Cordon tomatoes, also known as indeterminate tomatoes, are grown as tall, single-stemmed plants and need regular pruning to maximise fruiting potential and ensure good airflow between plants. Trailing or bush tomatoes (known as a determinate tomatoes) do not need regular pruning.
Why you should prune tomato plants
Cordon or indeterminate tomato varieties are vigorous plants that must be pruned by a technique usually referred to as sideshooting, in combination with training the main stem on a support so plants grow upright. Otherwise, untrained plants would grow along the ground and become a tangled mass of stems that bear fewer fruit and be more liable to diseases and other problems.
Pruning or sideshooting tomato plants also directs the plant’s energy into developing fruit-bearing stems, known as clusters, which are borne on the main stem. This encourages the plant to produce a heavier crop of good-sized fruits. For the same reason, it’s a good idea to prune off the growing tip once the plant has reached the top of its support, which is often done after a certain number of fruit clusters have formed.
Pruning also allows light and air through the plant which enables sun to reach and ripen the fruit and helps discourage diseases.
When to prune tomatoes
[image id=”67966″ size=”landscape_thumbnail” title=”Cutting out large side shoots with secateurs. Sarah Cuttle” alt=”Cutting out large side shoots with secateurs. Sarah Cuttle” classes=””] Cutting out large side shoots with secateurs. Sarah Cuttle
It becomes obvious which branches to cut off tomato plants at an early stage, as sideshoots start appearing on the main stem, just above the joint between the leaves and stem. Start pruning tomato plants, or sideshooting (simply: removing the sideshoots), as soon as you notice these shoots appearing, when they can be snapped off easily and cleanly using your finger and thumb. Do this regularly, once or twice a week, right through the period when your tomato plants are flowering and fruiting.
You will need:
- Sharp snips or secateurs – if you spot the sideshoots early enough, you can simply snap off the sideshoots with your finger ad thumb. However, if you leave them to grow or notice them too late, you’ll need snips or secateurs. These may also be used to cut off the growing tip late in the season.
- Disinfectant-soaked cloth to clean blades, between pruning each plant. This helps prevent the spread of any diseases, such as tomato blight.
How to prune tomatoes
[image id=”33363″ size=”landscape_thumbnail” title=”Removing small tomato sideshoots using thumb and forefinger. Sarah Cuttle” alt=”Removing small tomato sideshoots using thumb and forefinger. Sarah Cuttle” classes=””] Removing small tomato sideshoots using thumb and forefinger. Sarah Cuttle
- Identify unwanted sideshoots that need pruning or snapping off. These grow from the main stem, just above a leaf joint.
- If the shoot is young, grasp it between finger and thumb, close to where it joins the main stem, and snap it off. Repeat over the whole plant. Have a bucket or trug handy to collect the shoots. Or drop them on the soil to break down.
- When using a cutting tool such as snips or secateurs, wipe the blades with a disinfectant-soaked cloth between pruning each plant, to avoid possible transfer of diseases.
- Combine sideshooting with training your tomato plant. For plants that are supported by string or canes, simply wind the main stem around it. Tomato plants growing on rigid supports such as trellis need to be tied in with twine. The same approach applies for pruning tomato plants in pots or growing in the ground.
- Later in the season, as your tomato plant matures, cut off any yellowing or dead leaves where they join the main stem – the leaves close to the ground tend to yellow first. Remove dense foliage that is overshadowing fruit trusses, so sunlight can reach and ripen your tomatoes.
- Remove the growing tip of your tomato plant once it reaches the top of its support. Or, after a certain number of fruiting trusses has developed – four trusses on plants growing outdoors or seven trusses for plants growing under cover. This prevents the formation of more fruits that won’t develop sufficiently by the end of the season.
Things to avoid when pruning tomatoes
[image id=”12183″ size=”landscape_thumbnail” title=”Watering a tomato plant. Sarah Cuttle” alt=”Watering a tomato plant. Sarah Cuttle” classes=””] Watering a tomato plant. Sarah Cuttle
- Avoid pruning when the foliage of tomato plants is wet, as water droplets can transfer disease spores around the plant and on to neighbouring ones
- If you prefer, wear thin gloves to avoid staining your hands and smelling strongly of tomato
Frequently asked questions
Can I prune my tomato plant when it is wet?
It’s best not to. Wait until the foliage is dry before pruning your tomatoes, to avoid the risk of spreading diseases such as blight or grey mould. Working with wet plants is less pleasant, too, especially tall ones that create showers of water droplets.
Should I prune my tomato plants when they are fruiting or flowering?
Yes. Pruning or sideshoot removal should be done every few days, from when flowers and then fruit clusters form.
