Eastern Arborvitae

Thuja occidentalis

Cupressaceae · coniferous tree · native

Last updated March 9, 2026

Data Maturity Structured

This profile synthesizes data from multiple published sources. Expert field review is in progress.

Eastern arborvitae (American arborvitae) is a conifer native to eastern and central North America. It reaches 40 ft with a conical form, fine foliage texture, and brown cones. It has reddish-brown bark fissured into narrow ridges and grows as a single-stem tree.

Eastern arborvitae is hardy in zones 4a-9b and tolerates sun to part shade with wet-tolerant, alkaline soils (pH 5.2-7.0). It grows slowly with low maintenance and is notably tolerant of clay, wet soil, and urban conditions. The essential oil in foliage is poisonous if ingested in large doses.

Quick Facts

Height

40 ft

Spread

16 ft

Growth Rate

Slow

Light

Sun to Part Shade

Soil

Wet Tolerant

Water

Moderate

Hardiness

Zone Zones 4a–9b

Bloom Time

Non-flowering

Origin

USDA Zone (2)3 The species is native from eastern to

Phenological Calendar

As of April 23, 2026, Puget Sound stations range from 1434.4 to 1592.7 GDD₃₂. Eastern Arborvitae typically reaches new growth flush at 1596 GDD₃₂, predicted around Apr 27.

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 23, 2026

Station	GDD₃₂	Current Stage	Next	To Go
Issaquah / East King	1,593	Pre-season	New growth flush	3
Seattle / UW	1,554	Pre-season	New growth flush	42
Kent / Auburn	1,537	Pre-season	New growth flush	59
Olympia / Tumwater	1,505	Pre-season	New growth flush	92
Bellingham / Whatcom	1,483	Pre-season	New growth flush	113
Tacoma / Puyallup	1,472	Pre-season	New growth flush	124
Sequim / Rain Shadow	1,434	Pre-season	New growth flush	162

Stage	GDD₃₂	Typical Window	What to Look For
○ New growth flush BBCH 11 NEXT	1596	Feb 15-Mar 15 est. Apr 27 (forecast)	Lighter-colored new growth visible at branch tips
Bloom start BBCH 61	—	Apr 1-Apr 30	First open flowers visible
Bloom end / petal fall BBCH 69	—	Apr 15-May 15	Last petals falling; flower structures fading
Fruit/seed development BBCH 71	—	Jun 1-Aug 31	Fruit or seed structures forming; fruit color: brown
Fruit/seed maturity BBCH 85	—	Sep 1-Nov 30	Fruit fully colored and ripened; seed dispersal may begin

GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? Hover over GDD values for source details. Season tracker for Kent / Auburn as of Apr 23, 2026. Predicted dates use 16-day weather forecast through May 10, 2026, then climate normals.

Diseases (12)

Black Flagging Symptom category — not a single disease Root Rot Seiridium cardinale Seiridium Canker Diaporthe vaccinii or Diplodia tip blight agents Tip Blight Diaporthe vaccinii Twig Blight Fungal growth Coniophora Growth Didymascella thujina Leaf Blight (Keithia Blight) Postia sericiomollis Pencil Rot (Brown Pocket Rot) Fomitopsis officinalis, Porodaedalea pini, and other wood... Stem Decay Perreniporia subacida Yellow Root Rot Phytophthora lateralis Port Orford cedar root rot Fungal agents (multiple) Leaf Blight

Pests (14)

Various (Coleoptera, Lepidoptera) Borer Otiorhynchus spp. Root weevil Coccoidea Scale insect Tetranychidae Spider mite Scale Berckmann's Blight Cedar Flagging Shoot Tip Dieback Argyresthia cupressella Cypress tip moth Various (Buprestidae, Scolytinae) Flat Headed And Shothole Borers Carulaspis juniperi Juniper scale Juniper fall-webworm Various (Agromyzidae, Gracillariidae, Tenthredinidae) Leafminer Physokermes piceae Spruce bud scale

Cultivars (5)

'Golden Globe'

Common name: Golden Globe Arborvitae; Mature height: 3–5 ft

Hardy to USDA Zone 3

'Hetz Midget'

Common name: Hetz Midget Arborvitae; Mature height: 3–4 ft

Hardy to USDA Zone 3

'Rheingold'

Common name: Rheingold Arborvitae; Mature height: 4–5 ft

Hardy to USDA Zone 3

'Yellow Ribbon'

Common name: Yellow Ribbon Arborvitae; Mature height: 8–10 ft

Hardy to USDA Zone 3

'Smaragd'