Arborvitae care guide: when & how to prune, fertilize and spray
Thuja occidentalis / T. 'Green Giant' · USDA zones 3–8
Popular columnar evergreen for privacy screens. Prune lightly. Arborvitae won't regrow from bare brown wood inside the plant.
☀️ Sun
Full sun.
💧 Water
Even moisture; very prone to drought stress and winter burn.
🪱 Soil
pH 6.0–8.0. Moist, well-drained. Compost at planting.
How and when to prune arborvitae
Light trim after new growth
When: 6–10 weeks after the last spring frost.
- zones 3–5: about Jun 21 – Jul 19
- zones 6–7: about May 27 – Jun 24
- zones 8–10: about Apr 8 – May 6
Arborvitae only regrows from green foliage. A light annual trim keeps it dense without making bare spots.
- Trim only the new, light-green growth, no more than one-third of it.
- Never cut into brown interior wood. It won't regrow.
- Leave the top a bit narrower than the bottom.
Tools: Hedge shears
Fertilizing arborvitae
Spring feeding
When: from 1 week before to 3 weeks after the last spring frost.
- zones 3–5: about May 3–31
- zones 6–7: about Apr 8 – May 6
- zones 8–10: about Feb 18 – Mar 18
A single spring feeding as growth starts covers most shrubs for the year.
- Scatter fertilizer at the label rate from near the stems out past the drip line, where the feeder roots are.
- Water it in thoroughly.
What to use: 🌿 Balanced organic granular fertilizer (e.g. Espoma Plant-tone 5-3-3) · Slow-release balanced fertilizer (e.g. Osmocote Smart-Release 14-14-14)
Spraying & disease prevention for arborvitae
Bagworm check
When: 7–10 weeks after the last spring frost.
- zones 3–5: about Jun 28 – Jul 19
- zones 6–7: about Jun 3–24
- zones 8–10: about Apr 15 – May 6
Young bagworms hatch in early summer and are easy to kill. By late summer they're protected in tough bags.
- Look for tiny new bags (¼ in / 6 mm) at branch tips.
- If you find them, spray Bt or spinosad, covering all the foliage.
What to use: 🌿 Bt, Bacillus thuringiensis var. kurstaki (e.g. Thuricide, Dipel) · 🌿 Spinosad (e.g. Captain Jack's Deadbug Brew)
Frost & winter protection for arborvitae
Deep-water before the ground freezes
When: from 1 week before to 4 weeks after the first fall frost.
- zones 3–5: about Sep 24 – Oct 29
- zones 6–7: about Oct 18 – Nov 22
- zones 8–10: about Nov 24 – Dec 29
Evergreens keep losing water through their leaves all winter. Going into winter well hydrated prevents winter burn (brown, scorched foliage).
- If autumn has been dry, give a slow, deep soak: about 10 gallons (40 L) per inch of trunk diameter, or 1 in (2.5 cm) of water across the root zone.
- Repeat every 2–3 weeks until the ground freezes.
- Optionally spray an anti-desiccant (e.g. Wilt-Pruf) on a mild day above 40°F/4°C.
Common arborvitae problems and how to fix them
Bagworms
Signs: Spindle-shaped bags of needles hanging from branches.
What to do: Hand-pick bags in fall through spring. Spray Bt or spinosad in early summer while the caterpillars are small.
Snow splaying
Signs: Stems bent open by snow.
What to do: Gently brush snow off upward. Tie the tops loosely with soft twine for winter.
Spider mites
Signs: Bronzed, dusty foliage in hot, dry weather.
What to do: Hose foliage. Horticultural oil.
Arborvitae care FAQ
When should I prune arborvitae?
Light trim after new growth: 6–10 weeks after the last spring frost (around May 27 – Jun 24 in zones 6–7). Popular columnar evergreen for privacy screens. Prune lightly. Arborvitae won't regrow from bare brown wood inside the plant.
What is the best fertilizer for arborvitae?
A single spring feeding as growth starts covers most shrubs for the year. Good options: Balanced organic granular fertilizer (e.g. Espoma Plant-tone 5-3-3); Slow-release balanced fertilizer (e.g. Osmocote Smart-Release 14-14-14).
What should I spray on arborvitae?
Bagworm check (7–10 weeks after the last spring frost). Products: Bt, Bacillus thuringiensis var. kurstaki (e.g. Thuricide, Dipel); Spinosad (e.g. Captain Jack's Deadbug Brew). Always follow the label.
What soil does arborvitae need?
Moist, well-drained. Preferred pH 6.0–8.0. Compost at planting.
How much sun and water does arborvitae need?
Sun: Full sun. Water: Even moisture; very prone to drought stress and winter burn.
What are common arborvitae problems?
Bagworms: Spindle-shaped bags of needles hanging from branches. Hand-pick bags in fall through spring. Spray Bt or spinosad in early summer while the caterpillars are small. Snow splaying: Stems bent open by snow. Gently brush snow off upward. Tie the tops loosely with soft twine for winter. Spider mites: Bronzed, dusty foliage in hot, dry weather. Hose foliage. Horticultural oil.
More evergreens care guides
Timings are given relative to your average frost dates, with examples for typical US climates. Always read and follow product labels.