Tomatoes thrive in consistent warmth, and the Los Angeles climate offers an extended growing period compared to most of the United States. This mild environment allows for a long, productive summer season and the possibility of a second harvest in the fall. Successfully growing tomatoes in Southern California depends less on a single calendar date and more on understanding two primary factors: the temperature of the soil and the specific microclimate of the planting location. Timing the planting correctly ensures the young plants establish themselves before the extreme heat of mid-summer causes flowers to drop.
Defining the Optimal Planting Windows
The most accurate indicator for transplanting tomatoes outdoors is the soil temperature, which must consistently be at least 60 degrees Fahrenheit for healthy root development. Planting into colder soil causes the seedlings to sulk, leading to stunted growth because the roots struggle to absorb nutrients efficiently. Ideally, the soil temperature should hover between 65 and 70 degrees Fahrenheit to promote rapid establishment and growth.
For the main summer harvest, the primary window for setting out purchased tomato transplants in the Los Angeles area begins after mid-March. While the risk of a killing frost is low, this period reliably marks the time when the soil has warmed sufficiently for the heat-loving plants to thrive. Planting at this time allows the plants to mature and set fruit before the most intense heat arrives in July and August.
A significant advantage of the Southern California climate is the opportunity for a secondary, fall tomato crop. To achieve a harvest that extends into late fall, new transplants should be set out in late July or early August, with no planting later than the first half of September. This second round provides young, vigorous plants that utilize the warm soil and mild autumn days to ripen fruit before cooler temperatures slow production.
How LA Microclimates Influence Timing
Los Angeles is not a uniform growing environment, and its distinct microclimates significantly influence the ideal planting schedule. The most notable difference exists between coastal areas and the inland valleys. The coastal zones, often within a few miles of the Pacific Ocean, experience the cooling effects of the marine layer, commonly known as the “June Gloom.”
This consistent cloud cover and cooler air near the coast can delay soil warming, pushing the ideal transplant date later, sometimes into late April or even May for gardeners near the beach. While the mild temperatures extend the overall growing season, the slower start means that large-fruited varieties may need to be planted later to ensure they ripen during the warmest part of the summer. Coastal tomatoes often have a longer productive life than those inland due to the steady, moderate temperatures.
Conversely, gardens in the inland valleys and eastern parts of the county experience hotter, drier conditions and less marine influence. The soil warms earlier in these areas, allowing for a safe transplanting period closer to the start of March. However, these plants must contend with summer daytime temperatures that frequently exceed 90 degrees Fahrenheit, which can cause flowers to drop and production to temporarily cease.
Adjusting the Timeline: Seeds vs. Transplants
The decision to start tomatoes from seed or purchase nursery transplants directly impacts the required planting timeline. Buying a transplant from a nursery means the planting timeline begins immediately, aligning with the mid-March to mid-April window for setting plants outdoors. This is the simplest approach for gardeners who want to skip the initial propagation phase.
Starting tomatoes from seed requires a significant lead time to ensure the seedlings are robust enough for the garden. Seeds should be sown indoors approximately six to eight weeks before the planned outdoor transplant date. For Southern California, this means indoor sowing should begin in January or early February to prepare plants for the outdoor spring window.
Before moving any seedlings into the garden, they must undergo a gradual process called “hardening off.” This involves slowly acclimating the young plants to outdoor conditions, including direct sunlight, wind, and cooler temperatures, over a period of seven to ten days. Skipping this step can shock the tender plants, leading to severe setbacks once they are permanently placed outdoors.
Selecting Varieties for the Long LA Growing Season
The lengthy growing season in Los Angeles makes the selection of the right tomato variety a factor in success. Gardeners should prioritize indeterminate varieties, which continue to grow, flower, and set fruit throughout the entire season until cold weather arrives. This growth habit is well-suited for the long potential growing period in Southern California.
It is important to choose varieties that are specifically known as “heat-set” or heat-tolerant, especially for inland gardens. Standard tomato varieties often fail to set fruit when nighttime temperatures remain above 72 degrees Fahrenheit. Heat-tolerant cultivars have the genetic capacity to overcome this heat-induced sterility and continue production during the hottest summer months.
Recommended Heat-Tolerant Varieties
Heat-tolerant cultivars include ‘Celebrity,’ ‘Heatmaster,’ ‘Solar Fire,’ or ‘San Marzano.’ Even heirloom varieties like ‘Cherokee Purple’ and ‘Pruden’s Purple’ are noted for their ability to withstand higher temperatures. Selecting these resilient types ensures a continuous, high-quality harvest, rather than a gap in production when the summer heat spikes.