Zumi Calocarpa Crabapple

Full bloom

Malus × zumi 'Calocarpa'

Rosaceae · broadleaf deciduous tree · introduced

Last updated

Quick Facts

Height
20-25 ft (J. Frank Schmidt Crabapple Chart: 20 ft; Missouri Botanical Garden: 20-25 ft)
Spread
20-24 ft (J. Frank Schmidt: 24 ft; Missouri Botanical Garden: 20-25 ft; the gracefully spreading habit means crown often equals or exceeds height)
Growth Rate
Medium (typical malus growth rate; reaches mature size in 20-25 years)
Light
Full Sun (Best Flower Production And Disease Resistance) (Source: Uf/Ifas; Missouri Botanical Garden)
Soil
Well Drained; Tolerates A Wide Range Of Soil Textures (Source: Uf/Ifas; Missouri Botanical Garden)
Water
Moderate
Hardiness
Zone Zones 5–8 (J. Frank Schmidt Crabapple Chart; M. baccata parentage supports Zone 4 cold hardiness but the cultivar is most commonly rated Zone 5)
Bloom Time
Late April to mid-May (Puget Sound); mid-season blooming (source: HortGuide regional interpretation based on Morton Arboretum bloom timing)
Fall Color
Yellow to yellow-bronze; not a primary ornamental feature (source: hortguide editorial based on missouri botanical garden description)
Origin
Cultivar; Malus × zumi is a natural hybrid of Malus baccata
Watch for this season
Fire BlightHigh

Bloom Infection Window

Powdery MildewModerate

Spring Emergence / Primary Infection

Codling mothModerate

Pupation

Phenological Calendar

As of May 13, 2026, Puget Sound stations range from 1906.2 to 2098.2 GDD₃₂. Zumi Calocarpa Crabapple has passed full bloom (1305 GDD₃₂).

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of May 13, 2026
Station GDD₃₂ Current Stage Next To Go
Issaquah / East King 2,098 Full bloom — —
Kent / Auburn 2,089 Full bloom — —
Seattle / UW 2,063 Full bloom — —
Olympia / Tumwater 2,025 Full bloom — —
Tacoma / Puyallup 1,993 Full bloom — —
Bellingham / Whatcom 1,972 Full bloom — —
Sequim / Rain Shadow 1,906 Full bloom — —
Stage GDD32 Typical Window
Beginning of flowering BBCH 61 990 Late April (Puget Sound); mid-season blooming
● Full bloom BBCH 65 NOW 1305 Late April to early May (Puget Sound)

Source: HortGuide regional interpretation based on Morton Arboretum bloom timing About GDD₃₂ →

Season tracker for Kent / Auburn as of May 13, 2026. Predicted dates use 16-day weather forecast through May 29, 2026, then climate normals.

Diseases: Regionally Documented (3)

Diseases: Other Associations (1)

Pests: Regionally Documented (3)

Zumi Calocarpa is one of the older traditional crabapples that has earned its century-plus reputation through reliable performance, and it remains an excellent recommendation for Puget Sound landscapes. The disease resistance profile (Scab Excellent, Fire Blight Excellent, Rust Excellent, Mildew Good per JFS) is among the best of any crabapple in commerce — meeting or exceeding most modern named cultivars on the major pathogens. For PNW landscapes where high spring scab pressure is the norm, this is a meaningful selling point. The 20-25 ft × 24 ft mature size makes Zumi Calocarpa larger than compact cultivars like 'Adirondack' (10 ft spread) or 'Coralcole' (15 ft) — better suited to acreage, parkland, or larger residential yards where the gracefully spreading rounded form can be displayed. The bright red bud-to-white flower contrast at peak bloom and persistent glossy red fruit through winter give the cultivar genuine multi-season ornamental interest. Often used as a pollinizer for fruiting apple orchards because mid-season bloom overlap with commercial varieties is good. Sourcing note: at PNW nurseries, this cultivar is sometimes sold simply as "Redbud Crabapple" — verify the full botanical name (Malus × zumi 'Calocarpa') because straight Malus zumi has meaningfully different characteristics.

— Chris Welch, ISA Certified Arborist

Data Maturity
Structured Multiple sources. Expert review underway.