How To Train Tomato Plants

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Video Transcript

I find there are three important things to get right in growing tomatoes: firstly, how to train tomato plants so that their energy is concentrated on producing fruit, rather than leaves and branches, which is the subject of this video, secondly, supporting the plants so that when the fruit starts to form the weight of the fruit does not cause the plant to topple over, or the branches to break, and thirdly, consistent watering so that the roots are always moist. If the soil is too dry, or waterlogged, this can spoil the fruit and risk the plant becoming diseased. Links to these other topics can be found beneath the video.

This video is focused on training tomato plants. To begin with, there are two main types of tomato plants: determinate varieties and indeterminate varieties, or to put simply, those that need training and those that don’t. The majority of tomato plants sold are indeterminate varieties that grow tall and need training. They are sometimes called cordon varieties.

Tomato plants that don’t need training, determinate or bush varieties, are mostly cherry tomatoes. These are often sold as container types suitable for hanging baskets. These are relatively small plants, that develop a rounded shape as they grow. Check with the shop when buying seed or plants whether they are determinate types.

Not all cherry tomato plants are determinate types. In fact, two of my favourite tomato varieties to grow, Sungold and Chocolate Cherry tomatoes, are cherry tomatoes that need supporting. If the label does not say it is a bush type, most probably it is a indeterminate or cordon variety that will need training.

I think it’s helpful to understand how a tomato plant grows naturally, before explaining how they can be trained. An indeterminate variety will produce a leader stem that will continue to grow vertically throughout its life. This stem grows from its tip. As the plant grows, horizontal branches will form either side of the central stem, and these provide the leaf mass that helps the plant to grow. For the gardener, the all important fruit trusses spring out from the central stem. What distinguishes these fruit trusses from horizontal branches is that often they have a more upwards growth, and unlike branches, they do not grow in pairs either side of the central stem. Most tellingly of all, they quickly develop flower buds, that will go on to set the fruit.

What I have shown so far is the ideal growth of the tomato plant for the gardener, which is what a plant should continue to look like when it is trained to produce the most fruit. However, if left untrained, a tomato plant will grow much more than this. There are two growth habits that will need to be constrained, or pruned away. The first is the plant producing more than one leader stem growing from the bottom of the plant. If left unpruned, these will grow in exactly the same way as the main leader stem, effectively halving the amount of energy going into the main stem. I find it easy to miss spotting the growth of new leader stems, especially on older plants, as my attention is on the top of the plant and the developing fruit.

The second growth habit that needs to be dealt with are side shoots that emerge from the elbow of the leader stem and horizontal branches. Nearly every elbow will develop a side shoot, and when tomato plants are growing strongly in late spring and early summer, these side shoots spring out and grow quickly. I find that pruning these side shoots is a task that needs doing every two to three days. The side shoots are best removed when they are about two to three inches high. If they are removed younger when they are just small leaves, sometimes they grow back. You may like to see my other video on taking tomato cuttings from side shoots, which is a great way of getting additional tomato plants or sharing your varieties with friends or family. See the link below the video.

If a tomato plant is not trained in this way, very soon a cordon tomato plant will become a big green mass of stems and leaves. It may end up covered in flowers that form small tomatoes, but because the plants energy, as well as water and light, is divided over so many fruit, this often results in a much later harvest and many of the fruit never fully ripening. Supporting so many branches is much more difficult, and when the fruit forms, without support the branches may topple over and break.

I find what works best is to limit each tomato plant to one leader stem, with all the energy devoted to this one stem. It will go on to produce more fruiting trusses, and with luck, all of these will ripen fully. If I want more tomatoes, I will grow additional tomato plants, rather than try and grow more fruit off the same plant.

Towards the end of the growing season, when the tomato plant has reached the top of the support, or the roof of a polytunnel, greenhouse, or conservatory, I pinch out the top of the leader stem to stop it growing further. This diverts energy to the fruit below, and all being well, will result in a large harvest of tomatoes. By training tomatoes in this way and growing inside my polytunnel, I have been able to harvest tomatoes from late June until early November. I hope this method works for you too.