How to prune a thuja hedge: complete guide

Why thuja pruning is different

Thuja (arborvitae) is much more forgiving than Leyland cypress when it comes to pruning. While Leyland cypress never recovers from dead wood, thuja bounces back - even from years-old brown branches. This makes thuja ideal for hedges that need hard cutting back, reshaping, and adjustment.

The most common varieties are "Smaragd" (green, columnar) and "Brabant" (slightly wider, dark green). Both tolerate aggressive pruning far better than conifers like cypress.

Timing: the full pruning schedule

Thuja offers more flexibility than Leyland cypress, but a fixed schedule helps:

Spring (March-April): First pruning of the year

• Thuja starts growing after winter
• Remove any dead branches or damaged sections
• Cut sides and shape height carefully
• This is BEST moment for hard cutting

Summer (June-July): Second trim

• Light trim to maintain shape
• Remove all drooping branches
• Not necessary, but helps keep tight form

Autumn (September): Pre-winter prep

• Light trim only
• No hard pruning - thuja must build strength for winter

Winter (October-March): No pruning

• Tree is dormant, wounds heal slowly
• Exceptions: remove snow-damaged branches immediately

Techniques: sides, top, overall form

Sides

Thuja grows dense and can look wild quickly. Sides are most visible:

• Prune March-April, angled cut bottom-to-top (45 degrees)
• This helps water run off and gives side foliage more sunlight
• Remove everything beyond your desired profile
• Sides can be cut HARD (back 10-15 cm from previous year) - thuja recovers well

Top

• Flat profile: cut horizontally across the top
• Pointed profile: cut two diagonal cuts downward
• Thuja grows tall fast, so annual trimming is needed
• Can be cut back 20-30 cm per year and recovers

Full shape

• Wide base, narrow top (trapezoid): gives every level more light
• Rectangular shape (modern look): also fine, but requires more maintenance

Step-by-step basic pruning

1. Inspection and planning (March)

Look at your hedge. Any asymmetry? Drooping branches? Make notes of what needs to go.

2. Sides first

Start low, angled cut upward. Work left to right. Ensure both sides taper wider toward bottom.

3. Top

Flat or pointed? Choose and cut consistently. Preference: pointed (energy goes up, not wasted sideways).

4. Spreading

Remove all branches spreading out at the bottom. This gives room below for light and moisture.

5. Details

Step back, review. Gaps? Light trim the other side for balance. Drooping branches? Off they go.

Shape applications

Rectangle (most common):

• Sides vertical, top flat
• Easy maintenance, modern look
• Suits formal gardens

Trapezoid (wide bottom, narrow top):

• More light reaches the bottom of hedge
• Lower branches get more sunshine
• Dense and full to the base

Triangle / Pointed (top point):

• Water drains well
• Snow rolls off rather than piling
• Classic landscape style

Rounded top (semi-formal):

• Softer appearance
• More maintenance (more cut lines)
• Popular in cottage gardens

Frequently asked questions

My thuja hedge has turned completely brown inside. Can it recover?

Yes. This often happens when hedges skip pruning for years - they thicken, the inside gets no light, and foliage dies. Good news: thuja regrows from brown wood. Plan for next spring:

1. Cut sides back 10-15 cm from the old perimeter (aggressive)
2. Open the top more by cutting lower (less dense)
3. Next spring thuja will sprout new shoots from all that brown wood

Full recovery takes 2-3 seasons, but it works.

Can I prune hard in autumn?

Better not. Thuja builds strength for winter. Hard cutting in September-October shocks the tree, wounds heal poorly, frost can damage. Wait until March.

How fast does thuja regrow?

Fast. After March pruning you see new growth in 3-4 weeks. By June, 15-20 cm of new growth is normal. This is why summer maintenance is useful - otherwise your hedge spreads wild.

Do I have to cut my hedge back hard if it has grown too tall?

No. Thuja accepts gradual reshaping. Cut 30-50 cm off the top each year. After 2-3 years you reach desired height without shocking the tree.

How old can a thuja hedge get?

Decades. Many Dutch hedges stand 30-50 years without major issues. With annual pruning, thuja stays compact and full. Without care it becomes a forest.

Step-by-step

Step 1: Prepare tools

Sharp hedge trimmer or hand shears, work boots, gloves. Check for snow damage (remove immediately).

Step 2: Sides

Start bottom-left, 45-degree cut upward. Inspect both sides. Remove drooping branches.

Step 3: Top

Flat or pointed? Usually: flat top. Cut horizontally along desired height.

Step 4: Front

Same technique as sides. Light trim. Check symmetry.

Step 5: Back

Lighter trim usually OK. No one sees it, but helps air circulation.

Cultivar differences

Smaragd (green, columnar):

• Narrow and upright, ideal for tight spaces
• Grows much vertical, less horizontal
• Trim top more than sides

Brabant (wider, dark green):

• Wider and fuller appearance
• Grows faster horizontally
• More side trimming needed

Degroot's Spire (very slender):

• Normal pruning, follows natural form
• Less aggressive shaping needed

Case study: Rehabilitating neglected hedge

Many homes inherit neglected thuja hedges:

Year 1 (March): Hard cut. Sides back 20-30 cm, top 50 cm lower. Hedge looks brown and thin. Normal.

Summer Year 1: Light trim only. No hard cutting.

Year 2 (March): Sides back 15 cm again, top another 30-40 cm. Green starts returning.

Year 3 (March): Normal maintenance. Hedge looks normal.

With patience and consistent pruning, almost every thuja recovers.

Maintenance calendar

• March: First major trim (sides, top)
• June: Light summer trim
• September: Light autumn check
• October-February: Snow damage inspection

Discover your garden design

At [gardenworld.app](https://gardenworld.app) you can upload your front yard and see your thuja hedge in context with other plantings. Design your perfect hedge shape and see how it grows and fits in your garden.

Thuja is a faithful plant. With yearly care your hedge stays healthy, tight and full for generations.