Growing Tomatoes in Northern California

Grow a mix of tomatoes instead of betting the whole season on one variety.

Cherry tomatoes are usually the most reliable in high heat. Slicer tomatoes give the classic summer harvest but may stop setting fruit during heat waves. Paste tomatoes are best for sauce and canning because they have less juice.

Indeterminate tomatoes keep growing and producing until frost if they stay healthy. Determinate tomatoes make a shorter, heavier crop and are easier to manage in cages. For a family garden, plant both if you have room.

A good tomato transplant is short, sturdy, dark green, and not root-bound. Avoid tall, pale plants that already have flowers in a tiny pot.

If you start seeds indoors, use bright lights and do not start too early. Big root-bound tomato plants do not always beat smaller healthy plants once they go into the garden.

Before planting outside, harden plants off for 7 to 14 days. Move them into outdoor light slowly so they do not get sunburned.

Tomatoes hate cold soil. A warm week in March does not mean the soil is ready. Wait until nights are mostly above 50 degrees and the soil is near 60 degrees or warmer.

Plant tomatoes deep. Remove the lower leaves and bury part of the stem. Roots can form along buried tomato stems, which helps the plant handle heat later.

Space most tomatoes 24 to 36 inches apart. In hot areas, crowded plants get poor air flow and are harder to water evenly.

Do not wait until the plant falls over. Put cages, stakes, or trellis panels in the same day you plant.

A basic tomato cage is fine for determinate types. Large indeterminate tomatoes need stronger support. Cattle panel, T-posts, or a Florida weave can work well.

Tie stems loosely. The goal is support, not a tourniquet. Check ties every week as stems grow.

Tomatoes need steady moisture. Big swings from dry to soaked can lead to cracked fruit and blossom end rot.

Drip irrigation is best. Water at the soil, not over the leaves. In hot inland valleys, tomatoes often need deep watering 2 to 4 times per week by summer, depending on soil and mulch.

Add 2 to 4 inches of mulch after the soil warms. Mulch keeps roots cooler and slows evaporation. It also keeps soil from splashing onto leaves, which can reduce disease pressure.

You do not need to strip a tomato plant bare. Remove leaves that touch the soil, broken stems, and crowded growth inside the plant.

For indeterminate tomatoes, removing some suckers can make the plant easier to tie and harvest. For determinate tomatoes, prune lightly. Heavy pruning can reduce the crop.

In our heat, leaves protect fruit from sunscald. A tomato plant should breathe, but it still needs shade from its own leaves.

When daytime temperatures stay above 95 degrees and nights stay warm, tomato pollen can fail. The plant may flower but not set fruit. That is not always your fault.

Keep plants alive and healthy through the heat. Fruit set often improves again when temperatures ease. Use 30 percent shade cloth during extreme heat over 105 degrees, especially on young plants and exposed fruit.

Use the zone lookup at /learn/know-your-growing-zone and build a planting plan at /garden-planner so your tomatoes go into the ground before the worst heat arrives.