Thuja Bonsai Care

There are a number of different types of Thuja but as I own a Thuja Plicata, This care guide will be more aimed towards these, although the basic principles should apply to any type of Thuja.

Thuja Plicata is a tall, ever green coniferous tree commonly know as the Western Red Cedar, Pacific Red Cedar, Western Arborvitae or the Giant Cedar.

Although it is called a Cedar, it is not actually a Cedar.

In the summer of 2016 I cleared out my overgrown communal garden, and under the brambles I found a Thuja Plicata. I air layered the top off and I’ve had it ever since. You can see its development in my Thuja Bonsai Progression.

What Is The Natural Habitat of A Thuja?

Thuja Plicata is native to the North American, in particular the Pacific North West region. This should give you an idea of what type of conditions it likes growing in.

What Soil Do Thuja Bonsai Need?

Thuja bonsai prefer a moist, well draining soil. I use my standard mix of equal parts Perlite/Molar Clay/Compost and have not had any trouble with this.

So long as you soil is not holding a lot of water, the tree should be happy.

(For more info on soil read – A General Guide To Bonsai Soil)

How Do you Water A Thuja Bonsai?

Thuja bonsai enjoy plenty of water, but do not like to be sat in water, so well a draining soil is needed. This will allow you to water often, while not allowing things to get waterlogged.

You should also water your tree just before it dries out so that it can remain moist at all times.

(For more info you can read –How To Water A Bonsai)

How Much Sun Light Does A Thuja Bonsai Need?

Thuja bonsai trees can take full sun. They grow pretty tall in nature, so they are not used to being shaded out.

The more light you can give them, the happier they will be.

How Hardy Are Thuja Bonsai?

Thuja trees are fully hardy in the U.K and can handle temperatures as low as -20°C/68°F when grown in the ground.

If you are growing in a bonsai pot, it will still be able to handle very low temperatures, but may need some protection if you are getting close to the -20°C/68°F region. If you are somewhere where it gets this low for an extended period of time you should put the tree in an unheated shed or greenhouse to take the edge off the cold.

(For more info you can read – Working Out How To Over Winter Bonsai Trees)

How Often Do You Feed A Thuja Bonsai?

I feed my Thuja bonsai once a month during the growing season with a general all purpose fertiliser which is more than enough to keep them growing healthily.

(For more info you can read – Do You Need To Use “Bonsai” Fertiliser?)

How Do Thuja Bonsai Respond to Pruning?

Thuja are often used as hedges and respond well to pruning. You should not fully strip a branch of foliage as it will die, so long as there is always some green on a branch, it should be fine.

Thuja can take more pruning than most conifers, but you should still be cautious and not prune too much off at once. You can slowly reduce things over a number of pruning sessions.

(For more info you can read- How To Prune A Bonsai Tree)

Repotting A Thuja Bonsai

Thuja bonsai should be repotted in spring.

I have been careful with the amount of roots I have removed, Most evergreen trees like this are not keen on heavy root pruning. Just be cautious and you should be fine. It will take you a number of years to sort out the roots and get them under control.

(For more info you can read – How To Repot A Bonsai Tree)

Wiring A Thuja Bonsai

Thuja bonsai will need wired to give them a style. They naturally grow upwards and if you leave them in the ground they will end up a large conical shape, while this is fine, it is not ideal for bonsai.

You will find styling them using wire is going to be more effective than trying to only use clip and grow techniques.

(For more info read – Why Do We Wire Bonsai?)

What Is The Leaf Pattern Of A Thuja Bonsai?

The leaves of a thuja are flat scale like sprays of foliage.

What Pests Does A Thuja Bonsai Suffer From?

Scale insects and aphids can attack a Thuja bonsai. If your tree is growing well and healthy, the pests should leave it alone.

You should still check for pests regularly and deal with the quickly if you find them. The sooner you get rid of them the less likely your tree is going to suffer.

Can You Propagate A Thuja Bonsai?

Thuja bonsai can be propagated easily from air layers. They can also be rooted from cuttings.

What Is The Growth Rate Of A Thuja Bonsai?

Thuja bonsai grow quite quickly especially when young. The trees can easily reach 35m tall when grown in the ground, so a young tree will have lots of energy to grow.

This will be a lot slower in a pot, but given the right conditions you will see fast growth. Often you will get a lot of long shoots, which are pretty useless for bonsai, but you can just remove these.

Should You Get A Thuja Bonsai?

Thuja bonsai are not ideal for beginners. Although they are low maintenance when used as hedges they need to be given special care when being pruned and shaped for bonsai.

They can be quite tricky to style and to keep small. They are always going to want to grow big, so it is a challenge to tame them and keep control of them.

You can read more about if Thuja Are Good Trees For Bonsai.