Arborvitae Root System

Arborvitae Root System

Introduction to Arborvitae

Arborvitae (genus Thuja) are coniferous trees belonging to the Cupressaceae (cypress) family and since ancient times it has been a mythological symbol of immortality and life within the cosmos. This monophyletic genus of five species, two, native to North America and three, native to eastern Asia, consists of the resinous, evergreen ornamental members that are commonly known as Arborvitaes, cedars or thujas. During the 16th century, the French explorer Jacques Cartier learned that scurvy, a disease caused due to a deficiency of vitamin C could be cured by boiling the leaves and the bark from the plant, the Native Americans called “Arborvitae”. Ever since then the Arborvitae plant became widely known by the French as “l’arbre de vie” or “tree of life”. Today the nickname, “tree of life”, extends well beyond the thuja’s ability to cure diseases and may be attributed to the tree’s tendency to resist rot and live up to almost 800 years. The two North American natives, that is, the Thuja occidentalis (American or eastern arborvitae or northern white cedar) and the Thuja plicata (giant arborvitae or western red cedar) are the most commonly known types. The other three species, native to eastern Asia are Thuja koraiensis (Korean thuja), Thuja standishii (Japanese thuja) and Thuja sutchuenensis (Sichuan thuja).

The physical features of the evergreen conifers are interesting, the tree is very durable with its narrowly conical to broadly pyramidal shape. The flattened foliage, resembling scales or fan-like sprays are bright green throughout the spring, turning yellowish-green or brownish-green during the late autumn and winters. The spiky leaves when crushed give off a spicy odour, which some happen to call nature’s perfume. Homeowners love the aroma of arborvitae.

Arborvitae is a common household ornamental plant used today for picturesque garden designs and very commonly used as screening hedges or living fences when planted in rows, given their dense foliage. They are easy to grow and require little care and maintenance. During the winter season when supplies get low, some animals like deer turn to the arborvitae for their survival.

Scientific Classification

Kingdom: Plantae

Clade: Tracheophytes

Division: Pinophyta

Class: Pinopsida

Order: Pinales

Family: Cupressaceae

Subfamily: Cupressoideae

Genus: Thuja

Plant Specifications

Plant specification of Arborvitae

  • Arborvitaes are trees or shrubs with a conical or pyramidal shape.
  • They have a scaly outer bark and a fibrous inner bark.
  • These cedars have horizontal branches with a flattened-out, fan-like branchlet system.
  • The male and female reproductive structures (cones) sprout from different branchlets of the
    same tree.
  • The male cones are rounded and reddish or yellowish in colour.
  • The female cones are smaller in size and green in colour, possibly with a tinge of purple.
  • Mature cones are egg-like in shape and may grow up to half an inch long with thickened flexible scales.
  • Arborvitae wood is soft and light in weight, yet very durable and therefore easily worked making them very important as a timber-producing species.
  • Plant size may vary, depending on species type, but range from shrubs as small as 3 feet in size to gigantic trees over 70 feet tall with widths of up to 25 feet.

Root System of Arborvitae

Root System of Arborvitae

  • Arborvitaes have a shallow, fibrous root system and this root system may spread to the edges of the dripline, which is the outer most circumference of the tree’s canopy. The roots of small arborvitae may reach depths of up to 8 inches while the roots of larger arborvitae may extend to depths of 18-24 inches.
  • Arborvitaes are able to grow in many soil types; however, waterlogging and root competition may pose serious problems to their growth. The soil must be well-drained with a minimal amount of clay and sand so the roots may spread with adequate room to grow.
  • It is important to leave at least 3-4 feet between the plants if planting them in a row, as one may do in the case of growing a hedge fence. Cultivators are often advised to place their arborvitaes in holes dug an inch less than the depth of the root ball but three times as wide so that the roots have adequate room to spread and that is because these roots grow in a manner so as to spread as horizontally wide as possible since they do not dig very deep into the soil.

Root Rot

Root Rot

Root rot is a common concern amongst arborvitae cultivators and common causes of root rot may be attributed to water-logging, excessive heat or snow-cold conditions or pathogens such as phytophthora. These conditions vary in different species, for example, the western red cedar (Thuja plicata) is most resistant, while the northern white cedar (Thuja occidentalis) is the most susceptible to phytophthora.

Cause of Root Rot

Over-watering is one of the most common causes of root rot and fungal infection, which may lead to irreversible damage and may be indicated by a yellowing or browning foliage with drooping needles, and therefore as a simple rule of thumb, newly planted shrubs should be watered with an inch of water, once a week, during the growing season, but should not be saturated.

Arborvitae rarely ever needs fertilization if planted in good soil and if given enough water and sunlight. However, if the soil is less than adequate, the plant may require a nutritional boost and therefore it may be imperative to note that a slow-release granular fertilizer, watered well after each application would work best and would avoiding root burn.

Despite these concerns, arborvitae is a tolerant plant and can still grow in clay and sand given adequate water drainage and room for the root growth. They require bright sunlight but have been known to grow in shady climates as well. They are a strong plant that can survive extremes and while they are easy to maintain, they would still appreciate all the care they can get, in order to give the evergreen and dense foliage so desired by the cultivator.

Arborvitae Care and Pruning

Arborvitae care and pruning

Arborvitaes are ornamental garden plants that may add a sophisticated entry to someone’s home or stand as a statuesque specimen in the centre of their lawns. They may be pruned into many designs giving any garden a lush green and bushy attire, adding to the aesthetics of that garden. Arborvitaes can withstand frequent and heavy pruning if they are to be shaped into formal hedges or topiaries but since they can retain their shape as they mature, regular pruning is usually not necessary.

Here are a few tips on how to care for arborvitae when pruning:

  • Light pruning in early growth will keep them neat and encourage thicker growth. Do not cut back to bare wood.
  • Cutting off the top of the plant to control its height or trimming branch tips will permanently affect the plant leaving no room for new growth. Selective pruning of the leaf blades is encouraged to shorten the height.
  • It is important to maintain a thicker bottom. Pruning to achieve a V-shape will yellow or brown the lower branches leaving the foliage sparse.
  • Allow new growth to fill gaps before getting rid of dead or diseased branches.
  • Encourage air circulation by removing accumulated dead foliage inside the plant frequently.
  • In areas with a deer population arborvitae may require a mesh net protection during the winter season.

Uses of Arborvitae

Arborvitae uses

Medicinal uses

  • Arborvitae is useful in treating respiratory illnesses such as common cold, sinusitis and even bronchitis.
  • It is used to treat arthritis and reduce pain from sore muscles or injuries.
  • Arborvitae is also used to treat skin infections such as warts or cold sores.
  • Arborvitae contains the neurotoxin thujone, which can be toxic when consumed in large doses and it has been advised that pregnant women avoid the consumption of arborvitae products as it may risk a miscarriage.
  • The leaves of Eastern white cedar are used to make a tea which contains 50 mg of vitamin-C per 100 grams. This helps treat scurvy.

Commercial uses

  • Arborvitae is widely known as ornamental trees and is extensively used for hedges or as fences.
  • Arborvitae wood is used in timber production because of its durability and resistance to decay.
  • The oil from Arborvitae can be used as a cleansing and purifying agent. Arborvitae oil can also be used as wood polish keeping furniture looking fresh for a longer time.
  • Arborvitae is a powerful disinfectant against insect damage and is used to prevent decay in wood, whether in storage, construction or furniture.
  • Arborvitae is also used in cosmetics for its invigorating aroma that brings on a sense of calm and peace.
  • The wood of arborvitae is also commonly used for making guitar soundboards.
  • Arborvitae wood is used in the construction of beehives because of its combination of light weight and resistance to decay.
  • Arborvitae is also known as the “canoe tree” because it is used for making native American canoes.

Interesting Facts About Arborvitae

Arborvitae interesting facts

  • Arborvitae is a drought-resistant tree.
  • The arborvitae is a privacy tree because of its dense foliage and it can provide year-round privacy and shade when placed strategically.
  • The aromatic branches of the arborvitae are a big part of New Year’s celebrations in China and are considered good luck charms.
  • Arborvitaes are one of the evergreen conifers preferred as a Christmas tree.


  1. Laura
  2. Lawrence Maiolo
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