Thuja Hedge Care: Planting, Spacing and Pruning

Which Thuja Variety Should You Plant?

Almost every thuja hedge sold in North America and the UK comes down to a handful of cultivars of Thuja occidentalis (American arborvitae), plus one fast-growing hybrid that dominates the privacy-screen market.

If you garden in USDA zone 3 or a cold, exposed zone 4 site, Techny is the safest bet — it's rated hardy to zone 2 and handles wind and cold better than the others. Emerald Green is the standard choice for a tidy, narrow formal hedge almost everywhere in zones 3 through 6, and it's the variety most garden centers simply label "arborvitae."

Green Giant is tempting because it grows two to three times faster than Emerald Green, but it's only reliably hardy to zone 5, and even there it wants a sheltered site in the coldest parts of that range. It also gets enormous — 12 meters (40 feet) or more at maturity — so it's the wrong choice for a small suburban lot unless you commit to serious annual pruning to keep it in bounds.

Good to know. Nurseries sell thuja both container-grown and balled-and-burlapped. Container plants can go in the ground through most of the growing season as long as the soil isn't frozen. Balled-and-burlapped stock establishes best when planted in spring or early fall, before it has a chance to dry out in storage.

Thuja vs. Leyland Cypress for a Fast Hedge

Thuja is often compared with Leyland cypress, which grows even faster but has a much shakier track record. Leyland cypress thins out and goes bare at the base within a decade in many gardens, struggles in cold winters, and gets difficult to control if it goes even one season without a trim. Thuja is slower but far more predictable over the long run, which is why it's still the default recommendation for a hedge meant to look good for decades rather than just a few years.

How to Plant a Thuja Hedge Step by Step

Planting itself isn't complicated, but the order of operations matters. A root ball that's allowed to dry out while it waits to go in the ground, or a plant set too deep, carries that mistake for years.

You'll need a spade, a bucket or trough large enough to soak the root balls, string and stakes to keep the row straight, and a wheelbarrow if you're mixing soil in any quantity. A basic soil pH test kit is optional — thuja tolerates a fairly wide pH range, from about 6.0 to 8.0, so drainage matters far more than exact pH.

1. Soak the root balls. Set each plant in a bucket or trough of water for 15–30 minutes before planting, until it stops bubbling. A dry root ball at planting time is the single most common reason a new thuja hedge never really takes off.
2. Dig the planting holes or trench. Go as deep as the root ball and at least twice as wide. On heavy clay or very sandy ground, digging one continuous trench along the whole hedge line works better than isolated holes.
3. Loosen and amend the soil. Mix the excavated soil with compost or well-rotted manure, especially in poor or compacted ground. Thuja isn't fussy about pH, but it wants soil that holds moisture without staying waterlogged.
4. Set the plant at the right depth. The top of the root ball should sit level with, or very slightly above, the surrounding soil grade — never buried deeper. Planting too deep encourages root rot rather than stability.
5. Backfill in stages. Hold the plant upright while backfilling gradually, firming gently as you go to remove large air pockets without compacting the soil hard.
6. Water in thoroughly. Give each plant a deep soak immediately after planting, even if the soil already looks moist. This settles the soil around the roots and closes any remaining air gaps.
7. Mulch. Apply a 5–8 cm (2–3 in) layer of shredded bark or wood chips around each plant, pulled back from direct contact with the stem, to hold moisture and suppress weeds through the first year.
8. Hold off on fertilizer. Don't feed at planting time — wait at least four weeks. Fresh roots are sensitive to the salt concentration in most fertilizers.

Best Time of Year to Plant

Early-to-mid spring, once the ground has thawed and is workable, gives roots the most time to establish before the stress of summer heat and the following winter. Early fall — six to eight weeks before your average first hard frost — is the other reliable window, especially for container-grown plants. Avoid planting in the peak of summer heat if you can help it; it's possible, but it demands much more frequent watering to keep new plants from stressing out.

How Far Apart Should You Plant Thuja?

Spacing determines both how dense the hedge becomes and how long you'll wait for it to look finished. There's no single right number — it depends entirely on which variety you've chosen.

Emerald Green and Techny are typically spaced 90–150 cm (3–5 ft) apart, measured trunk to trunk, for a hedge that reads as solid within several years. Green Giant, thanks to its much faster growth and larger mature width, can be spaced further apart for the same effect: roughly 90 cm (3 ft) apart for a 1.8–2.4 m (6–8 ft) screen, out to 2.1–3 m (7–10 ft) apart if you're aiming for a screen over 4.5 m (15 ft) tall, and it should sit at least 3 m (10 ft) from fences, foundations, or septic lines given its eventual size.

Planting too tight forces plants to compete for water and nutrients, which slows overall growth more than it speeds up density. Planting too wide simply means a longer wait before the hedge closes up, but the plants themselves tend to stay healthier in the long run.

Also factor in mature width, not just height. An Emerald Green hedge can reach 90–120 cm (3–4 ft) wide at the base, and Green Giant far more than that. A hedge planted too close to a lawn, fence, or foundation eventually pushes into whatever's next to it and competes hard for moisture with anything planted nearby.

Check local setback rules before planting close to a property line — requirements vary widely by municipality and are worth confirming before you commit to a permanent hedge. If you're still weighing thuja against other options, it's worth comparing it to other hedge plants that might suit your site and timeline better.

Watering and Establishment in Year One

The first two growing seasons decide whether a thuja hedge turns into something dense and healthy or stays thin and stressed, and watering is the single biggest factor in that outcome. Thuja has a comparatively shallow root system, so it dries out faster than most people expect, even in a climate that gets regular rain.

For the first three months after planting, aim for the equivalent of about 2.5 cm (1 in) of water twice a week if rainfall doesn't cover it — a deep soak that reaches 20–30 cm (8–12 in) down is worth far more than a light daily sprinkle. Once plants are established, roughly 1.5 cm (0.5–0.6 in) of water per week, from rain or irrigation combined, is enough during a normal season.

A simple way to check is to push a finger into the soil 5–8 cm (2–3 in) deep next to the root ball. If it's dry at that depth, water. If it still feels moist, wait a couple more days.

Common mistake. Overwatering is just as damaging as underwatering. Thuja sitting in waterlogged, oxygen-poor soil develops root rot, and by the time you notice branches darkening from the base outward, the damage is often already done. Check drainage before planting in heavy clay or a low spot that collects runoff.

For a longer hedge run, a simple drip line along the base is worth the setup cost. It delivers steady moisture right at the roots with far less evaporation loss than overhead watering, and it saves you from dragging a hose down the row every evening in July.

Feeding a Thuja Hedge: When and With What

Thuja isn't a heavy feeder compared to, say, a lawn, but a consistent feeding schedule noticeably improves both color and density. Never fertilize at planting time — wait at least four weeks so new roots have time to adjust.

A slow-release, granular evergreen fertilizer scattered around the root zone in spring is enough for most home gardens. Water it in well afterward, or it sits on the surface instead of reaching the roots. If your hedge already looks healthy and evenly dark green, once a year is plenty — pushing extra nitrogen doesn't make a hedge denser, it just produces soft growth that's more vulnerable to winter injury.

An even, pale or yellowish cast across the whole hedge, rather than browning on one side, more often points to a nutrient shortfall than to disease or drought — common on sandy soil or where a heavily fed, frequently mowed lawn is out-competing the hedge roots for nitrogen. Compost or well-rotted manure works well as a supplement since it releases nutrients slowly and is far less likely to burn roots than a strong mineral feed. For a deeper look at how nitrogen, phosphorus and potassium actually affect plant growth, see the guide to NPK fertilizer.

Pruning and Shaping a Thuja Hedge

Thuja needs noticeably less pruning than deciduous hedging like privet or beech. Emerald Green and Techny largely hold their shape on their own and often get by with a single trim a year. Green Giant, given its much faster growth, benefits from two — one in early summer and a second in late summer.

Prune between late spring and mid-summer. Stop by late summer at the latest so new growth has time to harden before the first hard frost. Trimming too late in the season leaves soft, tender growth exposed right when cold weather arrives, and that growth is usually the first to brown.

The one rule that matters most. Only cut into green, living growth. Unlike many deciduous hedges, thuja can't resprout from old, bare, brown wood. Cut too deep and you've created a permanent gap that will never fill back in, no matter how long you wait.

Shape the hedge slightly narrower at the top than at the base — close to a flat-sided A. That lets light reach the lower branches and keeps the hedge full all the way down instead of going bare at the bottom after a few years. A string line stretched between two stakes at your target height makes it much easier to cut a straight, even top over a long run.

For a short hedge, hand shears do the job fine; a corded or battery hedge trimmer saves real time on a longer run. Check the blades before you start — dull blades tear rather than cut, leaving ragged brown edges that stay visible for weeks. Work in smooth, sweeping passes rather than hacking at the hedge section by section, and check back against your guide line regularly so you don't cut a wavy edge without noticing. The same core principles apply to hedges generally, covered in more detail in the guide on when to trim a hedge.

Winter Protection for Thuja

A properly hardy variety for your zone usually gets through winter without special protection once established. What actually causes winter damage is rarely the cold itself — it's usually a combination of strong winter sun, drying wind, and cold snaps that arrive before the plant has fully hardened off.

Young plants, in their first year or two in the ground, are the most vulnerable. Winter sun combined with frozen ground means the foliage keeps losing moisture that the roots can't replace, producing the characteristic browning on the sun- and wind-facing side. A simple burlap screen on the most exposed side — usually south or southwest — cuts that risk substantially for the first couple of winters.

A deep watering in late fall, before the ground freezes, matters just as much as physical protection. A plant that goes into winter with well-hydrated roots handles drying winds far better than one that's already borderline.

Heavy, wet snow can also splay or snap branches on a dense thuja hedge, especially upright, narrow varieties like Emerald Green. Brush heavy snow load off gently with an upward sweep of a broom rather than shaking or striking the branches, which are more brittle when frozen. A branch that's already been pushed out of shape by snow load rarely springs back fully on its own — loosely tie it back toward the trunk with soft twine until it retrains itself.

Good to know. Thuja tolerates road salt very poorly. If the hedge sits near a driveway, sidewalk, or street that gets salted in winter, avoid piling salted snow against the base and rinse foliage that's been splashed with salt spray as soon as the weather allows.

For broader guidance on protecting cold-sensitive plants through winter, including which species are most at risk, see the full guide to winter plant protection.

Why Is My Thuja Turning Brown or Yellow?

Browning on thuja usually traces back to one of four causes, and it's worth identifying which one before doing anything about it — the fix looks completely different depending on the cause.

There's an uncomfortable truth with no way around it: brown, dead foliage never turns green again. Once the chlorophyll is gone, that tissue is dead, whatever you do afterward. The only real fix is to prune out the dead sections — assuming enough healthy green wood remains underneath — and then make sure the underlying cause, whether that's drought, poor drainage, or winter stress, doesn't repeat itself.

Beyond fungal issues, a handful of pests specifically target thuja. Spider mites show up as fine, dusty webbing between branches and stippled, yellowing scale-leaves, and they thrive in hot, dry summers — often a sign the hedge is already water-stressed. Bagworms build small, hanging cocoon-like cases out of foliage fragments that are easy to mistake for tiny cones, and a heavy, untreated infestation can strip entire branches bare. Scale insects appear as small, waxy brown bumps along the stems and often leave a sticky residue behind. A light infestation of any of these rarely does serious harm to an otherwise healthy, well-established hedge, but it's worth walking the hedge line once a month through summer and removing or hosing off visibly affected shoot tips before a problem spreads. For a broader rundown of what else might be causing damage, see the guide to identifying garden pests.

Common Thuja Hedge Mistakes

• Planting too deep. The root ball should sit level with the surrounding grade. Deeper planting suffocates roots and invites root rot.
• Skipping the pre-planting soak. A dry root ball set straight into the ground rarely catches up, no matter how much you water afterward.
• Fertilizing on planting day. Fresh roots are easily burned by the salt concentration in most fertilizers. Wait at least four weeks.
• Cutting into brown, dead wood. Unlike many deciduous hedges, thuja never recovers from a cut into old, bare wood.
• Planting too close together out of impatience. Competition for water and nutrients slows growth more than tight spacing speeds up fill-in.
• Ignoring drainage. A low spot that collects water is the most common reason an otherwise correctly planted thuja dies within a couple of years.
• Pruning too late in the season. Soft new growth that hasn't hardened off before the first hard frost is the growth most likely to brown.
• Choosing the wrong variety for the climate. A fast-growing Green Giant in an exposed zone 4 site often ends up thin and winter-damaged. A hardier variety like Emerald Green or Techny is the safer bet in cold, windy locations.

Frequently Asked Questions

How far from a property line should you plant a thuja hedge?
There's no universal rule — setback requirements vary by municipality and sometimes by HOA. A common practical minimum is about 60 cm (2 ft) for a hedge kept under 1.8–2 m (6 ft), and more if it will grow taller. Check local rules and talk to your neighbor before planting close to a boundary.

How fast does thuja grow per year?
It depends heavily on the variety. Emerald Green and Techny typically grow 30–60 cm (1–2 ft) a year, while Green Giant can put on 90–150 cm (3–5 ft) in a good year. Dwarf varieties like Danica grow far slower, usually under 15 cm (6 in) annually.

Is spring or fall better for planting thuja?
Both work, but early-to-mid spring gives the most reliable results in most climates since plants have a full season to root in before summer heat and the following winter. Early fall also works well for container-grown plants, ideally six to eight weeks before your first hard frost.

Does thuja need winter protection?
An established, appropriately hardy variety usually doesn't need protection. Young plants in exposed, sunny, or windy sites benefit from a simple burlap screen on the most exposed side for their first couple of winters.

Can brown thuja turn green again?
No. Foliage that has already browned and died will not recover. Prune out the dead sections if enough healthy green growth remains underneath, and address the underlying cause — usually drought, poor drainage, or winter sun — so it doesn't happen again.

How often should a newly planted thuja hedge be watered?
Plan on the equivalent of about 2.5 cm (1 in) of water twice a week for the first three months if rain doesn't cover it. After that, roughly 1.5 cm (0.5–0.6 in) a week is usually enough during a normal growing season.

Can thuja handle shade?
Thuja grows best in full sun to light shade. In deep shade it thins out noticeably, especially on the shaded side, because the foliage needs light to stay dense. Aim for at least six hours of direct sun for the fullest hedge.

What's the best fertilizer for thuja?
A slow-release, granular evergreen fertilizer or a balanced NPK blend around 10-8-6, applied once in spring, is enough for most home gardens. Skip nitrogen feeding after late summer, since it encourages soft growth that winter can damage.

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