Arborvitae — Thuja occidentalis (American Arborvitae)

Overview: Cold-hardy, evergreen conifer native to the Great Lakes and Northeast. Dense, fine-textured, aromatic foliage in flat sprays; small tan cones. Naturally pyramidal to columnar; widely used for hedges/screens and foundation accents.

Size & habit (species): 40–60′ tall × 10–15′ wide in time. Cultivars range from true dwarfs (2–4′) to narrow columns (12–20’+).

Growth rate: Moderate. Typical hedging types add ~6–12″ per year (some vigorous forms 12–18″).

Hardiness: USDA Zones 2–7 (excellent for Michigan).

Light: Full sun to partial shade (densest growth in full sun).

Soil & water: Prefers moist, well-drained, slightly alkaline to neutral soils; tolerates limestone. Shallow, fibrous roots—mulch helps retain moisture. Avoid prolonged drought and waterlogged sites.

Tolerance/concerns:

• Deer: Highly browsed—protect young plants (fencing/repellents).

• Winter burn: Can bronze or scorch in windy, exposed, or salty locations; consider burlap screens the first winters.

• Salt: Poor tolerance to road salt.

• Pests: Arborvitae leafminer, spider mites, and bagworm; monitor in midsummer.

• Disease: Root rots (e.g., Phytophthora) in poorly drained soils.

Pruning: Light shear after spring flush; avoid cutting into old brown wood (limited back-budding). Maintain single leader on taller forms to prevent snow split.

Landscape uses: Privacy hedges, property lines, windbreaks, narrow screens, formal sheared shapes, and small-space accents (dwarfs in beds/containers).

Spacing (hedges, on-center):

• Narrow columns like ‘Smaragd’/Emerald Green: 2–3 ft

• Broader hedging types like ‘Techny’: 4–6 ft

• Species/large forms: 8–12 ft

Notable cultivars (quick picks):

• ‘Smaragd’ (Emerald Green): 12–15′ H × 3–4′ W, tight column, holds color well.

• ‘Techny’ (‘Mission’): 10–15′ H × 6–8′ W, sturdy, dark green, good winter color.

• ‘Nigra’: 20–30′ H × 5–10′ W, rich dark green all year.

• ‘Brandon’: 15–20′ H × 3–5′ W, narrow, cold-tough.

• ‘Holmstrup’: 8–12′ H × 3–4′ W, slow, very dense.

• Dwarfs: ‘Hetz Midget’, ‘Danica’, ‘Woodwardii’, ‘Rheingold’ (golden, bronzes in winter).

Planting tip: Set the root flare at or slightly above grade; water deeply and regularly the first two seasons for fastest establishment.