How to prune tomatoes and not kill your plant

You’ve planted your very first indeterminate tomato plant. You know you need to start pruning your tomato vines…but you’re worried you might accidentally kill your tomato plant. Don’t let fear keep you from snipping away the suckers or taming the vines. This guide will help you learn how to prune tomatoes to keep your vines alive and healthy. 

What do you mean by indeterminate?

When looking at the baby tomato plant options, you’ll probably see the words “determinate” or “indeterminate” on the labels. This lingo is letting you know what to expect from the plant: 

• Determinate = bush  
  • Grows to certain size, ripens fruit at about same time, minimal support and pruning required
• Indeterminate = vine  
  • Keeps growing until frost, fruits throughout the season, needs trellising & regular pruning

In this tutorial, we’ll be focusing on indeterminate tomato vines and how to properly prune them.

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Why prune tomatoes?

Indeterminate tomatoes left to their own devices will turn into an impenetrable jungle (speaking from experience here), but there are also other benefits to pruning tomatoes than aesthetics–preventing disease and more fruit production.

Soil-borne bacteria or fungus start down below, so keeping the tomato leaves clear from the dirt is a simple way to prevent a myriad of blights and disease. Tomato vines also need good air circulation to prevent humidity-related molds/fungus growth on leaves.  For more tomato disease information, check out your local extension service’s website.

We don’t grow tomato plants for their leaves (at least I don’t!), we grow them for their juicy fruit. So pruning away extra leaves will encourage the plant to put more of its energy into tomato production. Keep that in mind when it seems like you’re cutting off a lot of leaves and stems–it means you’ll have bigger and better tomatoes rather than lots and lots of leaves.

Tools

• Pruners
• Garden Scissors
• Your hands

No fancy tools required, but be sure to wash and disinfect your pruners or garden scissors after use to prevent passing along disease to other nightshade family plants or transmit harmful bacteria the next time you go to prune your tomatoes.

How to prune tomatoes

Step 1 – Trim away from the soil

Many tomato diseases and blights live in the soil, so the first step is to trim away any stems or leaves that are low to the ground or touching the soil. Remove all leaves from about a foot up from the dirt.

Step 2 – Trim off discolored leaves

Pruning is also the time to trim off any yellowing, spotted, or otherwise discolored leaves you may see. Removing any potentially infected plant material should help prevent the spread of disease. Don’t compost diseased leaves and be sure to disinfect your pruners before pruning your next plant if you suspect disease!

Step 3 – Pinch or snip off suckers

I’ll include a photo, but as the vine grows, between the branch and the vine, essentially the start of another baby plant will pop up. Pinch them off if they are small or use a pair of pruners to snip them. Just don’t prune the very top growing tip of your tomato!

Step 4 – Fasten to trellis system

Tomato vines grow all different directions and this is a good time to re-tie or fasten the vine to your trellising system. Last year we used velcro strips to tie them to hog panels. This year we hope to try the hanging-string method of growing tomato vines (will report back later!) Whatever trellising method you decide to use, tying them up while going through pruning makes for an efficient workflow.

How often to prune tomatoes?

A quick weekly prune and trellising session would be the ideal. But we know how easily life can get in the way of good intentions! We personally aim to tame our tomato plants at least every other week or so. Sometimes the suckers get bigger than we can pinch with our fingers, so we pull out the snippers and hack them back. Thankfully tomatoes are forgiving plants and typically still produce plenty of tasty fruit despite some neglect!

Oops! I cut off the top!

Did you accidentally cut off the growing tip of the tomato plant? No worries! If you are nearing your first frost date, snipping off the top is actually a good idea to encourage the tomato plant to finish setting and ripening fruit before the cold arrives. If you still have more time in the growing season, pick a good-looking sucker and treat it like the growing edge of your vine from now on.

Hope this guide helps you prune your tomato plants with confidence this growing season. For more gardening tips check out our other blog posts.