When to repot tomato seedlings if you want to give this garden staple the best possible start

There's nothing better than homegrown food tastes, quite frankly – especially when that homegrown food is a bowl of ripe and juicy tomatoes. Ideally with a good glug of olive oil and pepper, for good measure.

While these Mediterranean fruits are very easy to grow, though, you need to learn exactly when to repot your tomato seedlings if you want them to taste their very best come harvest time. 

That's right: it's no good learning how to grow tomatoes if you aren't prepared to work with their schedules. So, once you've managed to sow your seeds successfully, here's exactly how long you need to wait before you move your tomato seedlings on.

When to repot tomato seedlings

It doesn't matter if you grow tomatoes in pots, in grow bags, or straight in the soil: it's best to start your seeds off in pots somewhere warm until they've evolved into strong little seedlings.

Still, when it comes to repotting your tomato seedlings there are quite a few factors to keep in mind.  

'It is important to understand what sort of tomato you are growing,' says Joseph Clark (as in, yes, he of @JoesGarden fame!). 

Joseph Clark

With some 25 years of gardening experience under his belt, Joseph Clark utilises his abundance of innovative ideas to create easy and fun recipes to help his audience lead more healthy and environmentally-friendly lives whilst also saving money. He recently penned a must-read book called Garden To Save The World: A Feel-Good Guide to Growing for Yourself, Your Plants and the Planet. 

Joseph goes on to explain that there are two types of tomato: vine and bush. And, while many of the rules remain the same for both when it comes to repotting their tomato seedlings, he says that there are a few differences. 

1) Repotting the seedlings of vine tomatoes

As the name suggests, vine tomatoes grow from a single vine. 'They can reach 2 metres tall and as such need to be transplanted with that in mind,' says Joseph. 

'Once your seedlings have formed their first set of true leaves (the leaves that form after the two original germination leaves), you should gently move them into a larger pot, no smaller than 7cm in diameter,' he continues. 

'It is a good idea to scoop the roots out with a spoon, while holding a leaf not the stem, and water really well. Try to grow these plants on in this pot until they are around 15cm tall. Only then will it be time to think about transplanting your vine tomato seedlings into their final growing position.'

Where to buy vine tomato seeds:

Joseph goes on to note that tomatoes will always grow best in a warm sheltered sunny spot, and, while some varieties will be fine outside, many will appreciate the protection of a greenhouse or polytunnel. 

'Wherever you choose to grow them, make sure the final growing spot has a deep enough level of quality compost,' he says. 'Once this is done, remove your tomatoes from the 7cm pot, and trim away the bottom set of leaves.'

He adds that he prefers 'to bury the plant at least 8cm deep, as this will allow the plant to develop a much healthier root system, which in turn will give you a much healthier plant'. 

2) Repotting the seedlings of bush tomatoes

When it comes to bush tomatoes, Joseph says that he follows the same process – with a few minor tweaks.

'They do not need the lower leaves removed, and they don't need to be buried as deep as a vine tomato, as the plant will usually only grow to 30cm in height,' he explains. 

'Bush tomatoes are best planted into pots no smaller than 10l, and they can even thrive in hanging baskets.'

FAQs

When should I move tomato seedlings to bigger pots?

'As tomato seedlings grow they will need potting on before they are eventually in their final growing position,' says Morris Hankinson, director of Hopes Grove Nurseries. 

Morris Hankinson

Morris Hankinson is the founder and managing director of Hopes Grove Nurseries Ltd, the UK’s only specialist grower-retailer of hedging plants. He established the thriving business in 1992, shortly after graduating with a Commercial Horticulture Degree from Writtle College, Essex. 

'When the seedlings are about 10cm tall with a full set of true leaves, carefully transplant seedlings to individual small pots filled with peat free compost,' he continues. 

'Use a dibber from Amazon to gently lift them from the compost and replant them into the larger pot. As the stems get taller, use small canes or pea sticks to support the growth.'

Morris adds that, each time you pot up tomatoes, you should plant them quite deeply so the first set of leaves is just above the soil. 

'The stems under the soil will produce more roots giving them strength and good growth as the plants get bigger.'

How do you know when to repot a tomato plant?

'Your seedlings are ready to pot on from the seed tray once they are around 7cm tall and have developed a strong set of true leaves,' says Joseph.

'After all frosts have passed, they can be moved into 30cm pots for greenhouse or outside container growing,' adds Morris. 

'Don’t forget to include some supports at this point such as bamboo canes from Amazon.'

How do you repot seedling tomatoes?

When the time is right to repot your tomato seedlings, Joseph says 'it is always best to keep the root ball in tact'. 

'My favourite way to do this is to use a spoon or fork to scoop out the whole root ball with minimal disturbance,' he says.

'Then, when transplanting, be sure to hold the leaves and not the stem to avoid damaging the plant.'

If your tomato seedlings are growing really tall but are spindly and struggling to support their own weight, Joseph adds that they most likely need more sunlight. 

'When transplanting, make sure to water the plant well afterwards, and keep the soil moist throughout the growing season,' he says.

'It is vital all risk of frost has passed before planting tomatoes outside. Tomatoes are tender plants and any frost will be a disaster for them.'

Finally, Joseph says to be sure to bury at least 40% of your plant when transplanting vine tomatoes to their final growing position to get the best root system possible. 

Now that you know when to repot tomato seedlings, you're well on your way to the perfect harvest – so long as you give our must-try tomato tapping hack a go, of course.

Hey, these little beauties may need a lot of TLC, but it'll all be worth it when you bite into that first succulent homegrown tom. We promise.