By Sommer Cartier, for Let’s Talk Plants! November 2024.
Savoring Summer's Best—Growing Tomatoes all Winter
After spending the summer months biting into home grown vine ripened juicy tomatoes, the thought of turning to flavorless store-bought tomatoes is almost unbearable. Fortunately, here in San Diego, we have the unique advantage of being able to grow tomatoes year-round, including during the winter months. With our mild climate and warm winters, you can enjoy fresh homegrown tomatoes even when most other regions are dealing with frost. However, winter tomato growing in San Diego comes with its own set of challenges and nuances. Below are some tips specifically tailored for growing tomatoes during the cooler months in our region.
Choosing the Right Varieties for Winter
Although San Diego’s climate allows for year-round gardening, the cooler and shorter days of winter require selecting tomato varieties that thrive in these conditions. Opt for early-maturing, cold-tolerant varieties like ‘Oregon Spring,’ ‘Siberian,’ ‘Glacier’, and ‘Stupice”, which tend to do well in lower light and cooler temperatures. Determinate varieties are also a good option since they grow more compact and mature faster, making them ideal for a winter harvest. Lucky for us, most of our local nurseries carry these varieties during the cooler months.
Managing Light and Temperature
Even though San Diego winters are relatively mild, daylight hours are shorter, and temperatures can dip at night, particularly in inland areas. While daytime highs might be in the 60s or 70s, nighttime temperatures can drop into the 40s or 50s, which can slow tomato growth. Consider placing your tomatoes in a sunny spot that gets at least 6-8 hours of sunlight. South-facing walls or patios that retain heat are great options. You can also opt to grow your tomato plants in containers that can be moved indoors when temperatures dip to lower 40s. For more consistent warmth, you can also use row covers or small greenhouses to trap heat and protect your plants from cooler temperatures.
Soil and Fertilizer for Winter Growth
Phosphorous remains an essential nutrient for strong roots and fruit production during the winter but be cautious about overusing nitrogen-rich fertilizers in cooler weather. High nitrogen can lead to lush foliage but fewer flowers and fruits, especially when the plant is already growing more slowly due to shorter days. Focus on using a low-nitrogen fertilizer with a higher content of phosphorus to support your tomato plants' root systems and ensure that you still get good fruit production even in the cooler months.
Winter Planting Tips: Loosen Roots, Plant Deep
These same transplanting techniques used in summer also apply in winter. When you plant your tomato transplants, be sure to loosen the root ball before planting and bury the stem deep to encourage the growth of adventitious roots. A more extensive root system will help the plant access nutrients and water more effectively, which is crucial in winter when growth can be slower.
Protect Against Winter Pests and Disease
Though winter in San Diego is mild, it’s still important to monitor for pests and disease. With cooler, damper conditions, fungal diseases like powdery mildew can be a problem, especially if airflow around the plant is restricted. Remove the lowest leaves and ensure good air circulation to prevent fungal growth. Additionally, monitor for pests like aphids, which can still be active during the winter months.
Encourage Pollinators to Assist
Even in winter, tomatoes still need some help with pollination. While there may be fewer natural pollinators like butterflies or bees (who become less active in cooler temperatures), you can encourage those that are present by planting pollinator-friendly flowers nearby, such as lavender, sage, sweet peas, rosemary, or African blue basil. If you notice fewer bees visiting your plants, you can also gently shake the plants to help distribute pollen and ensure fruit set.
Watering
Tomatoes need less water in winter than in summer, due to the lower temperatures and slower evaporation rates. Be careful not to overwater, which can lead to root rot. Water only when the top inch or two of soil is dry and try to water in the morning to avoid excess moisture sitting on the leaves overnight, which can lead to fungal issues.
With San Diego's mild winters, growing tomatoes in the cooler months is not only possible but can be incredibly rewarding. By choosing the right varieties, managing light and temperature, and applying proper care techniques, you can enjoy delicious, homegrown tomatoes year-round. Whether you’re growing in the ground or in containers, these tips will help ensure that your winter tomato crop is as successful as your summer harvest!
Editor’s note: This is not the first time, nor will it be the last, that Sommer and others have written about tomato gardening in our newsletter Let’s Talk Plants! To prove the point, here’s a non-exhaustive list of links to read more:
GROW WITH ABUNDANCE: Tomatoes 102 (sdhortnews.org)
FROM THE ARCHIVES: More From the Master Gardeners - Tomatoes 102.3 (sdhortnews.org)
GROW IN ABUNDANCE: Tips For Growing Heirloom Tomatoes (sdhortnews.org)
GROW WITH ABUNDANCE: Farewell to Blossom-End Rot (sdhortnews.org)
EDITOR'S LETTER: Tomatoes, Worthy of the Mania (sdhortnews.org)
COME INTO THE KITCHEN, GARDENER: Tomatoes, the Umami Superfood (sdhortnews.org)
FROM THE ARCHIVES: Tomato Fruits - Choose Your Size (sdhortnews.org)
BUGS AND BUGABOOS: Tomato Patch Postmortem (sdhortnews.org)
Article found in Let’s Talk Plants! January 2008, No. 160, page 8, SDHS_Jan_08.pdf (sdhort.org) titled Ethylene and the Flavor of Tomatoes by Carl Price and Ellen Reardon.
Article found in Let’s Talk Plants! April 2009, No. 175, page 7, SDHS_April_09.pdf (sdhort.org) titled Plants That Produce - Boy, Do I Love Tomatoes! By Richard Frost.
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