Rose

Hibiscus syriacus

Malvaceae · broadleaf deciduous shrub · introduced

Last updated May 11, 2026

Rose of Sharon (Hibiscus syriacus, Malvaceae) is an erect, vase-shaped deciduous shrub from China and India (not Syria, despite the misleading epithet), reaching 8 to 12 feet tall and 6 feet wide. Large, trumpet-shaped, five-petaled flowers in blue, lavender, pink, purple, red, and white tones bloom prolifically from July through October. Each flower is short-lived (one day) but the display is continuous on current-season growth.

Rose of Sharon grows in full sun to part shade on moist, well-drained soil (pH 4.5 to 8.5), hardy in Zones 5a to 8b. It tolerates deer browse, drought, clay soil, and black walnut proximity. It blooms on new wood; prune in late winter to early spring. Disease pressure is notable, with 11 documented associations including powdery mildew, crown gall, and rust. Pest pressure is among the highest in the knowledge base: 27 documented associations including aphids, thrips, and fall webworm.

Plant Profile

Size & Form

Height

8–12 ft

Spread

6 ft

Growth Rate

Medium

Site Requirements

Light

Full Sun to Part Shade

Soil Drainage

Moist

Soil pH

4.5-8.5

Water

Moderate

Drought Tolerance

Moderate to high

Hardiness

Zones 5a–8b

Ornamental Interest

Bloom Time

June to October

Fall Color

Yellow

Origin

China and India

Powdery MildewHigh

Active Conidial Spread

RustHigh

Uredinial Stage (Summer)

AphidHigh

Peak Population & Dispersal

Fall webwormHigh

Larval Feeding & Web Building

+ 5 more — see full disease and pest lists below

Diseases: Regionally Documented (10)

Chlaropsis thielavioides Black Mold [NOTE: Diplocarpon rosae causes black spot on roses (Rosa... Black Spot Botrytis Bud and Twig Blight Kalmusia coniothorium Brand canker Coniothyrium wernsdorffiae and Paraconiothyrium fuckelii Common canker Rhizobium radiobacter (formerly Agrobacterium tumefaciens) Crown Gall Multiple obligate oomycetes (Peronosporaceae); species ar... Downy Mildew Multiple obligate biotrophic fungi (Erysiphales: Erysipha... Powdery Mildew Multiple genera (Melampsoridium, Thekopsora, Naohidemyces... Rust Raspberry bushy dwarf virus and related viruses Virus

Phenological Calendar

As of June 3, 2026, Puget Sound stations range from 2435.5 to 2672.8 GDD₃₂. Rose typically reaches beginning of flowering at 3976 GDD₃₂, predicted around Jul 18.

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of Jun 3, 2026

Station	GDD₃₂	Current Stage	Next	To Go
Issaquah / East King	2,673	Pre-season	Beginning of flowering	1,303
Kent / Auburn	2,665	Pre-season	Beginning of flowering	1,311
Seattle / UW	2,610	Pre-season	Beginning of flowering	1,366
Olympia / Tumwater	2,570	Pre-season	Beginning of flowering	1,407
Tacoma / Puyallup	2,535	Pre-season	Beginning of flowering	1,441
Bellingham / Whatcom	2,533	Pre-season	Beginning of flowering	1,443
Sequim / Rain Shadow	2,436	Pre-season	Beginning of flowering	1,541

View full calendar (1 stages)

Stage	GDD₃₂	Typical Window	What to Look For
○ Beginning of flowering BBCH 61 NEXT	3976	— est. Jul 18 (avg)	First open blossoms visible on early branches

Regional estimate

Range: 3165–3613 GDD₃₂ (6yr)

Source: UMD: extension.umd.edu) About GDD₃₂ →

Season tracker for Kent / Auburn as of Jun 3, 2026. Predicted dates use 16-day weather forecast through Jun 19, 2026, then climate normals.

Cultivars (3)

'Some Selections'

Common name: Rose of Sharon Shrub Althea

'Variegata'

Common name: Variegated Rose of Sharon; Mature height: 5–8 ft

Hardy to USDA Zone 5

'Notwoodone'

Data Maturity

Structured Multiple sources. Expert review underway.