When to prune thuja?
- Botanical name
- Thuja occidentalis
- Family
- Cupressaceae
Thuja is pruned from March to July. It is planted from September to February.
Thuja is a woody perennial.
Thuja takes shearing and makes a close hedge. Left unsheared it grows into a large tree, and sheared regularly it holds whatever height is chosen for it. The hedge is shaped wider at the base than at the top. Light then reaches the lower branches as well.
After midsummer the shearing stops. Shoots that grow then do not ripen before winter.
Gloves go on for the shearing, because the oil in the shoots irritates the skin. The poison sits in the shoot tips and in the cones, which is exactly what comes off. Swallowed, it causes vomiting, diarrhoea and stomach pain.
Thuja through the year
- pruning
- planting
In short
Growing conditions
Is thuja toxic to people?
Yes. Toxic to people, toxic parts: roots, stems, bark, leaves and seeds.
Pests and diseases
Listed here is every problem for which the sources name this plant as a host. The problems are not listed in order of how common they are.
- Signs
- The plant dies suddenly, often in mid season and without any decline beforehand. Peel the bark at ground level and under it there is a white or cream sheet of fungal tissue, thin as the skin of a mushroom. In the soil there are black or brown strands like bootlaces. In late summer and autumn tufts of honey brown mushrooms with a whitish ring on the stalk appear by the stumps or over dead roots.
- Prevention
- The fungus spreads through the soil with its strands, from a few centimetres to a good hand's width below the surface, and infects the roots of a living plant when it touches them. So do not leave stumps and dead roots in the ground. No plant is completely resistant, but privet, lilac, viburnum, weigela, forsythia, butterfly bush, rhododendron, thuja and walnut are particularly susceptible.
- What to do
- There are no products. The only thing that works is digging out and removing every infected root and stump, which takes away the food without which the strands in the soil do not grow. A vertical barrier of rubber or thick plastic sheet, buried about half a metre deep and standing a few centimetres above ground, stops the spread into an unaffected part of the garden.
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Related plants
The plant below is in the same botanical family (Cupressaceae).
Sources about the plant: DGUV Information 202-023 „Giftpflanzen, GBIF Backbone Taxonomy, Informationszentrale gegen Vergiftungen, Universitätsklinikum Bonn, Iowa State University Extension, NC State Extension Plant Toolbox, Oregon State University, Penn State Extension, Royal Horticultural Society, Wikidata. Checked between 14 and 28 August 2026.