Training Hybrid Tomatoes
When growing hybrid tomatoes; i.e., any tomato other than an heirloom variety that grows upright, I have found that it is best to train the plant to one main stalk. To accomplish this, you must go against all natural instinct and pinch off the extraneous shoots that sprout between a 'v' junction on the plant. These shoots are commonly referred to as "suckers."
There are two extraneous suckers that should be pinched off in this photo. The shoot growing out of the 'v' in the lower left and the shoot growing between the 'v' in the upper right should both be pinched off since they are growing between the main stalk and an adjoining stem. Leaving these shoots will cause a second and third "main stalk" to form.
Training tomatoes to one main stem is particularly necessary when using stakes to support the plants. This method allows you to easily tie the plant up as it grows and ensures the stake can support the full weight of the mature plant. If you allow these suckers to grow, the weight of the additional shoots will cause the branches to snap off at the base, and if there is more than one main stalk, it will be difficult to know which stalk to tie up - you will end up having to tie up each of the stalks separately.
Another reason to remove suckers is to promote fruit growth. You want your plants to put their energy into producing fruit, not producing more green shoots. If you leave the suckers on the plant, you will have smaller fruit and possibly less of it. I admit that there are many schools of thought in this area, but this is the method I have used for the past two years and experienced what I consider great success.
Heirloom tomatoes grow like haphazard maniacs, so it is best to just cage these varieties and let them grow however they choose. We waited too long to cage our heirlooms, and now we are having to tie up their branches to keep them from snapping. We tried to cage them last week, and oh my, what a fiasco that was. Lesson learned for next year! This is our first year growing heirlooms, so I won't be too hard on myself when the branches snap from the weight of the fruit!