The true definition of the word determinate is; having defined limits, or; conclusively determined.
All determinate tomatoes are varieties that have been bred to grow shorter in height than indeterminate types. Determinate varieties may only grow to be about four or five feet tall. They will stop growing when flowers have set their fruit on the terminal bud. Determinate tomatoes will ripen their entire crop at the same time and then they will complete their lifecycle and die back.
Supporting your tomatoes is always important, and it doesn’t matter whether they are determinate or indeterminate. They all need some sort of support. No pruning is necessary with either type of tomato; however, if you do pinch out the sucker growth of a determinate tomato, you are removing a lot of the potential for flowers to set fruit. I grow Celebrity and Roma varieties. These two examples are known as determinate tomatoes. Remember: Do Not Pinch Suckers!
Indeterminate varieties or the so called “vining” tomatoes require a lot of support. Using 6” square wire mesh used in the pouring of concrete driveways is a good material to wrap in a three foot diameter circle for a cage. These cages could be as tall as eight feet, depending on the width of the wire mesh. This type of wire mesh can be found at your local “big box” hardware store, or lumberyard.
Indeterminate tomatoes grow throughout the season putting on a lot of vegetation and fruit until it gets so cold that the plants can be killed. They are known to flower, bear fruit and ripen all at the same time as the growing season progresses. Remember: it is not necessary to pinch out the suckers on an indeterminate variety of tomato, but you may have been taught, or are already practicing this acceptable method of improving fruit quality. I’ve planted Early Girl, and cherry tomatoes that are indeterminate varieties.
Regardless of the variety or its determinate or indeterminate nature, during times of high heat and humidity, you are bound to see fruit set decrease dramatically. The pollen gets too sticky, and is unable to float to other flowers. Bees are not typically found out working in the extreme heat of the day in places like Texas.
Always check the label in the pot or the back side of a seed packet prior to purchasing your tomatoes so that you know if they are determinate or indeterminate. You will better understand your tomatoes growth patterns and how to best care for them during the growing season.