Summer Squash / Zucchini

Cucurbita pepo

Cucurbitaceae · annual · introduced

Last updated May 23, 2026

Quick Facts

Height

1-3 ft (bush types); vines to 10+ ft

Spread

3-6 ft (bush types); 10-15 ft (vining types)

Growth Rate

Fast

Light

Full Sun

Soil

Well Drained

Water

Moderate

Hardiness

Zones 3–11 (grown as annual)

Bloom Time

June-September (after transplant)

Fall Color

N/a (annual; killed by first frost)

Origin

North America (Mexico, southern United States)

Damping-offHigh

Spring Sowing - Preemergence Damping-off Risk

Downy MildewHigh

Spring New Growth - Early Infection Window

Verticillium WiltHigh

Root Colonization Period

Powdery MildewModerate

Spring Emergence / Primary Infection

Diseases: Regionally Documented (8)

Multiple obligate biotrophic fungi (Erysiphales: Erysipha... Powdery Mildew Multiple obligate oomycetes (Peronosporaceae); species ar... Downy Mildew Several soilborne Damping-off Verticillium dahliae Verticillium Wilt Sclerotinia Stem Rot (White Mold) Pseudomonas syringae pv. syringae (bacterial form, most c... Angular Leaf Spot Blossom-end Rot Pollination Failure

Pests: Regionally Documented (5)

Anasa tristis Squash Bug Diabrotica undecimpunctata Western Spotted Cucumber Beetle Slugs and Snails Spider Mites Aphids

Phenological Calendar

View full calendar (7 stages)

Stage	Typical Window	What to Look For
Transplant / direct seed BBCH 00	Jun 1-Jun 20	Soil consistently above 65°F
Emergence / establishment BBCH 09	Jun 10-Jul 1	Cotyledons or first true leaves expanding
First male flowers BBCH 61	Jul 1-Jul 20	First large yellow male flowers open on long stems
Female flowers / fruit set BBCH 65	Jul 10-Aug 1	Female flowers (with swollen ovary at base) opening; pollinators active
Harvest (summer squash) BBCH 87	Jul 20-Oct 1	Zucchini 6-8 inches; harvest every 2-3 days
Powdery mildew onset	Aug 10-Sep 15	White powdery patches on older leaves; typically mid-August
Frost kill BBCH 97	Oct 15-Nov 15	Foliage blackened by first frost

Cultivars (3)

'Dark Star'

Zucchini. Dark green, compact bush habit. Early and prolific. Good powdery mildew tolerance.

Good choice for small gardens in PNW

'Dunja'

Zucchini. Compact bush, dark green fruit. Strong powdery mildew resistance (PM-tolerant).

Recommended for PNW where PM is inevitable

'Costata Romanesco'

Italian heirloom zucchini. Ribbed, gray-green fruit with exceptional nutty flavor. More vining habit.

Popular with PNW gardeners for flavor

Data Maturity

Baseline Extension data. Expert review underway.