Thuja hedge care – watering, feeding, pruning and winter protection

Water the roots, not just the surface

After planting, water the root balls and surrounding soil thoroughly. During establishment, check both: moist soil nearby does not tell you on its own whether water has reached the root ball.

For later watering, inspect moisture below the surface in the rooting area. Check more closely during hot, dry or windy conditions. Plant size, rainfall and drainage affect how quickly the soil dries.

When watering is needed, apply enough for water to reach the root zone rather than repeatedly wetting only the surface. Check afterwards that it has reached the area you intended to water.

If the soil remains wet or water stands around the plants, investigate drainage before adding more. A dry surface and a wet root zone can require different decisions.

An established hedge still needs attention during prolonged dry weather or after changes to drainage and surrounding planting. There is no single litre amount or watering interval that suits every hedge.

Keep the root area clear

Grass and weeds compete with a young hedge for water. Keep them under control around the plants.

Mulch can reduce evaporation, but leave the stems and plant bases clear. Choose the depth for the mulch product rather than using it to compensate for poor drainage or an unsuitable planting bed.

Feed only when there is a reason

Do not treat browning alone as proof that the hedge needs fertiliser. First check moisture, drainage and the pattern of the damage.

If feeding is needed, use the product’s local label for dose and timing. Product composition matters: a high-nitrogen feed and a low-nitrogen autumn product are not interchangeable.

A month recommended for a named plant or product in Finland is not a shared GB/Australian schedule. Northern and southern seasons differ, and tropical parts of Australia may be better described by wet and dry seasons. Use guidance for the plant, product and climate where the hedge grows.

Trim green growth; be cautious with bare wood

For routine shaping, keep cuts within the green growth. Do not assume that an old bare section will fill out after a hard cut.

RHS guidance notes that most conifers regenerate poorly from old wood. Thuja can be an exception, but regrowth is less reliable; species, cultivar and the condition of the hedge matter.

For GB readers, RHS guidance places routine trimming of green growth from spring to late summer. That is not a calendar to copy unchanged into Australia. Follow local nursery advice for the cultivar and avoid trimming during hot, dry conditions. Get advice before substantial reduction into bare wood.

Check for active bird nests before cutting.

Winter protection depends on exposure and climate

In cold locations, evergreen foliage can lose moisture in sun and wind while frozen soil limits water uptake. Young or exposed plants may therefore need protection suited to the site.

If the rooting soil is dry before an expected freeze, water while it can still absorb water. Protective screening should allow air movement and must not rub against the foliage.

This is advice for the conditions described, not a requirement for every GB or Australian garden. Where soil does not freeze, assess local heat, wind and moisture problems instead of following a northern spring-shading calendar.

Brown patches: decide what to check next

The position and spread of browning can help you choose the next check, but they do not establish a diagnosis.

Do not assume every brown patch has the same cause. If damage spreads quickly, branches die or the checks do not explain the symptoms, ask a nursery or garden professional for an assessment.