I hear these questions every year: Should I prune my tomatoes? When? How do I do it?
First things first, only indeterminate-type tomatoes should be pruned. Because indeterminate plants continue to grow and produce tomatoes throughout the season, you can prune their side shoots (also known as "suckers"), whereas if you pruned determinate tomatoes that produce only once a season, you would be reducing the overall yield.
Pruning indeterminate tomatoes can increase fruit size, help tomatoes ripen faster, and help reduce disease. It will not increase the number of tomatoes you get, but you will probably get more "perfectly" shaped and sized tomatoes. Even though I love even the small or ugly tomatoes, I prune some of my tomato plants for the sheer beauty of a big, hearty tomato.
There are 3 different strategies for pruning suckers off tomatoes:
Prune only those suckers below the first flower/fruit cluster.
Wait until suckers have four leaves and prune off the top two, leaving the first two leaves to protect fruit from the sun. This is a more common practice in the south, where gardeners are cautious about the intense summer sun.
Prune off all suckers.
Once you decide which way you're going to go, keep these "rules" in mind:
- Wait until plants are almost 2′ tall before pruning.
- Leaves should be dry. Touching wet plants can quickly spread disease.
- Tools should be clean and sharp. I wipe mine down with rubbing alcohol to make sure I don't accidentally spread disease.
- Prune prudently. Leaves create shade for fruit, which prevents sun damage. Leaves also make food for the plant, including sugars, resulting in energy to produce more quantities of sweeter fruit.
- Prune early when suckers are small. This reduces the wound size and also saves the plant's energy, which can be used toward developing fruit.
Here's a tip I've gotten from one of my gardener friends: Late in the season, you can cut the top off of the plants ("topping") to prevent more flower and fruit production, directing energy to ripen the existing fruit on the vine.
By the way, I still love the tomato supports I started using used a few years ago. Re-read the blog as I have made some updates for improvement!