Canadian thuja (Thuja occidentalis)

The Thuja occidentalis is a very adaptable Conifer, so that you can have as a tree or bush a few meters. As it also remains evergreen, it is a very interesting species so that the garden – or the patio – looks alive every day of the year.

Its growth and development rate is not the fastest in the world, but it is not slow either, which will allow you to control it very easily. Get to know it.

Origin and characteristics

Image – Wikimedia/ Joshua Mayer

It is a tree, or to be more exact a conifer, known as Canadian thuja or western thuja that belongs to the Cupressaceae family. It is native to the northeastern United States and southeastern Canada. It grows to a height of between 10 and 20 meters (maximum 35), with a trunk of up to 40-60cm in diameter.

Its very small leaves, 3-5mm long, green in color. These gradually fall, very slowly, as new ones appear throughout the year. The fruit is a cone that, when ripe, is brown in color, measuring 10-15mm by 4-5mm wide, and contains about 7 seeds.

It has a very long life expectancy, being able to exceed 1000 years. The oldest that has been discovered died at 1,500 years, and lived on South Manitou Island, in Leelanau County, Michigan (United States).


There are several, among which we highlight:

  • Golden Globe: it measures one meter in height, has a dwarf bearing and a spherical shape.
  • Lutescens: its bearing is pyramidal and the leaves are yellowish.
  • Pyramidalis Compacta: its bearing is columnar.
  • Rheingold: its bearing is spherical, and its leaves are yellowish.

What are their cares?

Image – Wikimedia/ Quartl

If you want to have a copy, we recommend you take care of it as follows:


The Thuja occidentalis must be outdoors, in full sun or, failing that, in a bright area. It is not an invasive plant, but its roots need space so it is advisable to have it at a minimum distance of 4-5 meters from the pipes (it does nothing to the walls, walls, etc.; in fact when it is kept as a hedge it is usual that it is planted a few centimeters from these).


  • Garden: grows in soils with good drainage, preferably fertile and deep.
  • Pot: can be filled with universal substrate for plants (on sale here), or if preferred, with mulch (on sale here ) or even a specific one for garden plants (on sale here ) that is richer in nutrients.


It does not resist drought. This is a conifer that needs frequent watering in summer, and somewhat less during the rest of the year. But also, you have to know that excess watering hurts it a lot, to the point that its roots, once they start to rot, are difficult to get ahead. With this in mind, it is important that the soil or substrate drains the water well and quickly, and that the moisture is checked before re-moistening, for example with a thin wooden stick.

Thus, you will see that, depending on the weather, it may need about 3 or 4 weekly waterings during the hottest and dry season, and 1-2 weekly the rest of the year.


From the beginning of spring to the end of summer, it is highly recommended to fertilize yours from Canada with organic fertilizers:

  • If it is in the garden: use mulch, compost, or the like. Spread a layer about 3-4cm thick around the trunk, and water.
  • If it is in a pot: use liquid fertilizers, such as liquid guano for example (on sale here ), following the instructions specified on the package.


It is pruned at the end of winter, removing dry, diseased, weak branches and those that are broken. Take the opportunity to trim those that are growing too much. Use pruning tools previously disinfected with pharmacy rubbing alcohol or a few drops of dishwasher.

When finished, put healing paste on the wounds (on sale here ), in all, but especially in the larger ones (those of more than 0.5cm in diameter).


The Thuja occidentalis is grown from seeds in winter and mid-summer cuttings. How do you proceed in each case? Let’s see it:


The first thing to do is stratify them, that is, to sow them in a tupperware with a sterile substrate (that is, new, unused), previously moistened with water, and then place said container in the refrigerator for three months. Do not forget to remove it once a week and remove the lid so that the air is renewed and thus avoid the appearance of fungus.

Related article:How to stratify seeds step by step

After that time, they are sown in seedbeds (like this one that they sell here ), with cultivation substrate, finally it is placed outside, in semi-shade.

If all goes well, they will germinate throughout the spring.


Twigs of about 15cm long are cut from somewhat hard wood at the base, and then they are put to root in pots with substrate wrapped with plastic (they can be put in transparent plastic bags in which some holes will have been made so that the air can circulate).

To make them more likely to root, it is advisable to impregnate the foundation with liquid rooting hormones (on sale here ).

Planting or transplanting time

In spring, when the risk of frost has passed. If you have it in a pot, transplant it to a larger one every two or three years.


It is quite resistant, but can be affected by:

  • Spider mites: such as Paratetranychus ununguis, which causes desiccation of the leaves. It is treated with an anti-spider insecticide.
  • Barrels: like the Phloeosinus thujae, they make holes in the trunk and branches, causing the general weakening of the plant. It is treated with copper-based insecticides.
  • Mealybugs: they can be cottony or limpet-like, in any case, they feed on the sap of the young shoots and are killed with anti-mealybugs or diatomaceous earth.


You may have the following:

  • Seridium: they are fungi that cause the desiccation of the leaves and the appearance of cankers. It is fought with fungicides.
  • Spring browning: if at the end of winter and/ or early spring the land is frozen but the temperature is high, the leaves turn brown due to the fact that perspiration is more frequent than the provision of water by its root system.
    It is not serious, but it can be watered with somewhat warm water until the earth is completely free of ice.


It resists frosts down to -18ºC, and temperatures up to 40ºC do not harm it too much as long as it has water (but not in excess, as we have said before in Irrigation).

What uses is given to Thuja occidentalis ?

Image – Wikimedia/ Raul654


It is a plant that is used above all as an ornamental, either as an isolated specimen or in groups. It is highly appreciated as a hedge, for its adaptability and rusticity.


The wood from its trunk is used in naval and hydraulic construction.

What did you think of this conifer?

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