Growing Fall Tomatoes, A Niche Opportunity for Market?

by Keith Baldwin, Farm Services Coordinator

Summer heat, humidity, and insect and disease pressure normally limit the production of spring-planted tomatoes to the months of June, July, and August. Multiple or sequential spring plantings are only somewhat effective in extending harvest beyond this “market window” because of the fruiting characteristics of tomatoes. Most tomato cultivars stop setting fruit when daytime and nighttime temperatures are above 90°F and 70°F, respectively. However, there are tomato cultivars available today that are “heat tolerant.” These cultivars will continue to set fruit in spite of temperatures above the thresholds described above. And they will provide you with tomatoes when no one else has any growing.

A critical requirement for planting tomatoes in mid-July for fall harvest is having “heat tolerant” tomato seedlings ready for planting at that time. Unfortunately, most commercial vendors will not have any transplants for sale at planting time in July, let alone heat-tolerant cultivars. For a mid-July planting, this means you must purchase and sow seed by mid-June or earlier. It is key, at this busy time of year, when starting seed can be the last thing on a grower’s mind, to sow the seed on time.

Though fall tomatoes can be produced on bare ground, growing the crop on beds covered with white plastic or straw mulch provides many benefits. White plastic mulch reflects sunlight, which reduces the soil temperature underneath the plastic and the air temperature above it. Straw mulch shades the soil surface, providing a cooler, moister root zone. Plastic-covered beds also contribute to the drying of plant leaves after rainfall or irrigation. Many diseases require wet leaf surfaces for infection to occur.

Fall tomatoes planted on plastic mulch must be irrigated. Plant establishment and survival require a moist root zone, and both the frequency and dependability of rainfall are low in July. The soil under the plastic should be thoroughly wetted by irrigation prior to transplanting. Stressed plants are non-productive plants, so consistent moisture is important for vigorous growth. When tomatoes are fully grown, each plant will require approximately 0.65 gallons of water per day. Drip irrigation systems are designed to provide consistent and uniform moisture in the root zone by providing irrigation water on a daily basis. Most common drip tubing distributes approximately 0.5 gallons per minute per 100-row feet of tubing. Running the system daily for about 80 minutes will supply the right amount of water.

While most heat-tolerant cultivars lack the outstanding quality of the “standards” produced for market, some of the better-tasting cultivars listed below are worth trying.

 Have questions about season extension? Get in touch!