Plant tomatoes in California between mid-February and mid-March in the south, and mid-April to mid-May in the north, depending on your last frost date and soil temperature

California's long growing season means you can plant tomatoes earlier than most of the country, but the exact timing depends on where you live. The state spans multiple climate zones — coastal areas stay cool year-round, inland valleys heat up fast, and mountain regions frost late. Tomatoes need soil that has warmed to at least 60°F, ideally 65°F or higher, and they cannot survive a frost. Planting too early into cold soil causes the seeds to rot and seedlings to stall. Planting too late wastes the warm months you have.

Your last frost date is the key number. This is the average date of the final frost in your area. In Southern California (San Diego, Los Angeles, inland valleys), the last frost typically falls between mid-February and early March. In the Bay Area and Central Coast, it lands in mid-April. In the Sierra foothills and mountain regions, it can be as late as May or early June. You can find your exact date by searching "[your city] last frost date" or checking the USDA Plant Hardiness Zone map for your zip code.

Key Takeaways

  • Southern California can plant tomatoes in mid-February to mid-March, while Northern California and coastal areas should wait until mid-April to mid-May.
  • Soil temperature matters more than air temperature — wait until soil reaches 60°F to 65°F, which usually happens one to two weeks after the last frost date.
  • Starting seeds indoors six to eight weeks before your planting date gives you larger transplants that produce fruit faster than direct seeding.
  • Tomatoes planted too early in cold soil rot or sit dormant; tomatoes planted in June or later in inland areas may not ripen before heat stress sets in.

Southern California planting window: mid-February through March

If you live in San Diego, Los Angeles, Orange County, inland Riverside or San Bernardino counties, or the Central Valley, your last frost date falls between mid-February and early March. This means you can plant tomato transplants (not seeds) outdoors in mid-February and continue through March. Soil in these regions warms quickly once winter rain stops, usually by late February.

Planting in February gives your tomatoes a three-month head start before the intense heat of May and June arrives. Early-planted tomatoes set fruit in spring when temperatures are moderate, then produce through summer. If you wait until April or May in these regions, your plants will be flowering during the hottest weeks, which causes flower drop and reduces your harvest.

For Southern California, starting seeds indoors in late December or early January gives you transplants ready to move outside in mid-February. If you buy transplants from a nursery, look for stocky plants with dark green leaves, not tall leggy ones that have been sitting in a greenhouse too long.

Northern California and coastal planting window: mid-April through May

In the San Francisco Bay Area, Sacramento, the Central Coast (Monterey, Santa Cruz), and inland areas above 2,000 feet elevation, the last frost date falls between mid-April and mid-May. Soil in these regions stays cool longer because of coastal influence, higher elevation, or spring rain. Planting before mid-April often results in seeds rotting or transplants sitting stunted in cold soil for weeks.

Northern California's advantage is a longer, cooler growing season. Tomatoes planted in mid-April or early May will produce steadily through September and into October without the heat stress that affects Southern California plants. You can plant heat-sensitive varieties like San Marzano or Brandywine in the north and get excellent results; in the south, these same varieties often drop flowers in June heat.

Start seeds indoors in late February or early March for Northern California transplants. This timing gives you plants large enough to handle outdoor conditions by mid-April without them becoming root-bound in their containers.

Checking soil temperature before planting

Air temperature and soil temperature are not the same. A warm day in March does not mean the soil is warm enough. Tomatoes planted in soil below 60°F will sit dormant, rot, or grow so slowly that pests and disease catch up to them. The easiest way to check soil temperature is to buy a straightforward soil thermometer from a garden center or online — they cost five to ten dollars and take a reading in seconds.

Push the thermometer four inches into the soil in the morning, wait two minutes, and read the temperature. Do this on three or four days in a row. If the average is 60°F or higher, you can plant. If it is below 60°F, wait another week and test again. In most of California, soil reaches 60°F about one to two weeks after the last frost date, but this varies by year depending on how much rain fell and how sunny it has been.

If you are impatient and plant in cold soil anyway, cover the soil around each plant with black plastic or dark mulch for two weeks. This traps heat and warms the soil faster. Remove the plastic once the plant is growing actively.

Starting seeds indoors versus buying transplants

You have two paths: start seeds indoors six to eight weeks before your planting date, or buy transplants from a nursery. Starting seeds indoors costs less per plant and gives you more variety choices — nurseries usually stock only five to ten common types. Buying transplants is faster and requires no indoor space or grow lights.

If you start seeds indoors, use a seed-starting mix (not garden soil), keep it moist but not waterlogged, and provide 14 to 16 hours of light per day under a grow light or in a very sunny south-facing window. Seeds germinate in five to ten days at 70°F to 75°F. Once they sprout, lower the temperature to 65°F to 70°F and keep the light close to prevent leggy growth. Thin seedlings to one per cell once they have two true leaves.

If you buy transplants, choose plants that are six to eight inches tall with thick stems and dark green leaves. Avoid plants that are flowering already — they are stressed and will produce less overall fruit than plants that flower after being planted in the ground. Harden off transplants by setting them outside in shade for an hour or two, then gradually increasing sun exposure over a week, before planting them in the garden.

Adjusting for microclimates in your yard

Even within a single neighborhood, microclimates exist. A south-facing wall or a spot protected by a fence warms up weeks earlier than an open, north-facing bed. A low-lying area where cold air settles frosts later in spring than a slope. If you have a warm microclimate — a south-facing wall, dark mulch, or shelter from wind — you can plant one to two weeks earlier than the average last frost date for your area.

If your yard is in a cold pocket — a low spot, a north-facing bed, or an area exposed to wind — wait one to two weeks longer than the average date. Observe your yard over a season or two. Note where frost lingers longest in spring and where the soil warms fastest. Use that information to choose the best planting spots for tomatoes and other heat-loving plants.

Succession planting for a longer harvest

You do not have to plant all your tomatoes on the same day. Planting in waves — two weeks apart — spreads your harvest across more weeks and reduces the risk that a single heat wave or pest outbreak will wipe out your entire crop. In Southern California, plant the first batch in mid-February, a second batch in early March, and a third in mid-March. In Northern California, plant in mid-April, early May, and late May.

Early plantings produce fruit in late spring and early summer. Later plantings produce in mid-summer and fall. This strategy also lets you experiment: if the first planting does poorly, you can adjust spacing, variety, or care for the second batch. If the first planting thrives, you know what worked and can repeat it.

Frequently Asked Questions

Can I plant tomatoes in California in January?

In Southern California, you can plant transplants (not seeds) in late January or early February if soil temperature is already 60°F or higher, which sometimes happens after a warm winter. In Northern California, soil is rarely warm enough in January. Test your soil temperature before planting rather than guessing based on the calendar.

What happens if I plant tomatoes too early?

Seeds rot in cold soil. Transplants sit stunted and do not grow for weeks, wasting the warm season. Cold-stressed plants are also more vulnerable to root rot, damping off, and pest damage. It is better to wait two weeks and plant into warm soil than to plant early and lose the plant.

Is it too late to plant tomatoes in June in California?

In Northern California and coastal areas, June planting can work because the growing season extends into October. In Southern California inland valleys, June planting is risky — plants will flower during peak heat in July and August, causing flower drop and reduced fruit set. If you miss the spring window in the south, wait until late July or August to plant fall tomatoes.

Do I need to harden off seedlings before planting?

Yes. Seedlings grown indoors are tender and will wilt or die if moved directly into full sun and wind. Spend one week gradually exposing them to outdoor conditions — start with shade and a few hours outside, then increase sun and time each day. This toughens the plant and prevents transplant shock.

What if my area does not have a clear last frost date?

Coastal California and some microclimates rarely frost, so a traditional last frost date does not explore. Instead, use soil temperature as your guide — plant when soil reaches 60°F to 65°F. You can also ask neighbors or a local nursery when they plant tomatoes; they have years of local experience.