Why not check over on the Tomatoes Forum (linked at the top of this forum's front page) as this question is frequently discussed there?

It is your choice of course, but topping tomato plants is certainly NOT a common practice. The biggest drawback of course is lost production.

Dave

Here is a link that might be useful: Growing Tomatoes Forum

I pinch off the growing tips and immature bud trusses of my tomato plants starting two months before estimated date of first frost. It takes about 60 days for a large beefsteak to go from flower to ripe fruit, and this way I have very few green tomatoes when the frost hits, and most of those are large enough to ripen in storage. The immature growth will grow about a foot by the time it is mature, which puts it well over top of my cages, but the tomatoes are only at the top of the cages so are supported when the top growth bends over. I have to asume that topping this way provides more nutrients for the fruit since the plant is not producing as much new growth, but if you have fungal problems and the bottom leaves are dieing during this time topping would be a bad thing. simply pinching off the immature bud trusses, and not the growth tips would be better.

Thanks! I appreciate the responses. I wasn't sure how common of a practice it was but I have heard and read more about it recently.

"but topping tomato plants is certainly NOT a common practice. The biggest drawback of course is lost production"

But if pinched off at the top due to unwieldly height (over 7'), won't the bottom branches begin to produce blossoms and fruit in lieu of the top trusses which 'would have been?'?> If the rate of mine continues, my tomatoes are going to be 15 feet tall. For my circumstances (backyard gardener who moved into the front yard due to sun issues) I am trying to be considerate of the appearance of my maters. These guys are getting so HUGE and the fruit is at the top. I would love to force some more bottom blossoming. Thanks for advice.

As I said above, this is discussed in great deal over on the Growing Tomatoes forum but the basic info lies in understanding how a tomato plant grows.

Indeterminate varieties of tomatoes are vines. They grow like any vine does. That means that given adequate nutrients, water, no injury, and sun many varieties can easily reach 12-18 feet long. That doesn't mean the entire height has to be supported - they drape and continue growing quite well.

But they produce just like any vine does too - new growth progresses up the plant, not back at the base. As the plant ages and grows lateral branches, moving up the plant, are sealed off from the main stem. New production happens on the new growth, not back on the older part of the plant. Top it and that production is lost. End of the season topping - fine. Early season (like now for most) topping isn't a common practice by any means.

If plant appearance or plant size is more important to you than production of fruit then top it if you wish but recognize what you will lose. And understand that topping doesn't stop it for long from growing on. It will sprout 2 new vining branches from the branch junction just below the cut (not way back down the plant). They will be thinner and weaker and the fruit if any will be smaller, but it will try to keep going. That is its nature.

Better yet if plant size and appearance is the primary consideration for you then grow determinate or short node (ISI) indeterminate hybrids that all naturally remain in the 4-6 foot range.

Dave