Holmstrup arborvitae

Sun

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

Water

Keep the root zone evenly moist, especially during establishment and dry summers. Established plants tolerate brief dry spells but not prolonged drought.

Soil

Moist, well-drained loam or clay loam; tolerates acidic to alkaline soil. Avoid persistently waterlogged or very dry, shallow soil.

Height

8-12 ft (2.4-3.7 m), eventually reaching about 15 ft (4.6 m) in favourable conditions

Spread

3-5 ft (0.9-1.5 m)

Foliage

Evergreen. Dense, scale-like green leaves in upright, flattened sprays; generally holds its green colour well through winter, though some bronzing can occur in exposed conditions.

Growth

Slow, commonly about 4-8 in (10-20 cm) a 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

   2.7 ft (0.82 m)

3. After 2 years

   4 ft (1.1 m)

4. After 3 years

   5 ft (1.5 m)

5. After 5 years

   7 ft (2.1 m)

About 8 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

• Plant with the root flare at soil level and water the entire root ball thoroughly.
• Check soil moisture regularly during the first two growing seasons; water deeply when the upper soil begins to dry.
• Spread 2-3 in (5-8 cm) of organic mulch over the root zone, keeping it clear of the stems.
• Feed lightly in spring only if growth is weak or a soil test indicates a deficiency; avoid late-season nitrogen.
• Water during dry autumn weather before the ground freezes, and avoid sites exposed to road salt.

Pruning. Usually needs little pruning beyond removing dead or damaged shoots. If shaping a hedge, trim lightly in late spring or early summer, keeping the base wider than the top and never cutting back into bare, brown wood.

Early spring

Check for winter damage and remove dead or broken branches once severe cold has passed.

Spring

Plant new shrubs, water thoroughly and refresh mulch without piling it against the stems.

Late spring

Lightly trim new growth if a more formal outline is needed.

Summer

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

Autumn

Water deeply during dry weather, particularly before freezing conditions.

Winter

Gently brush off loose, heavy snow before it bends branches; do not knock off ice or frozen snow.

• Plant in a row for a compact evergreen hedge or screen, allowing room for the mature width.
• Use a matching pair beside an entrance or path for a restrained, formal accent.
• Repeat individual plants through a mixed border to provide vertical structure among rounded shrubs and perennials.
• Place behind flowering perennials as a quiet green backdrop that remains after the flowers fade.

Garden styles it suits: Formal, Traditional, Architectural minimal, Small-space, Winter interest and Green on green.

Plant it with: Panicle hydrangea, Hosta, Coral bells, Siberian iris, Purple coneflower and Japanese forest grass.

Wildlife: Dense foliage offers shelter and nesting cover for small birds. Deer may browse it heavily, especially in winter; it is not a dependable deer-resistant screen.

• Winter browning: frozen or dry soil and drying winds can scorch foliage. Water during dry autumn weather, mulch the roots and provide a windbreak in exposed positions.
• Bagworms, particularly in parts of North America: remove and destroy hanging bags before eggs hatch; treat young feeding larvae with a locally approved control if necessary.
• Spider mites: fine stippling and dull, bronzed foliage can develop during hot, dry weather. Confirm mites by tapping a branch over white paper, then rinse foliage thoroughly and use an approved treatment if damage continues.
• Root rot in poorly drained soil: yellowing, wilting and dieback may follow prolonged saturation. Correct drainage and watering; replace severely affected plants rather than replanting into the same wet conditions.

Treat the foliage, young twigs and their oils as toxic if eaten by people, cats, dogs or horses. They contain thujone and related compounds that can cause digestive upset; substantial ingestion or concentrated oil can cause serious poisoning. Sap may irritate sensitive skin. Keep clippings away from livestock and do not use the foliage for homemade teas or remedies.

• Emerald Green arborvitae (Thuja occidentalis 'Smaragd')

  Usually taller and faster-growing, with a more sharply tapered outline and finer-looking, glossy green sprays. Small nursery plants can be difficult to distinguish reliably without labels.

• Degroot's Spire arborvitae (Thuja occidentalis 'Degroot's Spire')

  Develops a narrower, spire-like outline with conspicuously twisted or sculpted foliage sprays; 'Holmstrup' has a fuller, more evenly dense outline.

• Oriental arborvitae (Platycladus orientalis)

  Its foliage sprays tend to stand in vertical planes, and its cones have prominent horn-like tips. Thuja occidentalis has small, elongated cones without those horns.

Arborvitae means 'tree of life' in Latin, while occidentalis means 'western', distinguishing this North American species from its Asian relatives.

Propagation. Take semi-ripe cuttings in late summer or early autumn and root them in a free-draining medium under humid conditions. Seedlings will not reliably retain the compact form of 'Holmstrup'.

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.