For a cold climate we find that to prune indeterminate tomato plants helps us to harvest ripe tomatoes earlier in the summer. Only indeterminate, not dwarf tomato varieties, can be pruned. One very important thing to keep in mind though, is the variety of tomato you're growing – this will determine whether or not you should prune your tomato plants. When to remove tomato suckers. Pruning tomato plants is actually an optional technique. Pruning will give you earlier and better fruit. If allowed to grow, suckers eventually produce flowers and fruits, but the plant will be very dense with growth. A sucker is a shoot that forms in the joint where a leaf meets the stem. Some gardeners swear by it, while others choose not to do it. Cutting away too much of the plant can cause shock. If a tomato plant becomes overgrown, prune away no more than one-third of the plant. How to prune indeterminate tomato plants. Tomato suckers are produced on both determinate and indeterminate tomato plants. By pruning the plant to a single stem you can grow more plants in a small space. You should only prune indeterminate varieties. Pruning tomato suckers is about controlling and managing the growth of the plant.