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 warms up quickly in both seasons.

The key is soil temperature, not air temperature. Tomato seeds and transplants need soil at least 60°F to germinate or establish roots, and they grow much faster when soil hits 70°F or warmer. In inland Southern California valleys, soil reaches 70°F by mid-March. Coastal areas stay cooler and may not hit that mark until April. If you plant too early into cold soil, seeds rot and transplants sit dormant for weeks, wasting time.

Key Takeaways

  • Spring planting in Southern California runs from late February in inland areas to early April near the coast, timed to when soil reaches 70°F.
  • Fall planting begins in late July and August, giving tomatoes time to produce fruit before the first frost arrives in November or December.
  • Check your soil temperature with a straightforward soil thermometer before planting—do not guess based on air temperature alone.
  • Coastal gardens stay 10 to 15 degrees cooler than inland valleys, so adjust your planting dates later if you live near the ocean.
  • Determinate (bush) tomatoes mature faster than indeterminate (vining) types, so choose determinate varieties for fall planting to beat the frost.

Spring planting: late February to early April

Spring is the main tomato season in Southern California. Most gardeners plant in March, when soil has warmed from winter rains and the risk of a hard frost has dropped sharply. In inland areas—the San Fernando Valley, inland Orange County, San Diego County inland—soil often reaches 70°F by mid-March. Coastal gardens and areas within five miles of the ocean stay cooler and may not hit 70°F until late March or early April.

You can start planting as early as late February if you use black plastic mulch or row covers to warm the soil faster, but this adds work and is not necessary. A simpler approach is to wait until mid-March in inland areas or early April near the coast, plant your transplants, and let the warming soil do the work. Tomatoes planted in warm soil establish roots quickly and start producing fruit by June or July.

Spring-planted tomatoes have the whole summer ahead of them. They grow through the heat of July and August and keep producing until the first frost arrives—usually in November or December in most of Southern California, or even later in frost-free zones near the coast. This long season is why spring planting is so popular.

Fall planting: late July and August

Fall planting is the secret weapon for Southern California gardeners. You plant in late July or August, when soil is still warm from summer heat, and the tomatoes grow through the mild fall and early winter. They produce fruit from October through December or even January in frost-free areas. This works because Southern California's first frost usually does not arrive until November or December—much later than in other regions.

The catch is choosing the right variety. Determinate tomatoes (bush types that mature all at once) finish producing in 60 to 75 days, so they work well for fall planting. Indeterminate tomatoes (vining types that produce all season) need 80 to 100 days or more to reach full production, and an early frost can cut them down before they finish. If you love a particular indeterminate variety, you can still plant it in late July, but you will get less total fruit than a determinate type would give you.

Plant fall tomatoes by mid-August at the latest in most of Southern California. If you live in a frost-free zone or very close to the coast where frost rarely arrives before January, you can push the date to late August. Check your local first frost date—your county extension office or a local nursery can tell you when frost typically arrives in your area.

How to check soil temperature before planting

Do not rely on air temperature alone. A soil thermometer costs $5 to $15 and takes the guesswork out of planting. Push it 4 inches into the soil in the spot where you plan to plant, wait 2 minutes, and read the temperature. Do this in the morning before the sun has warmed the surface, because morning readings are more accurate than afternoon ones.

Tomatoes germinate slowly below 60°F and do not germinate at all below 50°F. They grow much faster once soil hits 70°F. If your soil is at 65°F, you can plant, but growth will be slow for the first few weeks. If it is at 70°F or warmer, plant right away—your tomatoes will establish quickly and start producing sooner.

Coastal versus inland timing differences

If you live within five miles of the ocean, your soil stays 10 to 15 degrees cooler than inland areas because the ocean moderates temperature. This means your spring planting window opens two to three weeks later than it does for inland gardeners. Where an inland San Diego gardener might plant in mid-March, a coastal San Diego gardener should wait until early April.

The same rule applies in fall. Coastal areas stay warmer longer, so your first frost arrives later—sometimes not until January. This gives you a longer fall growing season. You can plant fall tomatoes in late August or even early September if you live right on the coast, whereas inland gardeners should finish planting by mid-August.

If you are unsure whether you are in a coastal or inland microclimate, check your soil temperature. That is always the most reliable guide, regardless of where you live.

Transplants versus seeds: which to plant and when

Most Southern California gardeners buy transplants (seedlings) from a nursery rather than starting seeds indoors. Transplants are ready to plant as soon as soil reaches 60°F, and they start producing fruit weeks faster than seeds do. If you buy transplants in late February or early March for spring planting, choose ones that are 6 to 8 inches tall with thick stems and dark green leaves. Avoid leggy, pale seedlings that have been sitting in a cold greenhouse.

If you want to start seeds indoors, sow them 6 to 8 weeks before your planned planting date. For spring planting in mid-March, sow seeds indoors in late December or early January. For fall planting in late July, sow seeds in late May or early June. Keep seedlings under grow lights or in a bright window, and harden them off (gradually expose them to outdoor conditions) for 7 to 10 days before planting outside.

Common mistakes to avoid when timing your planting

The biggest mistake is planting too early because the air feels warm. A 70°F day in February does not mean the soil is 70°F. Soil warms much more slowly than air, especially after a cold winter. Plant too early and your transplants sit in cold soil for weeks, stunting their growth and wasting time. Use a soil thermometer and wait for the soil to warm, not the air.

The second mistake is planting fall tomatoes too late. If you wait until September to plant, your tomatoes may not have enough time to produce a decent crop before frost arrives. In most of Southern California, mid-August is the cutoff for fall planting. Coastal gardeners can push to late August, but do not wait longer.

A third mistake is choosing the wrong variety for fall planting. Indeterminate tomatoes need a long season to reach full production. If you plant them in August, they may still be ramping up production when frost arrives. Stick with determinate varieties for fall, or accept that you will get a smaller harvest from your favorite indeterminate type.

Frequently Asked Questions

Can I plant tomatoes in January in Southern California?

Not reliably. Soil is usually too cold in January, and frost risk is still high in most areas. Wait until late February at the earliest in inland areas, or early April if you live near the coast. The extra few weeks of waiting pay off in faster growth and better survival rates.

What is the first frost date for my area?

First frost dates vary by neighborhood in Southern California. Contact your county extension office, ask at a local nursery, or search online for "first frost date [your city]." Coastal areas often stay frost-free all winter, while inland valleys may see frost in November or December. Knowing your date helps you time fall planting correctly.

Do I need to harden off transplants before planting?

Yes, even if you buy them from a nursery. Spend 7 to 10 days gradually exposing transplants to outdoor sun and wind before planting. Start with 2 to 3 hours of morning sun on day one, add an hour each day, and move them to a sheltered spot at night. This toughens them up and prevents sunburn and wilting after planting.

Can I plant tomatoes in June or September?

June is too late for spring planting—soil is already hot and you will miss the mild spring weather. September is too late for fall planting in most of Southern California because frost will arrive before your tomatoes finish producing. Stick to the spring window (late February to early April) and fall window (late July to mid-August).

What if my soil is still cold in March?

Wait another week or two and check again. If you are in an inland area and soil is still below 65°F in late March, your garden may be in a frost pocket or shaded spot that stays cool. Consider planting in a sunnier location, or use black plastic mulch to warm the soil faster. Coastal gardeners should expect to wait until April.