How to Prune Tomatoes

Growing tomatoes is likely one of summer’s most common garden projects. Who can resist picking a vine-ripened ‘mater that’s sweet, juicy and warm from the sun? Gardeners love to swap tips for growing tomatoes, and each one promises bigger and more tomatoes per plant. One technique that actually helps improve tomato plant yield is pruning.

Why should you consider pruning tomatoes? Five simple reasons:

• bigger tomatoes
• more tomatoes per plant
• earlier tomatoes
• reducing disease outbreak
• eliminating pest hiding places

Know Your Tomato

To get the most out of your pruning, you have to know what kind of tomato you’re growing: indeterminate or determinate. This info is on the plant tag or seed packet. 

Indeterminate tomatoes are tall and vining, and plants need substantial stakes or tall cages. These are the plants that keep forming fruit until the very last frost. Common indeterminate tomatoes include Better Boy, Cherokee Purple and San Marzano.

Determinate tomatoes form a bush that usually tops out between 3 and 5 feet. Plants tend to ripen their fruit all at once, which makes them a great choice for canning or making salsa or sauce. Common determinate tomatoes include Rutgers, Celebrity and Bush Early Girl.

How to Prune Indeterminate Tomatoes

Tomato plants form a growing stem that pops out of the crotch where a leaf attaches to the main stem. That little shoot is known as a sucker (above). If left alone, a sucker forms a large stem that flowers and bears tomatoes. Let all the suckers grow, and your tomato will form a large bushy plant with many small tomatoes. The extra leaves reduce air flow through the plant, which can lead to disease outbreaks. Lots of leaves also give pests like the tomato hornworm plenty of hiding places. Remove suckers judiciously, and your plant will form larger, fewer fruits toward the top of the plant. 

On indeterminate plants, remove all suckers that form between ground level and the second flower cluster. Remove suckers when they’re smaller than a pencil width. If you catch them when they’re small enough, you can easily pinch them with your fingers. Monitor plants weekly until you get all the suckers. If you miss one and it has grown thicker than a pencil, leave it alone. Cutting thick suckers creates open wounds on a tomato that are easily attacked by pests and diseases.

On indeterminate plants, remove all leaves underneath the first fruit cluster. This helps to slow disease outbreaks on plants. Also add a thick mulch layer beneath tomato plants to keep diseases that live in soil from splashing onto lower leaves during summer storms.

How to Prune Determinate Tomatoes

Many gardeners don’t prune determinate tomatoes (above), especially in regions with short growing seasons. But in areas where tomato blight is rampant, pruning suckers that form below the first flower cluster improves air flow inside the plant, which can slow disease outbreaks.

On determinate plants, it’s also good to remove any leaves touching the ground, along with any that are yellow or sickly looking.