The bark is harvested by indigenous peoples and processed into a fiber, which they use to make items such as rope, baskets, clothing, and rain hats.

[18] Basic and animal studies have shown that thujaplicins may have other biological properties, including antibacterial, antiviral, and antioxidant activities,[19] however reliable evidence on their effectiveness is still lacking.

[25] Pollen Assemblages at Seeley Lake, on the eastern slope of the Coast Mountains east of Haida Gwaii, indicate that western redcedar became common there at approximately 2,200 YBP.

[26] The species name plicata derives from the Latin word plicāre and means 'folded in plaits' or 'braided,' a reference to the pattern of its small leaves.

[5] The easternmost extent of its distribution occurs in Glacier National Park in Montana, where it is a major component of forests surrounding Lake McDonald.

[29] It is present on all landforms and soil classes on Vancouver Island,[29] but is restricted to wet, low-lying areas and streamsides in the drier eastern portions of its range.

[38] Western redcedar is less cold-tolerant than many conifer species that it shares its range with and is vulnerable to frost damage in late spring and early fall.

[41] The species was described as invasive in Great Britain by a 2004 survey,[42] although it is not listed as such by the United Kingdom Department for Environment, Food and Rural Affairs under the Wildlife and Countryside Act 1981 as of September 2022.

[30] Pileated woodpeckers on the Olympic Peninsula prefer very large western redcedars with heart rot when selecting roosting sites, but do not use them for nesting, instead relying on Pacific silver fir (Abies amabilis) for that purpose.

[46] The foliage, especially that of saplings, is an important food source year-round for browsing ungulates such as Roosevelt elk and black-tailed deer, especially during the winter months when little else is available.

[47] The seeds may be eaten by birds and rodents such as deer mice, but are apparently not the preferred food source for most species, possibly due to their small size or unpleasant odor.

The study also found that western redcedars do not increase their growth rates in response to canopy gap formation that occurs after the death of a mature overstory tree as much as the two other species.

Another type of forest characterized by dense stands of western hemlock and Pacific silver fir with sparse understory vegetation also occurs in the area.

The two forest types occur in areas with very similar environmental conditions and are separated by sharp boundaries, often less than 10 metres (33 ft) wide.

[30] Western redcedar shows susceptibility of varying degrees to the following soil pathogens: Armillaria ostoyae, Fomitopsis pinicola, Heterobasidion annosum, Phaeolus schweinitzii, Phellinus weirii, Rhizinia undulata, and Postia sericeomollis.

[57] Studies have found that western redcedar produces a phytochemical called thujaplicin which has been credited with granting the species its natural resistance to fungal attacks.

[58] Because of these natural defenses, it has been suggested that western redcedar may serve as a suitable alternative to other conifers when regenerating a site affected by these pathogens.

[60] A study published in 2013 projected a decrease in the incidence of cedar leaf blight among western redcedars in coastal British Columbia by late 21st century as a result of warmer, drier summers due to climate change.

They hypothesized that warmer winter temperatures could result in increased incidence of cedar leaf blight and cautioned that management decisions should take this uncertainty into account.

"[65] Like its relative Thuja occidentalis and many other conifer species, T. plicata is grown as an ornamental tree, and for screens and hedges, throughout the world in gardens and parks.

[66] The following cultivars have gained the Royal Horticultural Society's Award of Garden Merit: Western redcedar is considered the Tree of Life by many of the First Nations of the Pacific Northwest, as the tree gave them everything that they needed for life: food, water (in the form of water tight woven cedar bark baskets), clothing, medicine, transportation (their canoes made from the wood), shelter (boards of wood used to build their long houses), and spirituality (the boughs being used in many ceremonies).

[72][page needed] Some northwest coast tribes refer to themselves as "people of the Red Cedar" because of their extensive dependence on the tree for basic materials.

Woodworking tools dating between 8,000 and 5,000 years ago, such as carved antlers, were discovered in shell middens at the Glenrose site, near Vancouver, British Columbia.

[75] The Musqueam site, also near Vancouver, yielded bark baskets woven in five different styles, along with ropes and ships dated to 3,000 years ago.

Some theories include shipwrecks from East Asia or possible contact with iron-using cultures from Siberia, as hinted in the more advanced woodworking found in northern tribes such as the Tlingit.

[85] Redcedar wood is used to make huge monoxyla canoes in which the men went out to high sea to harpoon whales and conduct trade.

He gave her the name of Tilikum ('Relative' in Chinook jargon), rigged her, and led her in a hectic three-year voyage from British Columbia to London.

It is valued for its distinct appearance, aroma, and its high natural resistance to decay, being extensively used for outdoor construction in the form of posts, decking, shingles, and siding.

The US Occupational Safety and Health Administration has set a permissible exposure limit for western redcedar dust of 2.5 mg/m3 as a time-weighted average over eight hours.

Located near the northwest shore of Lake Quinault north of Aberdeen, Washington, about 34 kilometres (21 mi) from the Pacific Ocean, it was one-third the volume of the largest known tree, a giant sequoia named 'General Sherman'.