Red cedar

Red cedar tree
Red cedar tree

Red cedar, also called western red cedar, is the species Thuja plicata. It should not be confused with the eastern red cedar, Juniperus virginiana, or the Lebanon cedar, Cedrus libani, which are unrelated species. Eastern red cedar is toxic if taken internally.

Western red cedar is a tree that grows to a height of 125 ft (60 m) in moist soils in mixed coniferous forests. It has red-brown or gray-brown bark with thick longitudinal fissures that is easily peeled. Its foliage develops in sprays about 6 in (15 cm) long with small, highly aromatic leaves. The leaves, twigs, bark, and roots are all used medicinally.

Western red cedar is found in the western United States and western Canada from Alaska through northern California and in the Rocky Mountains from British Columbia through Montana.

Other names for Thuja plicata include giant red cedar, giant arborvitae, shinglewood, and canoe cedar. It is one of the most commercially important logging trees in the western United States.

A relative of the western red cedar, Thuja orientalis, grows in the eastern part of the United States and Canada. The naming of this species is confusing. It is called yellow cedar, but is sometimes also called arbor vitae.

Confusingly, another relative, Chinese arbor vitae, is referred to in literature as interchangeably as Biota orientalis and Thuja orientalis. It is used in traditional Chinese medicine in many of the same ways as Thuja plicata.

General use

Red cedar leaf
Red cedar leaf

Red cedar is of major cultural importance to Native American tribes living in the Pacific Northwest. The wood, bark, limbs, and roots were used to provide many of the needs of the tribe ranging from shelter to cooking implements to medicine.

Red cedar also has spiritual significance to some of these tribes and is used in ritual ways. Red cedar was a major medicinal herb for these Pacific Northwest cultures, although it is not much used today.

Native American tribes used the twigs, leaves, roots, bark, and leaf buds of red cedar to treat many different symptoms. Internal uses include:
  • boiling limbs to make a tuberculosis treatment
  • chewing leaf buds for sore lungs
  • boiling leaves to make a cough remedy
  • making a decoction of leaves to treat colds
  • chewing leaf buds to relieve toothache pain
  • making an infusion to treat stomach pain and diarrhea
  • chewing the inner bark of a small tree to bring about delayed menstruation
  • making a bark infusion to treat kidney complaints
  • making an infusion of the seeds to treat fever
  • using a weak infusion internally to treat rheumatism and arthritis

External uses include:
  • making a decoction of leaves to treat rheumatism
  • washing with an infusion of twigs to treat venereal disease, including the human papilloma virus and other sexually transmitted diseases
  • making a poultice of boughs or oil to treat rheumatism
  • making a poultice of boughs or oil to threat bronchitis
  • making a poultice or oil from inner bark to treat skin diseases, including topical fungal infections and warts
  • using shredded bark to cauterize and bind wounds

Scientific research supports some of these traditional uses of red cedar. Extracts of red cedar have been shown to have antibacterial properties against common bacteria. Compounds with antifungal properties have also been isolated.


Red cedar cones
Red cedar cones

Most preparations of red cedar call for boiling the medicinal parts to make a decoction or for making a tea or infusion. Little information exists on dosages.

An essential oil can be prepared from red cedar. This oil is meant to be used topically. It is toxic if taken internally, and has the ability to produce convulsions or even death if taken in even small quantities.

A 1999 study done in Switzerland noted an increase in poisoning deaths from plant products, including Thuja, due possibly to an increase in people practicing herbal healing and aromatherapy.


As noted above, the oil of all species of thuja can cause convulsions. Decoctions of the bark of red cedar can also cause miscarriage. Therefore, pregnant women should not use red cedar.

Side effects

Red cedar fruit
Red cedar fruit

Many people develop asthma and bronchial spasms from exposure to red cedar or red cedar dust. This is due to an allergic reaction to plicatic acid present in the wood.

Red cedar induced asthma is a serious occupational hazard to loggers in western North America. Estimates of the number of loggers who develop occupational asthma due to red cedar exposure range from 4-13.5%.


There are no studies and little observational evidence to indicate whether red cedar interacts with other herbs or with Western pharmaceuticals.