PlantAlong

When to plant tomatoes in zone 7a

Transplant outdoors around Apr 30. That is 2 weeks after zone 7a's median last frost, Apr 161. Across most of zone 7a that date falls between Apr 18 and May 12.

Why a range: zone 7a is defined by winter lows, not frost dates. Its ZIP codes have median last frosts from Apr 4 to Apr 282, so a single zone date can be weeks off for you. The rule comes from Colorado State University Extension, written for CO and applied here to zone 7a's frost dates.

Last reviewed
Stations
865
ZIP codes
3,807
Photo: Thể Phạm / Pexels
These dates use the typical last frost for the whole zone. Your ZIP code gives a closer answer.
  1. Start indoorsOregon State, central OR
  2. Transplant outdoorsColorado State
  • Start indoors
  • Plant outdoors
  • Range across the zone
  • Frost-free season (median)
  • Spring frost risk (90% to 10%)
  • Fall frost risk (10% to 90%)
Figure 1. Tomatoes in zone 7a. Dark bars: at the zone's median frost dates. Pale bars: across most of the zone's ZIP codes. Hatched blue: where the zone's last and first frosts fall.
Start seeds indoors
Feb 208 weeks before last frost (Oregon State, central OR)
Transplant outdoors
Apr 30range Apr 18 – May 12
First harvest, roughly
Jul 465 days from transplant1

Five digits. The calendar is computed on your device.

What each source says, applied to zone 7a

The same frost dates give different answers depending on whose rule you follow. These are all the published rules we hold for tomatoes, worked out at zone 7a's median frost dates.

Table 1. Tomatoes rules from every source, at zone 7a's median last frost (Apr 16) and first frost (Oct 25).
SourceWhatRuleZone 7a median
Colorado State1Used aboveTransplant outdoors2 weeks after last frostApr 30
Utah State3Transplant outdoors2 weeks after last frostApr 30
Oregon State, central OR4Transplant outdoorsOn the last frostApr 16
Oregon State, central OR4Used aboveStart indoors8 weeks before last frostFeb 20
Texas A&M (E-502)5Transplant outdoors1-8 weeks after last frostApr 23 – Jun 11
Texas A&M (E-502)5Plant for fall12-14 weeks before first frostJul 19 – Aug 2

Frost across zone 7a

  1. Last spring frostmedian Apr 16
  2. First fall frostmedian Oct 25
  • Frost-free season (median)
Figure 2. Frost dates across zone 7a, from 865 NOAA stations matched to 3,807 ZIP codes.

Planting tomatoes with others

  • Basil Tested in a study Claims: basil raises combined yield, improves tomato flavour and masks tomatoes from thrips and hornworms. Garden-scale trials found no consistent flavour effect and mixed yield results.6667788910
  • Marigold Tested in a study French marigold grown alongside tomato slowed glasshouse whitefly build-up (airborne limonene). Marigold grown before tomato reduced root-knot nematode galling in the following tomato crop.9111112121210
  • Potatoes Extension guidance Shared late blight: the pathogen overwinters mainly on infected potato tubers and spreads by wind to nearby tomatoes.13131010

Sources

  1. Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 2024. Retrieved 2026-11-02.
  2. NOAA National Centers for Environmental Information, U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), 2021. Retrieved 2026-11-02.
  3. Utah State University Extension, Suggested Vegetable Planting Dates for Utah, January 2018; revised May 2025. Retrieved 2026-11-02.
  4. Oregon State University Extension Service, When to start seeds indoors in central Oregon, reviewed 2024. Retrieved 2026-11-02.
  5. Texas AgriLife Extension Service, The Texas A&M System, Texas Home Vegetable Gardening Guide (E-502), 2/09. Retrieved 2026-11-02.
  6. West Virginia University, Plant and Soil Science (Ph.D. thesis); record on Organic Eprints, Yield, pest density, and tomato flavor effects of companion planting in garden-scale studies incorporating tomato, basil, and Brussels sprout, 2004 (deposited 19 Dec 2005). Retrieved 2026-11-02.
  7. Meeting abstract (ASA-CSSA-SSSA 2003 annual meetings abstracts collection, mirrored by Prince of Songkla University library), Do Tomatoes Love Basil But Hate Brussels Sprouts? Evaluating Popular Companion Planting Claims in Garden-Scale Studies (NE_05-bomford156693-oral), 2003. Retrieved 2026-11-02.
  8. Penn State Extension, Herbs Make Good Plant Partners and Companions, Updated April 22, 2026. Retrieved 2026-11-02.
  9. PLOS ONE 14(3): e0213071, Companion planting with French marigolds protects tomato plants from glasshouse whiteflies through the emission of airborne limonene, March 1, 2019. 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 31(4S):709-714 (Society of Nematologists); PMC2620405, Effect of Temperature on Suppression of Meloidogyne incognita by Tagetes Cultivars, December 1999. 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. Washington State University Extension (HortSense), Tomato: Late blight (HortSense fact sheet), reviewed Last review date: 2026-08-28. Retrieved 2026-11-02.