largest species in the genus Thuja, growing up to 70 metres (230 ft) tall and 7 metres (23 ft) in diameter. It mostly grows in areas that experience a mild climate with plentiful rainfall, although it is sometimes present in drier areas on sites where water is available year-round, such as wet valley bottoms and mountain streamsides. The species is shade-tolerant and able to establish in forest understories and is thus considered a climax species. It is a very long-lived tree, with some specimens reaching ages of well over 1,000 years.

<i>Thuja occidentalis</i> Species of evergreen coniferous tree

Thuja occidentalis, also known as northern white-cedar, eastern white-cedar, or arborvitae, is an evergreen coniferous tree, in the cypress family Cupressaceae, which is native to eastern Canada and much of the north-central and northeastern United States. It is widely cultivated as an ornamental plant. It is not to be confused with Juniperus virginiana.

<i>Platycladus</i> Genus of conifers

Platycladus is a monotypic genus of evergreen coniferous trees in the cypress family Cupressaceae, containing only one species, Platycladus orientalis, also known as Chinese thuja, Oriental arborvitae, Chinese arborvitae, biota or Oriental thuja. It is native to northeastern parts of East Asia and North Asia, but is also now naturalised as an introduced species in other regions of the Asian continent.

<i>Calocedrus</i> Genus of conifer trees

Calocedrus, the incense cedar, is a genus of coniferous trees in the cypress family Cupressaceae first described as a genus in 1873. Three species are native to eastern Asia and one to western North America.

<i>Thujopsis</i> Genus of conifers

Thujopsis is a genus of conifers in the cypress family (Cupressaceae), the sole member of which is Thujopsis dolabrata. It is endemic to Japan, where it is named asunaro (あすなろ). It is similar to the closely related genus Thuja (arborvitae), differing in the broader, thicker leaves and thick cones.

<i>Cunninghamia</i> Genus of conifers

Cunninghamia is a genus of one or two living species of evergreen coniferous trees in the cypress family Cupressaceae. They are native to China, northern Vietnam and Laos, and perhaps also Cambodia. They may reach 50 m (160 ft) in height. In vernacular use, it is most often known as Cunninghamia, but is also sometimes called "China-fir". The genus name Cunninghamia honours Dr. James Cunningham, a British doctor who introduced this species into cultivation in 1702 and botanist Allan Cunningham.

<i>Actinostrobus</i> Genus of conifers

Actinostrobus is a genus of coniferous trees in the Cupressaceae. Common names include cypress, sandplain-cypress and cypress-pine, the last of these shared by the closely related genus Callitris.

<i>Microbiota decussata</i> Species of plant

Microbiota is a monotypic genus of evergreen coniferous shrubs in the cypress family Cupressaceae, containing only one species, Microbiota decussata. The plant is native and endemic to a limited area of the Sikhote-Alin mountains in Primorskiy Krai in the Russian Far East. Microbiota is not to be confused with the range of microorganisms of the same name. The genus name was derived from micro-, meaning "small", + Biota, the genus name for a closely related conifer, a species formerly called Biota orientalis, now renamed Platycladus orientalis.

<i>Tetraclinis</i> Genus of conifers

Tetraclinis is a genus of evergreen coniferous trees in the cypress family Cupressaceae, containing only one species, Tetraclinis articulata, also known as Thuja articulata, sandarac, sandarac tree or Barbary thuja, endemic to the western Mediterranean region.

<i>Austrocedrus</i> Species of plant

Austrocedrus is a genus of conifer belonging to the cypress family (Cupressaceae). It has only one species, Austrocedrus chilensis, native to the Valdivian temperate rain forests and the adjacent drier steppe-forests of central-southern Chile and western Argentina from 33°S to 44°S latitude. It is known in its native area as ciprés de la cordillera or cordilleran cypress, and elsewhere by the scientific name as Austrocedrus, or sometimes as Chilean incense-cedar or Chilean cedar. The generic name means "southern cedar".

<i>Diselma</i> Genus of conifers

Diselma archeri is a species of plant of the family Cupressaceae and the sole species in the genus Diselma. It is endemic to the alpine regions of Tasmania's southwest and Central Highlands, on the western coast ranges and Lake St. Clair. It is a monotypic genus restricted to high altitude rainforest and moist alpine heathland. Its distribution mirrors very closely that of other endemic Tasmanian conifers Microcachrys tetragona and Pherosphaera hookeriana.

<i>Juniperus occidentalis</i> Species of tree in North America

Juniperus occidentalis, known as the western juniper, is a shrub or tree native to the Western United States, growing in mountains at altitudes of 800–3,000 meters (2,600–9,800 ft) and rarely down to 100 m (330 ft). It is listed as Least Concern on the IUCN Red List because it is a widespread species with an increasing population.

Thuja sutchuenensis, the Sichuan thuja, is a species of Thuja, an evergreen coniferous tree in the cypress family Cupressaceae. It is native to China, where it is an endangered local endemic in Chengkou County, on the southern slope of the Daba Mountains.

<span class="mw-page-title-main">Thujaplicin</span> Chemical compound

Thujaplicins are a series of tropolone-related chemical substances that have been isolated from the softwoods of the trees of Cupressaceae family. These compounds are known for their antibacterial, antifungal, and antioxidant properties. They were the first natural tropolones to be made synthetically.

<span class="mw-page-title-main">Hinokitiol</span> Chemical compound

Hinokitiol (β-thujaplicin) is a natural monoterpenoid found in the wood of trees in the family Cupressaceae. It is a tropolone derivative and one of the thujaplicins. Hinokitiol is used in oral and skin care products, and is a food additive used in Japan.


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