UC Master Gardeners of San Mateo & San Francisco Counties

Growing Container Tomatoes in San Francisco

San Francisco is a city of microclimates (cool, foggy, windy, wet and sunny), due to its location by the ocean and bay. However, you can successfully grow tomatoes. This page provides guidelines for growing tomatoes in containers.

Tomato Fundamentals

  • There are two categories of tomatoes: determinate and indeterminate. Determinate varieties are ideal for containers, growing to limited sizes with somewhat lower yield. Indeterminate tomatoes offer more varieties and higher production but need more maintenance and pruning.
  • There are several tomato varieties: cherry, grape tomatoes, standard/classic, and beefsteak.
  • Areas with less than 6 hours of full sun every day, choose cherry tomatoes such as: Sun Gold, Black Cherry, Juliet Hybrid.
  • Consider a determinate variety for less pruning and maintenance: Bush, Early Girl, Rutgers.
  • Other coastal friendly cultivars to consider include: Carmello, Washington Cherry, San Francisco Sunrise.

Soil and Fertilization

  • Tomatoes thrive in slightly acidic soil. Select a potting soil with a pH between 6.5 and 7.0.
  • Before planting, amend soil with compost and organic matter like earthworm castings.
  • Use a fertilizer lower in nitrogen (N), higher in phosphorus (P) and potassium (K), such as N-P-K 8-32-16, 6-24-24, 10-20-20.
  • Add calcium and magnesium supplements (like oyster shell) and trace minerals such as Azomite to amend the soil.
  • Re-apply compost or liquid organic fertilizer to topsoil every 4 weeks.

Container Planting

  • Plant tomatoes after night temperatures consistently stay above 50° F (typically April or early May) to prevent disease.
  • Choose a location with at least 6 hours of direct sunlight daily (8 + hours a day for larger varieties).
  • Use a container holding 15-20+ gallons that’s at least 24” deep with drainage holes.
    • Fill half the pot with soil, then gently remove the seedling from its original pot, lightly massage the soil to loosen the roots if necessary.
    • Plant deep so all lower leaves are 2-3” from the soil level. For leggy plants, remove lower leaves allowing 5-6 inches of the plant exposed above soil.
    • Fill the hole with soil, pressing down lightly.
  • Place a catch basin or saucer under the container as a reservoir for excess water.
  • As the tomato plant grows upward, fill in more soil.
  • When the soil is within 2-3” of the container rim apply 1-2” of mulch. The mulch provides a barrier between the leaves and soil, maintaining moisture and reducing disease transmission.

Watering

  • Tomatoes need consistent moisture. An inconsistent water supply can cause cracking and blossom end rot.
  • Tomatoes in pots can dry out quickly so check them frequently. If the top inch of soil feels dry, it’s time to water.
  • Encourage healthy roots by watering deeply.
  • Water slowly at the base of the plant and avoid splashing or watering from above which invites disease.

Support

  • Use stakes or cages to keep plants off the ground. Position stakes outside the root ball.
  • As they grow, tie plants loosely using soft twine or plant ties in a figure-eight formation.
  • For indeterminate varieties, 6-8’ stakes may be required.
  • Central staking effectively maintains the central stem.

Pruning and Maintenance

  • Suckers are small shoots that develop between a stem and a leaf. Do not prune suckers on determinate plants. Prune all suckers from indeterminate varieties, except as follows:
    • Keep the first sucker beneath the first flower cluster as a limb. Prune all suckers below it.
    • Keep 2-3 suckers above the first flower cluster for additional limbs.
  • Prune crowded foliage to keep air circulating through the plant, which reduces humidity and prevents fungal diseases in our cool San Francisco climate.
  • Remove lower leaves that touch the soil to prevent exposure to soil-borne pathogens.

Harvesting

  • Tomatoes typically mature 60-80 days after transplanting, depending on the variety.
  • Harvest tomatoes when fully colored and slightly soft to the touch.
  • You can also pick slightly underripe tomatoes with the vine attached to ripen later.
  • Regular harvesting encourages the plant to produce more fruits.

Additional Information