Plant tomatoes in Southern California between late February and early April for spring harvest, or in late July and August for fall harvest

Southern California's mild winters and long growing season let you plant tomatoes twice a year — something gardeners in colder regions cannot do. The spring window runs from late February through early April, depending on your exact location and how close you live to the coast. The fall window opens in late July and stays open through August. Both windows work because Southern California rarely freezes hard enough to kill tomato plants, and the soil stays warm enough for seeds to germinate and roots to establish.

The exact date matters more than you might think. Plant too early in spring and a late frost can kill seedlings. Plant too late in summer and your tomatoes will still be ripening when October fog rolls in and temperatures drop below 50°F at night — the point where tomato plants stop ripening fruit and start dropping leaves. Knowing your microclimate (whether you live inland, near the coast, or in a valley) narrows the window further.

Key Takeaways

  • Spring planting in Southern California runs from late February to early April, with inland areas starting earlier than coastal zones.
  • Fall planting happens in late July and August so fruit ripens before October fog and cool nights slow the plant down.
  • Soil temperature should reach at least 60°F before planting seeds directly; transplants can go in slightly earlier.
  • Coastal Southern California stays cooler and foggier than inland areas, so coastal gardeners should plant 2 to 3 weeks later in spring and earlier in summer for fall crops.
  • Tomatoes need 6 to 8 weeks of warm weather after planting to produce ripe fruit, so timing the fall crop to finish before October is critical.

Spring planting: late February through early April

In inland Southern California — places like San Diego County's inland valleys, Riverside, or the Inland Empire — you can start seeds or transplants in late February. Soil temperatures at that time usually sit between 55°F and 65°F, which is warm enough for transplants to establish roots without rotting. If you are direct-seeding (planting seeds straight in the ground), wait until soil hits 60°F, which typically happens by mid-March inland.

Coastal Southern California — San Diego proper, Orange County beaches, Los Angeles coastal areas — stays cooler because of marine influence. Soil warms more slowly. Plant transplants in mid-March and seeds in early April. The ocean keeps nighttime temperatures lower even in spring, so planting too early means your seedlings sit in cold soil and grow slowly or rot before they establish.

By early April, nearly all of Southern California is safe for tomatoes. Frost risk drops sharply after mid-March inland and after early April near the coast. If you miss the spring window, you can still plant in May, but you will lose 4 to 6 weeks of growing time, and your harvest will compress into a shorter window in July and August when heat stress can reduce fruit quality.

Fall planting: late July and August

The fall crop is the secret weapon for Southern California tomato growers. Plant in late July or early August, and your tomatoes will produce through September and into October while inland areas are still hot enough for good ripening. The soil is already warm from summer, so seeds germinate fast and transplants establish quickly.

The constraint is the end date, not the start date. Tomatoes need roughly 6 to 8 weeks of warm nights (above 55°F) to ripen fruit. October fog and cooling temperatures slow ripening dramatically. If you plant in late August, you are cutting it close — fruit may still be green when temperatures drop. Plant by early August and you give yourself a comfortable margin. Inland gardeners can push into early August; coastal gardeners should aim for late July.

Fall-planted tomatoes often produce better fruit than spring plantings because they mature in cooler weather, which concentrates flavor and reduces the risk of sunscald (white or yellow patches on fruit from intense summer heat). The trade-off is that you are racing the calendar, so timing matters more than it does in spring.

How soil temperature affects planting dates

Tomato seeds will not germinate reliably below 60°F. Transplants can tolerate slightly cooler soil — 55°F to 60°F — but they grow slowly and risk rotting if soil stays cold and wet. A soil thermometer costs $10 to $20 and removes guesswork. Stick it 4 inches into the ground in the morning, before the sun warms the surface.

In Southern California, soil temperature lags air temperature by 2 to 4 weeks. A warm day in February does not mean the soil is warm. Check the actual soil temperature before planting, especially in spring. By late March inland and early April near the coast, soil is reliably warm enough. In summer, soil stays warm enough for fall planting from late July onward.

Coastal versus inland timing differences

Coastal Southern California (within 5 miles of the ocean) experiences marine layer fog that keeps mornings cool and delays soil warming. Nighttime temperatures stay 5°F to 10°F cooler than inland areas even in summer. This means coastal gardeners should plant spring crops 2 to 3 weeks later than inland gardeners and should start fall crops 1 to 2 weeks earlier.

Inland Southern California (San Diego County inland, Riverside, San Bernardino, Kern County) warms faster in spring and stays hotter in summer. Soil reaches 60°F by mid-March. Nighttime temperatures in summer stay above 60°F through September, giving you more time for fall crops. If you live inland, you can plant spring tomatoes as early as late February and fall tomatoes as late as early August.

If you are unsure whether you are in a coastal or inland microclimate, check your local National Weather Service forecast for nighttime lows in March and September. If March lows stay in the 40s and September lows drop to the 50s by mid-month, you are in a coastal zone. If March lows are in the 50s and September lows stay in the 60s, you are inland.

Frost risk and late-spring cold snaps

Southern California rarely experiences hard freezes, but late-spring cold snaps do happen. A frost in late March or early April can kill young seedlings. Transplants are more vulnerable than established plants because they have not developed deep roots yet. If you plant in late February or early March and a frost warning appears, cover plants with frost cloth or burlap overnight.

The safest approach is to wait until mid-March inland or early April near the coast before planting. At that point, frost risk drops to near zero. If you want to plant earlier and accept the risk, keep frost cloth on hand and monitor the forecast in March.

Choosing between seeds and transplants

Seeds take 6 to 8 weeks to grow into transplant-size seedlings indoors before you move them outside. If you want to direct-seed (plant seeds straight in the ground), you need soil at 60°F or warmer. Transplants can go in at 55°F to 60°F because they are already established. For spring planting, most Southern California gardeners buy transplants from a nursery in late February or early March and plant them out when ready. This skips the indoor seed-starting step and gets you to harvest faster.

For fall planting, you can direct-seed in late July and August because soil is warm. Seeds germinate in 7 to 10 days and seedlings grow fast in warm soil. Direct-seeding saves money and works well for fall crops. If you prefer transplants in fall, start seeds indoors in late June so they are ready to plant in late July.

Frequently Asked Questions

Can I plant tomatoes in December or January in Southern California?

Soil is too cold in December and January — usually 45°F to 55°F — for seeds to germinate or transplants to establish roots. Seedlings planted in cold soil sit dormant and often rot before they grow. Wait until late February inland or mid-March near the coast.

What happens if I plant tomatoes too late in summer?

If you plant after early August, fruit will still be ripening when October fog arrives and nighttime temperatures drop below 55°F. Tomatoes stop ripening in cool weather, leaving you with green fruit that never turns red. Plant by early August to finish ripening before October.

Do I need to start seeds indoors for spring planting?

No. Buy transplants from a nursery in late February or early March and plant them directly in the ground. This is faster and easier than starting seeds indoors. For fall planting, you can direct-seed in late July because soil is warm, or start seeds indoors in late June if you prefer transplants.

How do I know if my soil is warm enough?

Use a soil thermometer inserted 4 inches deep in the morning. Seeds need 60°F or warmer; transplants can tolerate 55°F to 60°F. In Southern California, soil reaches these temperatures by mid-March inland and early April near the coast in spring, and stays warm enough for fall planting from late July onward.

Should I plant different tomato varieties at different times?

Determinate (bush) tomatoes mature faster — 60 to 75 days — and work well for fall planting because they finish before October cooling. Indeterminate (vining) tomatoes take 75 to 85 days and produce longer, so they suit spring planting. Both can grow in either season if you time planting correctly.