When and How to Prune Indeterminate Tomatoes For the Best Crop

Indeterminate tomato varieties produce vines that multiply and lengthen starting early and continuing throughout the growing season. Good pruning practices result in healthier, easier to manage plants and a quality harvest of ripe fruit. Early pruning limits the plant's vigorous, sprawling growth habit, while late pruning focuses energy into growing the biggest, best tasting tomatoes.

Here's what to know about when and how to prune indeterminate tomatoes for good growth and a large, healthy yield.

Why You Should Prune Indeterminate Tomatoes

Indeterminate tomato plants start out with one main stem that rapidly begins to make secondary stems. These stems eventually become vines that produce flower clusters along both sides, continue to lengthen, and produce tertiary vines with more flower clusters.

Both early pruning and weekly pruning throughout the season are management techniques to reduce the number of vines for better control. Over pruning can limit the size of harvest. Though some gardeners say pruning an indeterminate tomato plant isn't necessary, there are advantages to controlling the sprawling growth, including:

• Better disease resistance
• Improved air circulation
• Larger fruit
• Earlier ripening
• Sturdier vines less prone to cracking or breaking
• More easily adapted to cages and staking
  

When to Prune Indeterminate Tomatoes

There are two times to prune indeterminate tomatoes: early in the season when the plant is growing its foliage, and later when the end of the growing season is near. Because pruning needs depend on the stage of growth, how you prune early in the season will be different from later in the season.

Pruning the first few weeks of vegetative growth or throughout the growing season is called suckering. Some indeterminate varieties are more prone to making suckers than others. How long and how much to remove suckers will be a personal preference.

It's best to remove suckers when they are small, 2 inches or less in length. (Suckers are stems that grow at the junction of the main stem of the plant and a branch.) Attempting to remove large suckers can result in stripping or weakening the adjacent vines.

Early Pruning For Indeterminate Tomatoes

Early in the season there are two ways to prune indeterminate tomato plants. One method is to prune your plant to one productive main vine and several secondary vines during the first few weeks of active vegetative growth. The second method allows two main vines to establish with selective pruning of secondary and tertiary vines throughout the growing season.

1. Regularly Inspect Plants

   • As soon as vegetative growth takes off, check your plant every few days to locate new stems/suckers.
   • As fruits begin to develop, reduce how often you check to once a week. (The plant usually makes fewer suckers because less energy is directed into vegetative growth.)

2. Prune for a Single or Double Main Stem

   • To establish a plant with a single main stem, remove all suckers that appear between the main stem and side branching.
   • To establish a plant with a double main stem, select a stem/sucker close to the base of the plant to continue growing and remove all others between the main stem and branching.
     

3. Remove Suckers

   The easiest and most efficient way to remove suckers is by pinching them out with your fingers.

   • Use your thumb and forefinger to grasp the sucker at its base and pinch it off.
   • Pinch it twice if you didn't get the whole thing in the first pinch; failure to remove the entire sucker allows it to regrow into a new vine.

4. Continue Suckering

   • Continue to remove suckers from the main and secondary vines until the plant has reached the desired size, number of vines, and amount of fruit production. Keep in mind that each time you remove a sucker you are removing a potential flowering vine.
     

Late Pruning for Indeterminate Tomatoes

Late pruning is done in autumn as temperatures drop, around six to eight weeks before first frost. Vines are cut back and flowers and small fruits that won't ripen are removed, allowing the plant to direct energy into ripening mature tomatoes.

1. Remove Unproductive Vines

   • Use hand pruners or snippers to remove all vines without fruit, cutting at the base of the vine.

2. Cut Back Vines to Viable Fruit

   • Identify fruit with the best chance of ripening before frost.
   • Use hand pruner or snippers to cut the vine back to just above the junction of the fruit cluster.

3. Remove Flowers and Small Fruits

   • Pinch off new flowers.
   • Use the snipper to remove any small fruits that won't ripen before first frost.