When To Plant Tomatoes Outside In The UK

When it comes to growing tomatoes in the UK, timing is everything! By planting healthy young plants outside at exactly the right time, we maximise our chances of a bountiful crop of delicious tomatoes all summer long. Let’s take a look at when and how to plant tomatoes outside for best results in the UK.

Tomatoes should be planted outside in the UK in late spring after any risk of frost has passed and the soil has warmed enough to promote vigorous root development. This is normally around the end of May in most areas of the UK but can be up to a month earlier in milder southern regions. In the far north and hillier regions, frost can still occur in early June, so it is worth waiting a week or two longer.

tomato seedlings

What happens if you plant tomatoes out too early?

Tomatoes are not frost-hardy; even a mild frost is enough to damage or kill tender young transplants if planted out too early. In addition, these heat-loving plants will not thrive with their roots in cold soil, and growth will be slow and stunted.

What happens if you plant tomatoes out too late?

Because the summer growing season is relatively short in the UK, planting tomatoes out too late will lead to lower yields. The aim is to get your tomato plants in the ground at the perfect time to reach maturity as soon as weather conditions are favourable for fruit production.

Having said that, tomato plants grow rapidly, and there is no harm in planting out good-sized young transplants a few weeks later than recommended. They may not start producing a crop until later in the summer, but you should still harvest a reasonable yield.

When to sow tomato seeds for growing outside

When growing tomatoes outside in the UK, don’t be tempted to sow seeds too early. These tender young plants cannot be planted outside until late spring and must be kept in a warm, sunny place until then. Sowing our amazing quality tomato seeds in late March will allow plenty of time for the seedlings to reach a reasonable size for planting out.

Tomato seeds need consistent warmth to germinate, so use a heated propagator or place seed trays in a plastic bag inside a warm airing cupboard until the seedlings emerge. Young seedlings need warmth and as much natural sunlight as possible for healthy growth –  a south-facing windowsill is ideal. Low levels of sunlight can lead to weak ‘leggy’ plants prone to damage.

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Top Tips For Planting Tomatoes Outside

Tomatoes aren’t difficult to grow outside in the UK, but they do require a bit of mollycoddling to get the best results. The best place to start is by ensuring you have healthy young plants for transplanting – they should be around 6-8” (15-20cm) tall, with a thick main stem and plenty of leafy growth. At this stage, you may even see the first flowers developing.

Young tomato plants are very delicate and sensitive to extreme changes in temperature. To ready them for life outside, start hardening them off – this means moving them outside for a few hours on sunny days, then back indoors overnight when temperatures drop. Continue this for a week or so, gradually extending the time spent outside day by day.

When all risk of frost has passed, plant tomatoes outside in the UK in a sunny spot with shelter from prevailing winds. Tall indeterminate tomato plants can be grown directly in the ground or in large containers or grow bags but will need a stake or tomato cage for support. Bush varieties will also do well in containers and hanging baskets, and their vibrant display of colourful fruits makes an attractive addition to sunny patio areas.

In colder regions or during cooler spells of weather, young tomato transplants can be protected with fleece or cloches. Plastic bottles with the base cut off make a great temporary cloche and can be secured in place with a stake. Gardeners in particularly chilly regions may benefit from warming the soil for a few weeks before transplanting young tomato plants by covering the ground with plastic sheeting or cloches.

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