Deep green foliage that stays put from midwinter to early winter, dense enough to cut off the view: thuja (Thuja occidentalis) is the conifer most often used to set up a hedge. It does require water, so in hot summer climates it may not be your best candidate; where it has enough, it grows fast into a thick, opaque screen.
| Name | Thuja |
|---|---|
| Often misspelled as | Thuya |
| Family | Cupressaceae |
| Type | conifer, evergreen hedge |
| Height | up to 65 feet (20 meters) |
| Exposure | full sun to shade |
| Soil | ordinary, well drained |
| Foliage | evergreen |
Thuja isn’t a hedge shrub that is particularly supportive of biodiversity. Nonetheless, it’s a very fast grower and forms a thick, opaque screen. This makes it one of the most commonly used species to set up hedges.
Not every thuja is a 20-metre screen: the genus runs from towering plicata selections for tall boundaries down to knee-high globes for edging and pots. Use the table below to match height, colour and growth rate to the job you have in mind.
| Variety | Mature height | Foliage colour | Growth rate | Best use |
|---|---|---|---|---|
| ‘Zebrina’ | 30 ft (10 m) plus | Green banded creamy gold | Fast | Specimen tree or bright tall screen |
| ‘Golden Globe’ | 3-4 ft (1-1.2 m) | Golden yellow | Slow | Low edging and large containers |
| ‘Atrovirens’ | 30 ft (10 m) plus | Glossy dark green | Very fast | Tall windbreak and large hedges |
| ‘Danica’ | 1-2 ft (30-60 cm) | Deep green | Very slow | Rockery, path edging, pots |
Thuja is a conifer usually planted as part of a hedge, and is often set up at the beginning of fall, but it can also be planted until early spring or mid-spring as long as it doesn’t freeze.
When purchased in containers, a thuja can be planted in the ground almost all year round, except when it freezes.
After planting, you can also mulch the foot of the tree in order to avoid having weeds crowd it out from below but also to protect the roots from the cold.
If your thuja is never pruned, it can grow to reach nearly 65 feet (20 meters) and its bearing will be a distinctive cone.
For hedges, select the pruning height you are comfortable with as well as the thickness.
A heavy pruning late summer is enough to keep this growth under control.
That is also the season where sap descends and so it will slow the thuja’s growth a bit.
Spring pruning is usually with rising sap and tends to accelerate the tree’s growth, so this is ideal if you aim to hide yourself from prying neighbor’s view.
Sometimes you might end up in a place where a runaway thuja is gobbling up too much space in the garden. Follow these tips to cut a large thuja back.
The moment you reach for the shears changes what the plant does next, because the sap is moving in opposite directions at each season. Use the table to match the pruning time to the result you want from your hedge.
| Pruning time | Sap movement | Effect on growth | When to choose it |
|---|---|---|---|
| End of summer, heavy pruning late summer | Sap descending | Slows growth down a little | Keeping a hedge at the height and thickness you are comfortable with |
| Beginning of spring | Rising sap | Accelerates the tree’s growth | Building an opaque screen quickly to hide from prying neighbours |
| No pruning at all | Not applicable | Unchecked, very fast growth | Only where a tall specimen tree is wanted, as it reaches nearly 65 feet (20 metres) with a cone-shaped bearing |
Whichever season you pick, you can prune severely, since thuja tends to grow very, very fast.
Thuja is very disease-resistant and resists fungus, too.
The thuja tree is native to North America, where it’s commonly called Arborvitae, which means “tree of life” in Latin. This name was given it for its evergreen foliage that stays put from midwinter to early winter.
It’s also reputed to be an excellent wind-breaker, ready to resist gales of any power – and block out inquisitive neighbors, too; this particular trait is what makes it an extremely common choice for setting a hedge up.
They are also very resilient in the face of disease and pollution.
From an aesthetic point of view, it doesn’t have any other advantage than the deep green that lasts all year round and a high opaqueness.
Also, know that if the climate is hot in summer, thuja might not be your best candidate because it requires water.
When part of a hedge, think well about how high you want it to grow so that you can determine the planting distance of your thuja accordingly! Keep a spacing of about 32 inches (80 cm) to 3 feet (1 meter) for the usual 6-foot (1.80 m) hedge.
