The best time for when to plant tomatoes in the UK is around the end of May unless you want to grow from seed. No chance of growing from seed at this time of year because you would have to add a further 4 to 6 weeks onto the schedule and you just haven’t got enough time left to do that.
So if you haven’t already cultivated your tomato plants from seed so they are ready for the end of May, you will have to go and buy some tomato plants and quickly. Because they need to be in the ground, a growbag or a 12″ plant pot no later than the 1st week in June.
You also need to consider how long the tomato plants take to mature, they tend to come in 3 groups
- early season varieties, no more than 60 days
- mid season varieties, no more than 75 days
- late season varieties, no more than 90 days
It is the size of the tomatoes that primarily dictates how long they take to mature, cherry tomatoes generally slot into the early season variety, mid size such as plum tomatoes tend to go in the mid season grouping and larger tomatoes like beefsteak fit in the late season group. It’s a good idea to have plants from the different varieties to ensure that you have tomatoes maturing throughout the whole season.
Taking into account when you are likely to see the last frost of the winter, you can actually stagger when you get your plants into their final spot to further extend the season. Realistically you are probably only going to be able to steal another month because even after April has passed there is still a bit of a chance of a late frost.
We actually saw snow this year in the South of France during the first week of May, a bit of a disaster from the tomato growing perspective, especially if you are planting straight into the ground. So as they say in Yorkshire, ‘ner cast a clout till May is out’ which means don’t remove any clothes until May is out (out meaning arrived) so literally you need May to have arrived before you can consider the cold weather has completely finished. this year being an exception to that rule; so much for global warming.
So in summary the time to plant tomatoes in the UK is during the month of May, but taking care not to be caught by a late frost at the beginning of May. Seeds need to be being cultivated around 4 weeks to 6 weeks before that, depending on variety which puts you at the middle of to the end of March. In the UK that might mean you need to start your seeds indoors or in a heated greenhouse to get the ideal germination temperature of 16C (61F), but hopefully by then you will be OK.
Of course if you have the facilities available such as a heated greenhouse, you can start seeds much earlier perhaps around the end of January, but you will need to be able to protect the subsequent plants from frost as they are likely to be ready at the beginning or middle of March. They will also need some reasonable periods of sun, ideally at least 6 to 7 hours a day, not always easy to come by during March, but still feasible although they may be a little slower maturing.