Tomatoes, When to Grow Depends on Microclimate
Advice to Grow By, The Press Democrat
Sonoma County Master Gardeners
Contributors to this column: Renee Hayes and Debbie Westrick
Jane T. asks: I want to grow lots of tomatoes this year. When can I start planting them and which ones are the best to grow in Sonoma?
Answer: It’s just about time to put tomatoes in our Sonoma County gardens. It may be confusing to know exactly when to plant tomatoes in our county due to the many different microclimates here. The northern cities of Healdsburg, Windsor and Santa Rosa, as well as western Sonoma, warm up much earlier than the cooler areas of Sebastopol, Rohnert Park, Cotati and Petaluma.
Here’s a simple rule of thumb: Wait until after April 15—on average, it’s the last day with frost—to plant tomatoes. Warm soil is key. Use a spot in your garden that gets six to eight hours of full sun. Then follow these steps to plant tomatoes for a delicious Caprese salad or salsa fresca this summer:
- Dig a hole deep enough to bury all but the top 3 inches of plant foliage.
Before planting, fill the hole with water and add compost. You also may add a well-balanced organic fertilizer, labeled “7-5-7.” Those numbers refer to the nitrogen, phosphorus and potassium content of the fertilizer. Directions on the package will tell you how much fertilizer to use per plant.
- Gently place the seedling in the hole, fill in with soil and press firmly around each plant to make a slight depression to hold water. Water the soil thoroughly to settle the soil and eliminate any air pockets around the roots.
- Pinch off any lower leaves that are near the soil and add support just after planting by staking, caging or trellising each plant. Plant parts that trail on the ground are more likely to get diseased and attract pests.
- Place determinate tomato plants 18 to 24 inches apart; plant indeterminate tomatoes 24 to 36 inches apart.
- Add 1 to 2 inches of mulch around the tomato plants to help retain soil moisture, keep the roots warm and reduce weed growth.
Tomatoes require regular watering. Keep the soil evenly moist and avoid spraying the leaves. For watering by hand, water once or twice a week. First, check for moisture with your finger. If the soil feels damp 2 to 3 inches deep, there is no need to water.
You may want to add beneficial plants, such as marigolds, basil, borage, chives and parsley. Not only do they attract pollinators to your garden—bee-pollinated tomatoes have higher levels of vitamin C—they also become tasty treats alongside your summertime tomato dishes.
When deciding which is the right tomato variety for your climate and your planting area, it helps to know the difference between determinate and indeterminate tomatoes.
Determinate tomatoes grow to approximately 3 to 5 feet, bear most of their fruit within four to six weeks and then decline. They are wonderful for large pots or grow bags. Determinate tomatoes are usually early ripening and used for canning. Some determinate tomato varieties that grow well in Sonoma County are Sophie’s Choice, Glacier and Roma.
Indeterminate tomato plants bear tomatoes throughout the summer, until the vine is cut down or killed by frost in the fall. Indeterminate tomato varieties that grow well in Sonoma County include Stupice, Early Girl, New Girl, Crimson Carmelo, HillBilly, Green Giant and Sungold cherry tomatoes.
To read more about planting tomatoes in containers, irrigation and pollination, check out How Tomatoes are Pollinated.