When to Plant Vegetables in Sonoma County

Timing is So Important!

By Joe Michalek, Sonoma County Master Gardener

Every spring the nurseries stock their benches with an assortment of frost tender vegetable plants just waiting for the customers who want to get an early start in their garden. Little do those gardeners remember that just last year their local nursery did the same thing and the plants that they purchased languished in the cold, soggy soil, waiting to grow until the soil warmed up.

Tender, heat-loving veggies such as tomatoes, squashes, beans, peppers, and basil, to name a few, all require both warm soil and an air temperature of at least 65° to thrive. The gardener can enhance the nighttime temperature by using cloches to cover plants but this can be expensive and time consuming. They need to be taken off during the day, as the hot air inside the cloche will bake the plant.

In our area the last killing spring frost is generally around the 15th of April. This means that the soil is just getting warm by the 1st of May. Just to be on the safe side it is advisable to hold off planting tender summer vegetables until the middle of May, as they all do best when the soil temperature is at least 55°. Below that temperature there is virtually no growth. The plants that are placed in the ground when the temperature reaches the threshold for growth will produce fruit at the same time as the plant placed into the ground earlier. If you are anxious to get the plants into the ground and do not know the exact temperature of the soil, invest in a soil thermometer so that there is no question about the soil temperature in your garden. Keep records of just how well your plants do each year, and when they were planted, so that you can determine the best time to plant in your area as there are many microclimates in Sonoma County.

So hold off on the summer veggies for a couple of months, and take advantage of the cool period now to plant lettuce and other leafy greens and enjoy some great salads while you ponder which varieties of tomatoes to plant in May!