Techny arborvitae

Sun

Full sun to partial shade; growth is densest with at least 6 hours of direct sun.

Water

Moderate; keep the root zone evenly moist, especially during establishment and dry weather. Avoid prolonged waterlogging.

Soil

Moist, well-drained loam is ideal; tolerates clay and alkaline soil if drainage is adequate. Poorly suited to hot, dry, sandy sites.

Height

10-15 ft (3-4.6 m), eventually reaching 20 ft (6 m) in favourable conditions

Spread

6-10 ft (1.8-3 m)

Foliage

Evergreen. Dense, flattened sprays of dark green, scale-like leaves; aromatic when crushed, with relatively little winter bronzing.

Growth

Slow to moderate, commonly 6-12 in (15-30 cm) per year once established.

Care needed

Low

• Cold hardy
• Wildlife

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   3 ft (1 m)

3. After 2 years

   5 ft (1.5 m)

4. After 3 years

   7 ft (2 m)

5. After 5 years

   10 ft (3 m)

About 7 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Native to

the US and Canada

Growth rate

Slow

• Water deeply during dry spells for the first two growing seasons; established plants also need water during prolonged drought.
• Spread 2-3 in (5-8 cm) of organic mulch over the root zone, keeping it clear of the trunk.
• Feed lightly in spring only if growth is weak or a soil test indicates a deficiency; avoid late-season nitrogen.
• Protect young plants from deer with fencing where browsing is common.
• In cold climates, water thoroughly before the ground freezes if autumn has been dry.

Pruning. Lightly trim in late spring or early summer to maintain a hedge, keeping its base wider than its top. Cut only within green growth: bare old wood usually does not produce new shoots.

Early spring

Remove dead or broken branches and check for winter damage before new growth begins.

Spring

Plant while conditions are cool and moist; renew mulch and water new plants deeply.

Late spring

Lightly trim hedges without cutting back into bare wood.

Summer

Check soil moisture during dry spells and inspect foliage for bagworms or mite damage.

Late autumn

Water before freezing weather if soil is dry, and install deer protection where needed.

Winter

Keep de-icing salt away from roots and foliage; do not strike or bend frozen branches to remove ice.

• Plant as a broad evergreen privacy screen, allowing room for its mature width rather than crowding it against a fence.
• Use as a clipped boundary hedge with a wide base for year-round enclosure.
• Place individual plants at the back of mixed borders to give flowering shrubs and perennials a dark green backdrop.
• Repeat along a large garden boundary for winter structure and visual rhythm.

Garden styles it suits: Formal, Traditional, Grand estate, Green on green, Winter interest and Low-maintenance.

Plant it with: Panicle hydrangea, Siberian iris, Hosta, Astilbe, Red-twig dogwood and Purple coneflower.

Wildlife: Dense foliage provides shelter and nesting cover for birds. Deer browse the foliage, and birds and small mammals may eat the seeds.

• Deer browsing: foliage can be stripped severely in winter; use a properly maintained deer fence rather than relying solely on repellents.
• Bagworms: pick off and destroy bags before eggs hatch; where locally appropriate, treat small, actively feeding larvae with a labelled Bacillus thuringiensis product.
• Spider mites: fine stippling and dull foliage can develop in hot, dry weather; check for mites, rinse foliage with water and use a labelled treatment if damage continues.
• Browning and dieback: drought, winter drying, salt exposure or waterlogged roots can cause similar symptoms; check soil moisture and drainage before changing watering, and keep road salt away.

Foliage and especially concentrated essential oil contain thujone and can be harmful if swallowed by people or animals, including cats, dogs and horses. Eating foliage may cause digestive upset; substantial ingestion or ingestion of the oil can cause serious poisoning. Do not use it for homemade teas or remedies.

• Emerald Green arborvitae (Thuja occidentalis 'Smaragd')

  Usually much narrower and more columnar, with brighter emerald-green foliage; 'Techny' develops a broader, darker green pyramid.

• Green Giant arborvitae (Thuja standishii × Thuja plicata 'Green Giant')

  Grows much faster and becomes a substantially taller tree, with a looser outline and larger foliage sprays.

• Oriental arborvitae (Platycladus orientalis)

  Its foliage sprays tend to stand in vertical planes, and its young cones are fleshy and bluish with prominent hooked scales; 'Techny' has small, slender brown cones.

'Techny' is named for Techny, Illinois, where this selection originated.

Propagation. Root semi-ripe cuttings in late summer under humid conditions with a free-draining rooting medium. Seedlings will not reliably retain the characteristics of 'Techny'.

Accepted botanical name

Thuja occidentalis

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Connecticut, Illinois, Indiana, Kentucky, Maine, Manitoba, Maryland, Masachusettes, Michigan, Minnesota, New Brunswick and New Hampshire.

Measured

Soil pH 5.2 to 7. Average height 1460 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.