Common Pear
Pyrus communis
Rosaceae · broadleaf deciduous tree · introduced
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Growing pears in the Puget Sound lowlands means managing fire blight. The bacterium (Erwinia amylovora) thrives in our wet springs, entering through blossoms during warm rain events. Cultivar choice is the first line of defense: 'Bartlett' and 'Forelle' are highly susceptible; 'Harrow Delight' and 'Moonglow' have useful resistance. The trees bloom early enough (999 GDD base 32 for bud break) that late frost is a real risk in March. Scab is the second disease to watch, worst in springs with extended wet periods. On the pest side, pear psylla is chronic and pear slug (actually a sawfly) defoliates young trees. Site in full sun with air circulation; pruning for an open canopy reduces disease pressure. Pick fruit mature but hard and ripen off the tree at 60-65 degrees. Winter pears (Bosc, Comice) need cold storage before ripening.
— Chris Welch, ISA Certified Arborist
Pyrus communis (Rosaceae) is a deciduous fruit tree native to Europe and western Asia. It grows rapidly to about 50 feet tall with a pyramidal form. White flowers appear in March to April, followed by the familiar pear fruit. Dark green, glossy leaves turn variable colors in autumn.
Common pear grows in full sun on well-drained, fertile soil (pH 5.2 to 6.7). Most cultivars require cross-pollination. The species carries heavy pest and disease pressure: 27 diseases and 15 pests are documented, with fire blight being the most devastating. Pear psylla is the primary insect pest. The species serves as a host for numerous butterflies. Hardy in Zones 5a to 8b.
Quick Facts
Phenological Calendar
As of April 23, 2026, Puget Sound stations range from 1434.4 to 1592.7 GDD₃₂. Common Pear has passed 'leaf emergence' (1144 GDD₃₂).
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 | 'Leaf emergence' | — | — |
| Seattle / UW | 1,554 | 'Leaf emergence' | — | — |
| Kent / Auburn | 1,537 | 'Leaf emergence' | — | — |
| Olympia / Tumwater | 1,505 | 'Leaf emergence' | — | — |
| Bellingham / Whatcom | 1,483 | 'Leaf emergence' | — | — |
| Tacoma / Puyallup | 1,472 | 'Leaf emergence' | — | — |
| Sequim / Rain Shadow | 1,434 | 'Leaf emergence' | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Bud break' BBCH '07' | 999 | '' |
| 'Flower buds visible' BBCH '51' | 999 | '' |
| 'First bloom' BBCH '61' | 1117 | '' |
| ● 'Leaf emergence' BBCH '11' NOW | 1144 | '' |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? GDD₃₂ thresholds from USA National Phenology Network citizen science observations (WA+OR). Season tracker for Kent / Auburn as of Apr 23, 2026. Predicted dates use 16-day weather forecast through May 10, 2026, then climate normals.