Garden PlannerEvidence-aware. Garden with confidence.
Entire healthy mature zucchini plant in a real garden bed, showing growth habit and scale.Primary identification image. 60–90 cm tall, 90–120 cm wide at maturity.

Zucchini

Cucurbita pepo L.

Also called: Courgette, Summer squash, Marrow

Family
Cucurbitaceae
Season
Warm-season annual
Best grown in
Portland, Oregon

A large, bushy, prolific summer squash; two plants feed a household, and each needs a square metre.

Safety: Rarely, bitter fruit (cucurbitacins) should not be eaten.

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Life cycle & growth stages

  1. 1. SeedSow 2–3 cm deep in warm soil.
  2. 2. SeedlingLarge cotyledons in 5–10 days.
  3. 3. TransplantSet out after frost, 90 cm apart.
  4. 4. FloweringMale flowers on long stems; female flowers with a small fruit behind.
  5. 5. Developing fruitFruit doubles in size every few days.
  6. 6. Harvest ready15–20 cm long, glossy.
  7. 7. HarvestCut every 1–2 days.

Growth stages are ordered chronologically; timing varies with cultivar, temperature, light and care.

Planting calendar for Portland, Oregon

Start indoors 3–4 weeks before last frost; transplant 1–3 weeks after last frost; direct sow 1–4 weeks after last frost; 45–60 days to maturity from sowing. Windows are derived from the region's average frost dates (last Apr 5, first Nov 5) and are estimates until you confirm your own dates in the calendar.

ZucchiniCucurbita pepo
PlantStart indoorsDirect sowAutumn sowTransplantTendHarvest
ZucchiniMar 8–Mar 15 (estimate)Apr 12–May 3 (estimate)—Apr 12–Apr 26 (estimate)May 3–May 27 (estimate)May 27–Nov 5 (estimate)
  • Start seeds indoors: Mar 8 – Mar 15
  • Transplant outdoors: Apr 12 – Apr 26
  • Direct sow: Apr 12 – May 3
  • Tend and monitor: May 3 – May 27
  • Harvest: May 27 – Nov 5

Spacing & support

In-row 60–90 cm; rows 90–120 cm. Planner footprint: 6 cells of 30 cm.

Side-profile diagram of mature zucchini: canopy 60–90 cm tall, 90–120 cm wide, medium root zone, support and harvest-access envelope.

Soil & water

Soil
Rich, well-drained soil with compost
pH
6–7
Fertility
high
Water
Deep watering at the base; avoid wetting leaves.
Frost
tender; killed by frost

Support & training

No support structure needed.

Zucchini mid-season before harvest, showing branching, vining, rosette or upright habit and space occupied.

Harvest signs

  • Fruit 15–20 cm with glossy skin
  • Flower still attached or just withered
  • Cut with a knife; do not twist
Zucchini at harvest readiness, showing the visual cues: fruit 15–20 cm with glossy skin; flower still attached or just withered.

Common problems

Pests: squash bugs, cucumber beetles, squash vine borer, aphids

Diseases: powdery mildew, bacterial wilt, blossom end rot (physiological)

Appearance alone is not a diagnosis; confirm with a regional extension guide.

Side-by-side: healthy zucchini leaf or fruit and an example of powdery mildew.

Container growing

  • Minimum 40 L (40 cm deep)
  • Use quality potting mix and water more frequently
  • One plant per 40 L container; compact cultivars are better.
Mature zucchini in a correctly sized container (40 L or more) with drainage visible.

Companion overview

4 reviewed relationship records (evidence: low).

Supported or conditional

Winter squash

Avoid or separate

None with evidence

Traditional claims only: Borage.

2 popular pairings reviewed with no verified relationship.

Full companion profile

Crop rotation

Avoid planting zucchini or other squash family crops in the same spot for 2 years. Rotation is about previous seasons, not about live neighbours.

Year 1Year 2Year 3CucurbitaceaeOther familyOther familyback after 2+ years

Shared risks in Cucurbitaceae: powdery mildew, bacterial wilt, striped and spotted cucumber beetles.

Crop rotation hub

Sources, reviewer & update

Sources

Reviewer: Garden Planner editorial team (pending independent horticultural review)

Last reviewed: August 15, 2026 · version 1

Found an error or have feedback? Let us know.

Growing zucchini

Zucchini is sown after the last frost in warm soil and crops within 45–60 days. Plants are bushy rather than vining but still spread 90–120 cm; give them the edge of a bed so the large leaves do not shade neighbours.

Zucchini seed beside a ruler or coin for scale.
Zucchini seedling at cotyledon and first-true-leaf stage, in soil, distinguishable from common weeds.
Zucchini mid-season before harvest, showing branching, vining, rosette or upright habit and space occupied.

Pick fruit at 15–20 cm every other day; a fruit missed for a week becomes a marrow and slows production. Poor fruit set in early summer is usually a shortage of pollinators or of female flowers, not disease.

Two or more mature zucchini plants with a tape measure showing in-row spacing (60–90 cm).
Zucchini flowers: male and female flowers side by side.
Immature fruit of zucchini developing on the plant.

Squash bugs, cucumber beetles and, in North America, squash vine borer are the main pests; powdery mildew coats leaves from late summer. Rotate with other cucurbits.

Edible parts and safety

Edible: fruit, flowers. Rarely, bitter fruit (cucurbitacins) should not be eaten.

Hands or tool harvesting zucchini correctly (cut, pull, twist or pick) without damaging the plant.

Pests and diseases

Common pests: squash bugs, cucumber beetles, squash vine borer, aphids. Common diseases: powdery mildew, bacterial wilt, blossom end rot (physiological). These vary by region; a photograph is an example, not a diagnosis. See the pest and disease guides and your local extension service.

squash bugs on zucchini, with a wider damage-context view.

Timeline

Season timeline for zucchini: sowing, transplanting, flowering, harvest and bed occupancy aligned to frost dates.Text alternative: Start seeds indoors Mar 8–Mar 15; Transplant outdoors Apr 12–Apr 26; Direct sow Apr 12–May 3; Tend and monitor May 3–May 27; Harvest May 27–Nov 5.

Related plants

See also: Cucurbitaceae family page · crop rotation · regional calendar · guides

Our Methodology & Sources

We synthesize peer-reviewed research, university extension publications, and trusted horticulture resources. Our evidence levels help you understand how strong the science is behind the guidance.

Evidence tiers

Supported evidenceConsistent results from multiple robust studies
Traditional claimHistorical use reported, limited scientific support
Context dependentMixed or variable results across conditions
No verified relationshipNo reliable evidence identified

Primary source types

  • Peer-reviewed journal articles
  • University extension publications
  • Government & research institute reports
  • Systematic reviews & meta-analyses

Last updated

August 24, 2026

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