Keeping Green Giant Arborvitae Small

If you’ve planted Green Giant Arborvitae and now you’re watching them rocket skyward, you’re not alone. These conifers are famous for fast growth and lush privacy, but you can absolutely keep them small, tidy, and happy with the right strategy. I’ve maintained compact Green Giants for years in both narrow side yards and small suburban lots, and I’ll share the exact methods that work — with no guesswork, no regrets, and no big ladders.

Understanding What You’re Up Against

Green Giant Arborvitae (Thuja ‘Green Giant’) naturally want to become large, upright evergreens — think 30 to 50 feet tall and 12 to 18 feet wide at full maturity if left alone. They can grow 2 to 3 feet per year in good conditions. That doesn’t mean you can’t keep them small; it just means the plant will always push for more size. Your job is to set gentle boundaries and stay consistent with pruning.

“Green Giant will grow as big as you let it. The trick is not to fight the plant, but to guide it — early and often.”

The Three-Part Strategy That Keeps Them Small

• Start early with shaping while growth is soft
• Prune lightly but consistently during the right windows
• Control height by managing the leader and control width with a gentle taper

If you follow those three steps and avoid cutting into old, leafless wood, you’ll keep dense, green screens that stay compact for decades.

The Best Times To Prune

Primary Window: Late Spring After the First Flush

As new growth elongates and is still soft (usually late spring to early summer), pinch or shear to your desired outline. This sets the size for the season without shocking the plant.

Light Touch-Up: Mid to Late Summer

A second, lighter shaping refines the look and keeps tips neat. Avoid heavy cuts in hot drought conditions; water first if plants are stressed.

What To Avoid: Late Fall Pruning

Skip big cuts in fall. Tender new growth may not harden before winter, risking burn and browning.

Tools That Make It Easy

• Long-blade hedge shears for smooth, even faces
• Hand pruners for selective cuts and leader control
• Bypass loppers for thicker stems (rare if you prune regularly)
• Rubbing alcohol or a disinfectant spray to clean blades between plants

Sharp tools leave clean cuts that heal quickly, which matters for conifers like arborvitae.

Step-By-Step: How I Keep Them Small

Year 1–3: Train Early

• Let the plant establish roots the first season. Water deeply and mulch.
• In late spring of year two, begin gentle shaping: trim the sides to a soft cone with a slightly wider base than top.
• Pinch the leader when it’s soft to limit height to 6–12 inches of new growth for the year.

Year 4 and Beyond: Maintain The Outline

• Each late spring, shear back the new growth on sides by 2–6 inches, depending on vigor. Always leave green foliage on the branch; arborvitae won’t reliably push from bare wood.
• Top lightly by cutting the central leader back to a strong, healthy side shoot where you still see green. I keep my hedges at 8–10 feet this way without heavy equipment.
• Repeat a light touch-up mid-summer if needed.

Annual Schedule That Works

• Early spring: Inspect for winter damage and prune out broken tips back to green.
• Late spring: Main shaping and leader control.
• Mid/late summer: Light tidy-up.
• Late fall: Only remove damaged or diseased bits, no heavy shaping.

Leader Control: The Secret To Height Management

The “leader” is the dominant central stem that drives vertical growth. Control the leader, and you control the height. In late spring, follow the leader down to a healthy side shoot with green foliage and make a clean cut just above it. Don’t remove the leader entirely; redirect it lower. If your plant throws multiple leaders after topping, choose the straightest, strongest and remove the others.

Shearing Versus Selective Thinning

Shearing with hedge clippers gives that smooth, formal look, great for screens. Selective thinning with pruners opens pockets of light and keeps the plant dense but not bulky. I often do a quick shear, then step in to hand-prune a few interior tips to maintain airflow and prevent the “pillow” look.

Shape Matters: Taper For Health

Always keep the base a bit wider than the top. This classic “Christmas tree” taper lets sunlight reach the lower branches, preventing thin legs and bare patches. Flat or inverted sides shade the bottom and cause thinning — that’s when people think their arborvitae are “dying,” but really they’re just starved for light.

Spacing If You’ve Not Planted Yet

If you haven’t planted, choose spacing that matches your eventual goal. For a compact hedge you’ll keep at 6–10 feet tall and 3–4 feet wide, space plants 5–8 feet apart. Wider spacing gives you breathing room to prune and keeps the hedge from bulking up too fast. Tight spacing forces faster vertical growth and more frequent pruning.

Can You Keep Them 6–8 Feet Forever?

Yes, with consistent leader control and light annual shearing. But understand: this is a commitment. If you skip a couple of seasons, you’ll be removing thicker wood and risk cutting past green foliage. Put it on your calendar — 20 minutes a year saves you hours later.

Fertilizing And Watering For Manageable Growth

• Go easy on nitrogen. High-N lawn fertilizer blowing into your hedge will supercharge growth. Use a balanced, slow-release product sparingly, or none at all if the plants look lush.
• Mulch 2–3 inches deep to keep roots cool and reduce watering. Keep mulch a couple of inches off the trunks.
• Water deeply during dry spells, especially in the first two years. Consistent moisture keeps foliage dense, but overwatering can push extra growth.

“My happiest, densest compact Green Giants are the ones I fertilize the least and water the smartest.”

Container And Root-Restriction Options

Want small with even less pruning? Grow Green Giant in large, sturdy containers (think 20–30 gallons or more). Containers naturally limit size through root restriction. Use a high-quality, well-draining mix, water consistently, and root-prune or up-pot every few years. In cold climates, protect containers from freeze-thaw cycles by grouping or wrapping.

Alternative Plants If You Want Low Maintenance

If the idea of annual leader control makes you sigh, consider naturally smaller cousins: Thuja occidentalis ‘Degroot’s Spire’, ‘North Pole’, or ‘Smaragd’ (Emerald Green). They’re slower, narrower, and easier to keep petite long-term.

Common Mistakes That Make Them Get Big

• Waiting too long to start pruning — you’ll end up cutting into bare wood.
• Removing all green on a branch — arborvitae may not resprout from old wood.
• Leaving the base narrow — lower branches thin and brown from shade.
• Over-fertilizing — especially with lawn runoff.
• Skipping sanitation — dirty blades can spread fungal issues.

Dealing With Browning, Winter Burn, And Pests

• Interior bronzing in fall is normal; light shedding happens inside the plant.
• Winter burn shows as brown tips on windward sides. Use burlap screens the first couple winters, water well before ground freeze, and avoid late-fall pruning.
• Check for bagworms (little hanging “bags”) and spider mites. After each shearing, give a quick inspection. A hard spray of water helps deter mites; remove bagworms by hand.

How Small Can The Width Stay?

With steady shaping, you can keep Green Giants 3–4 feet wide or even a touch less. The key is never letting the sides push beyond your outline, and always leaving some green on the branch when you cut. I set a mental “wall” and prune tips back to that same line each year.

My 5-Minute Annual Checklist

• Pick a sunny, dry day in late spring
• Clean blades and put on gloves
• Set your height and width lines in your head
• Pinch or cut the leader to hold the top
• Shear sides with a slight taper, leaving green
• Hand-prune a few interior tips for airflow
• Water deeply if the weather’s dry

Frequently Asked Questions

Can I cut into old wood to reduce size dramatically?

Not safely. Arborvitae don’t reliably push new growth from bare wood. Always leave some green on the branch when making reductions.

What if mine are already too tall?

You can lower gradually over a couple seasons. Each late spring, cut the leader back to a lower green side shoot and remove competing leaders. Avoid drastic one-time topping that exposes bare sections.

Will deer browsing help keep them small?

No. Deer create uneven, ragged hedges and can strip whole sides. Use fencing or repellents if deer are frequent visitors.

How often should I prune each year?

Once for main shaping after spring flush, plus one light tidy-up in mid to late summer if needed. That’s usually enough.

Final Thoughts From My Garden

Keeping Green Giant Arborvitae small isn’t about wrestling your plants into submission — it’s about gentle, timely guidance. Start early, trim lightly but consistently, and respect the plant’s need for green on every branch. Do that, and you can enjoy lush, compact screens that fit small spaces beautifully. I’ve turned “skyrocket” Green Giants into neat, evergreen walls that stay under 10 feet with a half hour of care each year, and you can too. Set your boundaries, keep your blades sharp, and enjoy the results all season long.