By Brenda Troutman
Tomatoes are the number one fruit (technically speaking) grown by home gardeners and the most popular vegetable in the world. Climate change has led to more weather extremes in cold, heat (especially), drought and rain creating challenges to growing specialty crops. Environmental stressors reduce the quality of plants and their ability to set fruit. When deciding which tomato plants to grow there is an abundance of choices. Some tomato varieties are better suited for temperature extremes then others.
Tomato plants are warm blooded and should not be planted outside until the soil temperature is above 60 degrees during the day (50 degrees night) and all danger of frost has past. Springs unpredictability and fluctuating temperatures can frustrate an over zealous gardener like myself who started tomato seeds indoors in January. These bush (determinate) or vine (indeterminate) plants do best when temperatures are between 65-85 degrees and the plants receive six or more hours of full sun daily. When temperatures drop below 65 degrees the plants will suffer, stunting plant growth and delaying fruiting. “Blossom drop” occurs when the days are warm but the nights dip below 55 degrees. The flowers fall off before being pollinated, and no fruit is set.
Pollination usually occurs between the hours of 10 AM to 2 PM. When summer temperatures reach 90 degrees during the day and do not drop much below 76 degrees at night (add in high humidity) pollen granules burst, preventing pollination. The plants go into survival mode, losing their flowers to conserve moisture.
Providing shade during the hottest part of the day, mulching to keep soil cool and moist and extra watering will help tomatoes beat the summer heat. Determinate varieties that have shorter “days to maturity” or “days to harvest” will have mature fruit before the summer heat kicks in. Once the flowers are pollinated and the fruit is set, the bulk of the tomatoes will ripen within two weeks after which the plants will start to die back.
Luckily, there are tomato varieties (hybrid and heirloom) referred to as “cold set” or “heat set” that can tolerate temperature extremes.
A partial list of varieties that will set fruit at or below 55 degrees (cold set) includes, Early Girl, Celebrity, Gold Nugget, Bush Beefsteak, New Yorker and Glacier. Many of these varieties also mature in a shorter amount of time 52-70 days making them a good choice for a late season fall planting. When temperatures do threaten to fall below 55 degrees, covering the plants with clear plastic can warm things up by as much as 20 degrees.
Just like there are cold tolerant varieties, there are tomato plants that can take the heat. Examples of hybrids are Bella Rosa, Big Beef, Florida, 4 of July, Heatwave, Homestead, and Sweet 100. Some heirloom varieties are Green Zebra, Sioux, Quarter Century and Arkansas Traveler. But even these varieties have their limits. When temps reach mid 90’s during the day and do not fall much below 80 degrees at night, production is hampered.
Choosing tomato varieties that best match your growing conditions can maximize the yield from your garden.