Yard and Garden: Tomatoes

Tomatoes, the most popular vegetable in the home garden, come in a variety of sizes, shapes, and colors — including red, yellow, orange and pink. Home gardeners can select from bite-sized cherry tomatoes to giant beefsteak varieties. ISU Extension horticulturists share details about tomato varieties that growers can use in making tomato selections. To have additional plant and garden questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

In regards to tomatoes, what is meant by the terms determinate and indeterminate? 

Determinate and indeterminate refer to the tomato variety’s growth habit.

Determinate tomatoes are small, compact plants. They grow to a certain height, stop, then flower and set all their fruit within a short period of time. The harvest period for determinate tomatoes is generally short, making them good choices for canning.

Indeterminate tomatoes continue to grow, flower and set fruit until killed by the first frost in fall. Accordingly, the harvest from indeterminate varieties often extends over a two or three month period. Yields are generally heavier than determinate types, but are usually later to mature. Indeterminate tomatoes are large, sprawling plants which perform best when grown in wire cages or trained on stakes. 

In catalogs, tomato varieties often have several letters, such as VFNT, after their name. What do the letters stand for? 

The letters indicate the tomato variety’s resistance to nematodes and several diseases. The letter “F” following the varietal name indicates resistance to one or more races of the Fusarium wilt fungus. The letters “V”, “T” and “N” indicate resistance to Verticillium wilt, tobacco mosaic virus and nematodes, respectively. Resistance to tomato spotted wilt virus is designated as “TSWV.”

Resistance to a disease does not mean the plant is immune to the disease. Resistant varieties are less likely to become infected with the disease when compared to susceptible varieties. When plants become infected with a disease, the severity of the disease on a resistant plant will be far less than a susceptible plant.

Most open-pollinated, heirloom tomato varieties have little resistance to common tomato diseases. Most hybrid tomato varieties have resistance to one or more diseases. 

Are yellow tomatoes less acidic than red tomatoes? 

The acidity levels of yellow tomatoes are similar to red tomatoes. Yellow tomatoes contain more sugar than red tomatoes. As a result, yellow tomatoes taste sweeter than red tomatoes.