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Zucchini

When to start, transplant and harvest zucchini, as 5 university extension services put it, and what that means in each zone.

Family
Cucurbitaceae5
Type
Squash family
Rules
8
Last reviewed
Garden experts do not always agree, so I show every rule side by side.

Five digits. The calendar is computed on your device.

Spring timing, source by source

Every rule counts from the last spring frost, so the same rule gives different dates in different gardens. Here are the rules themselves before any dates are worked out.

  1. Colorado StateSow outdoors
  2. Utah StateSow outdoors
  3. Oregon State, central ORTransplant outdoors
  4. Oregon State, central ORStart indoors
  5. Texas A&M (E-502)Sow outdoors
  • Plant outdoors
  • Start indoors
Figure 1. How each extension source times zucchini in spring, in weeks before or after the last frost. Sources disagree; each bar is one publication's rule, shown as written.

Fall timing, source by source

Fall rules count from the first fall frost.

  1. Texas A&M (E-502)Plant for fall
  • Plant outdoors
Figure 2. How each extension source times zucchini in fall, in weeks before or after the first frost. Rules written for warm states sit weeks earlier than those for cold ones.
Table 1. Planting rules for zucchini, as published.
SourceWritten forWhatWhen
Colorado State1COSow outdoorsOn the last frost
Utah State2UTSow outdoorsOn the last frost
Oregon State, central OR8central OregonTransplant outdoors2 weeks after last frost
Oregon State, central OR8central OregonStart indoors1 weeks before last frost
Texas A&M (E-502)4TXSow outdoors1-4 weeks after last frost
Texas A&M (E-502)4TXPlant for fall12-15 weeks before first frost
Nebraska (G1343)9NEPlant for fallCount back days to maturity + 14-day fall factor (+14 for tender crops) from the first frost

Zucchini by hardiness zone

Applied to the frost records of every ZIP in each zone. The zone median is a starting point; your own station can be weeks earlier or later.

Table 2. Outdoor planting for zucchini by zone, using the Oregon State, central OR rule. Linked zones have their own page.
ZoneWhatZone medianAcross most of the zone
4aTransplant outdoorsMay 26May 19 – Jun 7
4bTransplant outdoorsMay 22May 15 – Jun 8
5aTransplant outdoorsMay 17May 10 – Jun 3
5bTransplant outdoorsMay 15May 5 – May 31
6aTransplant outdoorsMay 12Apr 30 – May 24
6bTransplant outdoorsMay 6Apr 24 – May 17
7aTransplant outdoorsApr 30Apr 18 – May 12
7bTransplant outdoorsApr 19Apr 13 – May 1
8aTransplant outdoorsApr 12Apr 3 – Apr 21
8bTransplant outdoorsMar 31Mar 20 – Apr 15
9aTransplant outdoorsMar 16Mar 1 – Apr 1

Growing facts

Table 3. Each value as one source states it. Sources measure differently, so values are not averaged.
FactValueSource
Frost tolerancetenderColorado State1
Frost tolerancetenderUtah State2
Frost tolerancetenderPurdue (HO-66)3
Minimum soil temperature60°FColorado State1
Best soil temperature90°FColorado State1
Days to germinate3-12 daysColorado State1
Days to germinate4-6 daysTexas A&M (E-502)4
Days to maturity50 days from plantingColorado State1
Days to maturity50-60 days from plantingTexas A&M (E-502)4
Days to maturity40-50 days from seedUF/IFAS Florida5
Days to maturity60-90 days from plantingArizona (AZ1005)6
Spacing36-48 in apart each wayColorado State1
Spacing18-36 in in the row, rows 36-60 in apartTexas A&M (E-502)4
Spacing12-24 in in the row, rows 36 in apartUF/IFAS Florida5
Heat limit90°Fpurdue-hot-weather7

Companions, and how sure anyone is

  • Marigold · Disputed Tested in a study

    Tradition lists marigold as a squash companion (no reason given). Field tests of squash (Cucurbita pepo) intercropped with French marigold found no consistent nematode effect.1011111212

    UC chart (tradition) lists marigold as compatible with squash. Powers et al. 1993 found no consistent nematode differences under squash and cucumber intercropped with marigold; UF/IFAS ENY-056 says that intercrop was less productive than monoculture. Sources say "squash" and "Cucurbita pepo", not zucchini by name. As a preceding cover crop (2+ months before), marigold can reduce root-knot nematodes.

  • Blue Hubbard squash · Trap crop Tested in a study

    A border of Blue Hubbard squash draws striped cucumber beetles away from the summer squash it encircles; the border is sprayed when beetles arrive.131313141413

    Connecticut experimental plots used yellow summer squash, not zucchini by name: over 94% of cucumber beetles were on the Blue Hubbard perimeter; border sprays cut beetles on the unsprayed main crop by up to 93% and squash vine borer by 88%. A six-farm demonstration (Boucher & Durgy 2004) is grower-reported, not a replicated trial. Needs border spraying; farm scale.

  • Potatoes · Avoid together Traditional pairing10

    The chart says "squash", not zucchini by name.

  • Nasturtium · Helps Traditional pairing10

    The chart says "squash", not zucchini by name.

Traditional pairings come from a UC Master Gardener chart that traces to the UC Davis Edible Landscaping Handbook and ATTRA. The chart gives no reasons, and we found no trial of these pairs; treat them as garden lore.

All zucchini companions, with sources · The full companion chart

Sources

  1. Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 2024. Retrieved 2026-11-02.
  2. Utah State University Extension, Suggested Vegetable Planting Dates for Utah, January 2018; revised May 2025. Retrieved 2026-11-02.
  3. Purdue Extension, The Fall Vegetable Garden (HO-66-W), reviewed September 2019. Retrieved 2026-11-02.
  4. Texas AgriLife Extension Service, The Texas A&M System, Texas Home Vegetable Gardening Guide (E-502), 2/09. Retrieved 2026-11-02.
  5. University of Florida, IFAS Extension (Department of Horticultural Sciences), Florida Vegetable Gardening Guide (SP 103 / VH021), Original December 1999; revised October 2015, January 2016, May 2018, September 2020, September 2021, and June 2025. Retrieved 2026-11-02.
  6. The University of Arizona Cooperative Extension, Vegetable Planting Calendar for Maricopa County (AZ1005), reviewed This information has been reviewed by University faculty.. Retrieved 2026-11-02.
  7. Purdue University, Indiana Yard and Garden (Purdue Consumer Horticulture), Hot Weather Is Tough on Plants Too!, reviewed Page last modified October 26, 2016. Retrieved 2026-11-02.
  8. Oregon State University Extension Service, When to start seeds indoors in central Oregon, reviewed 2024. Retrieved 2026-11-02.
  9. University of Nebraska–Lincoln Extension, Fall Vegetable Gardening (NebGuide G1343), Revised March 2012. Retrieved 2026-11-02.
  10. University of California Agriculture and Natural Resources (UCCE Master Gardener Program), Companion Planting Chart: Companion planting in the vegetable garden, File dated 2023-09 in URL path; no date printed. Retrieved 2026-11-02.
  11. Journal of Nematology 25(4):666-673 (Society of Nematologists); FLVC journal host, Effects of Mixed Cropping on a Soil Nematode Community in Honduras, 1993. Retrieved 2026-11-02.
  12. University of Florida, IFAS Extension (Entomology and Nematology Department), Marigolds (Tagetes spp.) for Nematode Management (ENY-056), reviewed Reviewed November 2019; page footer "Reviewed: 01/2024". Retrieved 2026-11-02.
  13. University of Vermont Extension, Vermont Vegetable and Berry Program, Perimeter Trap Cropping: A Novel Approach to Insect Pest Control, July 2004. Retrieved 2026-11-02.
  14. Journal of Extension 42(5), Article 13, Demonstrating a Perimeter Trap Crop Approach to Pest Management on Summer Squash in New England, October 2004. Retrieved 2026-11-02.