Root Rot in Cedars in Western Canada


The mild, temperate climate of western Canada, principally British Columbia, is an ideal setting for the majestic western redcedar, a towering tree held in reverence by aboriginal cultures for centuries. Redcedars thrive in the hemlock forests of British Columbia and into southwestern Alberta and along with yellow cedars are an important part of British Columbia's logging industry. Mature trees are naturally resistant to disease, including root rot, and are rarely killed by it.

Western Cedar History

Yellow cedars and redcedars (Chamaecyparis nootkatensis and Thuja plicata) are not true cedars, but cypress. Botanists combine the name to redcedar to indicate this, but general usage often separates the words. Used and revered by the Pacific coast aboriginal cultures for centuries, redcedars grow to 210 feet with a trunk of 12 feet, with flat feathery leaves; they live for centuries. Yellow cedars grow to 75 feet with drooping branches and blue-green leaves. They grow in areas of high humidity and tolerate low light. Redcedars have a wider range. Called the "Life Giver" by Pacific northwest tribes, aromatic western redcedar bark, limbs, roots and wood were used for rope, baskets, clothes, canoes, totem poles, medicines and masks for centuries. The straight, decay- and weather-resistant wood of both cedars is prized for home building, furniture, shingles, siding, boats and decks.

Western Cedar Characteristics

Western redcedars are known to live 1,460 years. For centuries, the coastal native cultures like the Lummi, Cowlitz, Skagit and Skokomish chewed or drank tea from the buds, bark and leaves to cure sore throats, toothache, sore lungs, coughs, kidney trouble and even tuberculosis and venereal diseases. Aboriginal cultures used the yellow cedar along the coastline for paddles, dishes, bows and masks, and wove the bark into blankets and clothes.

Yellow and Redcedar Resistance

Mature yellow and redcedars produce the chemical thujaplicin, which gives it its characteristic aroma. It is also a natural fungicide that resists rot. Thujaplicin is powerful enough to last a century after the tree has fallen and been turned into building materials. Saplings don't produce the chemical and can rot at an early stage. They continue to grow, but have a hollow, rotting trunk

Types of Root Rot

The main forms of rot that attack western cedars are brown cubical butt and pocket rot and the cedar form of laminated root rot. Cedar pocket rot is the second most common form of decay in redcedars. Most old-growth yellow and redcedars have some degree of butt rot, which weakens the tree and causes breakage low on the trunk.The culprit is Laminated Root Rot (P. weirii), which moves up the trunk as it splits and weakens the wood. Other fungi that invade yellow and redcedars less often include armillaria root rot and annosus root and butt rot. Rhizina root rot attacks and kills redcedar seedlings and mature trees up to two years after a fire. Schweinitzii butt rot and Tomentosus root rot rarely invade western cedars.

Root Rot Damage

Yellow and redcedars can live with laminated root rot; in fact, most mature trees have it to some degree. It degrades the value of the wood and affects British Columbia's lumber industry. While less common, armillaria will kill trees while annosus kills young trees quickly and very large trees after a few years. There is no cure.

Keywords: redcedar root rot, yellow cedar diseases, growing western cedars

About this Author

TS Owen spent her career in journalism, winning the national Koop science writer award and penning articles in "Newsweek" and the "San Francisco Chronicle." She also served as an editor for a variety of publications in the San Francisco Bay Area and Banff, Alberta. Owen has a master's degree in English education.