Prune Your Tomato Plants for a Better Harvest

Of all the fruits and veggies you can plant and grow on your own, none can you taste the difference in more than tomatoes. The flavour level of something you buy at the supermarket compared to bellissimi pomodori picked from your own plants just doesn’t compare. There’s a unique aroma and freshness to backyard tomatoes that just screams summer – and anyone who’s grown up with a garden, or started one of their own, knows exactly what I’m talking about. It’s the smell, the taste and the texture that justifies trying to grow all the endless varieties of tomatoes for salads, sauces, freezing and jarring. And that's also why it’s not uncommon to see the gardens of some Nonni and wonder  “who could possibly need 50 tomato plants?!”

No matter whether you grow tomatoes in raised garden beds, directly in the ground or even in containers – or whether you stake, trellis, cage or let them sprawl – there are a few simple pruning tasks that will give you better production. So, let’s get into what you need to know about your tomatoes and how you can help them along.

What type of tomato plant do you have?

This is the first thing to consider, because there are two types of tomato plants. “Determinate” tomatoes are bushier plants, usually maxing out at 3-4 ft tall that generally produce all their fruit at once. This makes them ideal for canning, jarring or freezing and also for growing in pots or small gardens. Because they grow to a set size, you NEVER want to prune off anything other than dead or diseased leaves. “Indeterminate” are vining tomato plants that don’t stop growing until they're killed by frost. Most heirlooms, slicing, cherry and beefsteak tomatoes are of this type. These plants can grow up to 20 ft tall with enough time and the right conditions, but usually reach 6-8 ft in zones with a 5 to 6 month growing season. New leaves, flowers and fruits are produced from the top of the plant as it grows, but also side shoots called “suckers” – more on those later. If you’re not managing the plant’s growth it can quickly get out of hand and give you more leaves than actual tomatoes.

Why Prune?

Pruning tomatoes has many benefits leading to better overall fruit quality and plant health. Selective pruning of leaves stops the spread of disease and fungus and even prevents it by increasing airflow around and between plants. Fewer leaves higher up the plant gives ripening fruits access to sunlight. 

Pruning off suckers from indeterminate tomatoes focuses the plant’s energy and production into the flowers of the main stem rather than growing more leaves and side shoots. This is especially beneficial late in the growing season to ensure that small fruits mature on time to be picked before the plant dies. 

How to Prune Tomatoes

You don’t need anything fancy to care for your tomatoes. Handheld pruning shears are nice, but any pair of scissors or even a knife will do just fine. When leaves and suckers are small, they can be pinched or broken off just with your fingers. Cutting is ideal when they get larger, to ensure clean separation and prevent any unnecessary damage to the rest of the plant.

What Parts to Prune

For both determinate and indeterminate varieties, once the plant is approximately 18-24” tall it's a good idea to remove the bottom 6-12” of leaves from the stem; specifically any leaves that are touching the ground or all leaves below the first set of fruit. These lower leaves are especially susceptible to disease due to water splashing from the soil. Throughout the summer any other leaves that turn yellow or look unhealthy should be removed, no matter where they are on the plant. 

With indeterminate tomato plants, the removal of leaves should also continue up the plant as you pick fruit off, so that none of the plant’s energy is being directed to old growth sections. In addition, all side shoots – suckers – should be removed. Suckers look like small tomato plants that grow from the elbow between leaf branches and the main stem. While there’s no direct harm in keeping them, they will act as additional leaves which impair sun and air while also dividing the plant’s resources – giving you smaller fruits. Ideally it's best to remove these when they are short and tender as the longer you wait, the more energy has been wasted by the plant in growing them out. 

Towards the end of the growing season, you should also consider “topping” your indeterminate plants. Basically you cut the top few inches of growth off the plant to ensure any fruits forming below it will reach maturity on time. This is like throwing in the towel on the season and is always a hard act for gardeners to undertake, but it’s better to have a few last red fruits than a basket full of underdeveloped green ones. 

Will you try pruning your tomatoes this year? If you need help deciding what tomatoes to plant, there are garden plans for you. If you want an in-person demonstration on how to care for your garden, let me help with garden coaching. And if you need your backyard garden built, book a consultation today. 

Buon giardinaggio!