This genus of six species of evergreen coniferous trees occurs in E Asia and N America. Thuja occidentalis and T orientalis are widely grown as ornamentals; both have numerous cultivars, varying in size, habit and color, making them some of the most versatile conifers for garden use. Thujas have aromatic foliage, rich in volatile oil, which consists mainly of thujone, a toxic compound also found in Artemisia absinthium (See, Wormwood). Thuja occidentalis has long been used by native N Americans, providing materials for bows, canoes, baskets, cordage, and roofing, and medicines to treat menstrual problems, headache, and heart disease. It was made into anti-rheumatic tea by loggers in the wetland forests where it grows wild, and listed in the U.S. Pharmacopoeia (1882-94) as a uterine stimulant and diuretic. Thuja orientalis was first described in Chinese medicine in the Tang Materia Medica (c.CE569). Some botanists now classify this species as Platycladus orientalis.

Cedar leaf's scientific name, Thuja, comes from the Greek thuo, which means "to sacrifice" and alludes to the Greek practice of burning the fragrant cedar wood when making sacrifices. The aromatic cedar leaf oil has been used for respiratory, menstrual, and urinary problems; rheumatism; psoriasis; and wart removal. It has also been used as an antifungal agent for ringworm and thrush. Cedar leaf's major constituent, thujone, is toxic in large doses, so long-term use should be avoided.

Slow-growing, narrow conifer with orange-brown bark and tiny, scale-like leaves, that turn bronze in winter and have an apple scent when crushed. Flowers consist of minute black male cones and erect yellow-green, ovoid female cones, 1cm (½in) long, that turn brown and pendulous when ripe.

Common Name:
Other Names:
American Arbor Vitae, Arbor-Vitae, Cedar Leaf, Eastern White Cedar, Swamp Cedar, Thuja, Tree of Life, Yellow Cedar
Botanical Name:
Thuja occidentalis
Native Location:
Eastern N America
Deep, moist, well-drained soil in sun. Dislikes cold, drying winds when young. Trim hedges in spring and late summer. Trees may be damaged by scale insects, aphids, canker, and Keithia disease.
By seed sown in late winter (species only); by semi-ripe cuttings in late summer.
Foliage and bark are removed as required and dried for use in decoctions, liquid extracts, and tinctures. Seeds (T. orientalis) are collected from ripe cones in autumn and dried for use in decoctions, powders, and tinctures.
Is dense and conical tree with rich green foliage, held vertically.
Height: 3-4m (10-12ft)
Has old-gold foliage, pinkish when young, which bronzes in winter.
Height: 1-2m (3-6ft)
Is compact and dwarf, with bright green foliage.
Height: 1m (3ft)
Width: 80cm (32in)
10-20m (30-70ft)
3-5m (10-15ft)
Parts Used:
Foliage, bark, leaf, oil of the leaf.
Chemical Constituents
  • Fenchone
  • Pinopicrin
  • Tannins
  • Thujone
  • Volatile Oils
  • Properties:
    A bitter, astringent, cooling herb with a camphoraceous, fruity aroma. It stimulates the heart, uterus and nerves, reduces inflammation, clears toxins, and is diuretic, expectorant, anti-fungal, and anti-viral.
    Medicinal Uses:
    Internally in cancery therapy and for bronchial complaints (especially associated with congestive heart failure), urinary infections (including cystitis), bed-wetting in children, psoriasis, eczema, failure to menstruate. Once used to treat side effects of smallpox vaccinations. Externally for vaginal infections, warts, muscular aches, and rheumatism. Combined with Hamamelis virginia (See, Common Witch Hazel) as a lotion for exudative eczema.
    Tro treat respiratory tract infections, arthritis, bacterial skin infections, and herpes simplex.
    Known Effects:
  • Stimulates central nervous system
  • Stimulates heart muscle to contract more efficiently
  • Destroys intestinal worms
  • Causes uterine contractions
  • Interferes with the absorption of iron and other minerals when taken internally

  • Miscellaneous Information:
    Yellow cedar has caused deaths when misused to induce abortions.
    Possible Additional effects:
  • May relieve muscular aches and pains
  • May treat warts
  • May cause abortions (miscarriages)
  • Warnings and Precautions:
    Leaves are toxic if eaten.
    Skin allergen.
    Contraindicated during pregnancy and in dry, irritant coughs.
    For use by qualified practitioners only.

    Don't take if you:
    Are pregnant, think you may be pregnant, or plan pregnancy in the near future.
    Consult your doctor if you:
  • Take this herb for any medical problem that doesn't improve in 2 weeks (There may be safer, more effective treatments.)
  • Take any medicinal drugs, or herbs including aspirin, laxatives, cold and cough remedies, antacids, vitamins, minerals, amino acids, supplements, other prescription or non-prescription drugs

  • Pregnancy:
    Dangers outweigh any possible benefits. Don't use.
    Dangers outweigh any possible benefits. Don't use.
    Infants and Children:
    Treating infants and children under 2 with any herbal preparation is hazardous.
    Dangers outweigh any possible benefits. Don't use.
  • Store in a cool, dry area away from direct light, but don't freeze
  • Store safely out of reach of children
  • Don't store in bathroom medicine cabinet. Heat and moisture may change the action of the herb

  • Safe Dosage:
    Consult your doctor for the appropriate dose for your condition.
    Typical Dose:
    A typical dose of cedar leaf may range from 2 to 4 ml of liquid extract (no specified concentration).
    Possible Side Effects:
    Cedar leaf's side effects include asthma, seizures, nausea, and painful diarrhea.
    Drug Interactions:
    Taking cedar leaf with these drugs may increase the risk of seizures:
    Acetazolamide,(Apo-Acetazolamide, Diamox Sequels)
    Arbamazepine,(Carbatrol, Tegretol)
    Clonazepam,(Klonopin, Rivotril)
    Clorazepate,(Tranxene, T-Tab)
    Diazepam,(Apo-Diazepam, Valium)
    Gabapentin,(Neurontin, Nu-Gabapentin)
    Lorazepam,(Ativan, Nu-Loraz)
    Oxazepam,(Novoxapam, Serax)
    Phenobarbital,(Luminal Sodium, PMS-Phenobarbital)
    Phenytoin,(Dilantin, Phenytek)
    Primidone,(Apo-Primidone, Mysoline)
    Thiopental (Pentothal),()
    Valproic Acid,(Depacon, Depakote ER)
    Disease Interactions:
    May irrigate the gastrointestinal tract and worsen gastrointestinal ailments.
    Supplement Interactions:
    Increased risk of thujone toxicity when taken with herbs containing thujone, such as Oak Moss, Oriental Arborvitae, Sage, Tansy, Tree Moss, and Wormwood.
    Adverse Reactions, Side Effects or Overdose Symptoms:
    Signs and Symptoms What to do

    Abortion Seek emergency treatment
    Coma Seek emergency treatment
    Convulsions Seek emergency treatment
    Precipitous blood pressure drop: symptoms include faintness, cold sweat, paleness, rapid pulse Seek emergency treatment
    The Encyclopedia of Herbs by Deni Bown Copyright © 1995, 2001 Dorling Kindersley Limited. Pp. 386-387.
    The Essential Herb-Drug-Vitamin Interaction Guide by Geo. T. Grossberg, MD and Barry Fox, PhD Copyright ©2007 Barry Fox,PhD, Pp. 137-138
    Vitamins, Herbs, Minerals & Supplements The Complete Guide By H. Winter Griffith Copyright©1988 Fisher Books pp. 469-470