Q: If I plant indeterminate tomatoes can I crop the top to keep them from growing tall?
A: Pruning an indeterminate tomato to make it bushier is possible but you’ll be fighting Mother Nature.
After planting, indeterminate tomatoes grow for a while and then produce a flower cluster. The leaf below the flower cluster then sends up a shoot (sucker) which produces three leaves and ends once more in a flower cluster. And once again the leaf below the flower cluster sends up a shoot, produces three leaves and a flower cluster on the end. This sequence repeats endlessly and gives the appearance of a long tomato vine.
Determinate tomatoes send up several shoots from below the first flower cluster. Each one makes a couple of leaves and ends with a flower cluster. This repeats only a few more times. Since there are more shoots under each flower cluster and fewer leaves between clusters, the plant takes on a bushy appearance.
So theoretically you could remove the growing tip of an indeterminate tomato vine to make it produce more shoots and then remove the tips of those shoots to give the plant several growing tips near the base. You would have a semi-bushy plant, but it would sprawl outward because after a couple of tip removals you would need to let the vine grow and flower as nature intended.
If you want a bushy plant, you would be better off to grow a determinate variety like ‘Celebrity’, ‘Roma’ or any variety labeled “patio” or “bush” type.