Pocket Botanist
Check these first
- Observe how many hours of direct sunlight the tree receives daily.
- Check the inner branches for signs of green growth versus bare wood.
- Inspect the surrounding area for new structures or plants blocking the light.
Likely causes
Insufficient Sunlight
Most likelyHow to tell: The inner branches lose needles and the outer growth becomes sparse and stretched out. This happens when the tree is shaded by buildings or larger trees.
What to do: Move the plant to a spot with full sun if it is in a container. For trees in the ground, prune back overhanging branches from nearby trees to increase light exposure.
Improper Pruning
PossibleHow to tell: The tree has large gaps or bare patches where branches were cut back too far into the old wood. Thuja does not grow new needles from old, woody stems.
What to do: Avoid cutting into the brown, woody interior of the branches. Only trim the soft, green outer foliage to maintain shape and encourage density.
Find out what's wrong with your arborvitae
The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.
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When to worry
It is a concern if the tree is losing its privacy screen density. Some minor thinning in the deep interior is normal as the tree matures.
Stopping it coming back
Plant your Thuja in a location that receives at least 6 to 8 hours of direct sun every day.
Keep your arborvitae healthy from here
Save your plant in Pocket Botanist and you get care reminders timed for this plant, plus a care history that shows what worked. Identification and a health check are free.
Questions people ask
- Can I prune my leggy Thuja to make it grow back thicker?
- Unfortunately, no. Thuja will not sprout new growth from old, woody branches, so pruning will only create permanent gaps.
- Will a leggy Thuja fill in on its own?
- If the legginess is caused by lack of light, it will not fill in until the light situation is corrected. Once it gets more sun, it will grow new, healthy foliage on the outer tips.
More problems with Arborvitae
This article was generated with AI from the plant’s care profile and is general information, not horticultural advice. Read about how we build these guides.