Norway Maple
Acer platanoides
Sapindaceae · broadleaf deciduous tree · introduced
Last updated
Norway maple is a common street and shade tree in the Puget Sound lowlands but it has fallen out of favor for good reason. It leafs out early and holds leaves late, casting dense shade that suppresses everything underneath, including lawn. The shallow, aggressive root system heaves sidewalks and outcompetes neighboring plants for water. It self-seeds prolifically and is considered invasive in several states. The disease profile mirrors other maples (tar spot, powdery mildew, anthracnose) and all of these are cosmetic. The real issue with Norway maple is ecological: it displaces native maples and suppresses understory diversity. For new plantings, there are better options. If you have an existing healthy Norway maple providing shade, it is a functional tree, but do not plant more of them.
— Chris Welch, ISA Certified Arborist
A large deciduous tree from continental Europe, reaching 50 feet tall and 40 to 50 feet wide with a dense, rounded canopy and fast growth (35 feet at 20 years). Leaves are broad, five-lobed, and exude milky white sap from the petiole when snapped, distinguishing it from all native maples. Flowers are upright, yellow-green clusters appearing before leaves in March to April. Fall color is bronze, gold, red, and yellow. The canopy is dense enough to suppress virtually all understory growth, and the prolific seeds germinate aggressively. Classified as having weed potential in multiple databases.
Hardy to Zone 4a. Sun to part shade. Adaptable drainage and soils (pH 4.8 to 7.2); tolerates drought, salt, and urban conditions. Moderate root depth (40 inches). Increasingly recognized as invasive across North America: escapes cultivation readily, outcompetes native understory through dense shade and early leaf-out. Nine cultivars are in the trade: 'Crimson King' (purple foliage, 40 x 35 feet), 'Crimson Sentry' (compact, deep purple, 25 x 15 feet), 'Deborah' (reddish-purple, 45 x 40 feet, Zone 3b), 'Drummondii' (variegated, cream-margined, 30 to 40 feet), 'Globosum' (dense globe, 15 x 18 feet), 'Princeton Gold' (bright yellow, 35 x 30 feet), 'Schwedleri' (purplish-red, 40 to 50 feet, Zone 3a), 'Emerald Queen' (deep green, 50 x 40 feet), and 'Columnare' (narrow, 35 x 15 feet). Nineteen diseases and fifteen pests documented.
Quick Facts
Phenological Calendar
As of April 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂. Norway Maple has passed 'full bloom' (825 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,181 | 'Full bloom' | — | — |
| Seattle / UW | 1,171 | 'Full bloom' | — | — |
| Kent / Auburn | 1,111 | 'Full bloom' | — | — |
| Olympia / Tumwater | 1,106 | 'Full bloom' | — | — |
| Bellingham / Whatcom | 1,101 | 'Full bloom' | — | — |
| Tacoma / Puyallup | 1,075 | 'Full bloom' | — | — |
| Sequim / Rain Shadow | 1,070 | 'Full bloom' | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 754 | '' |
| ● 'Full bloom' BBCH '65' NOW | 825 | '' |
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 3, 2026. Predicted dates use 16-day weather forecast through Apr 19, 2026, then climate normals.