

These timings, however, vary with geographic location and weather, so it is possible to plant out in early to mid-May with earlier sowings. Later sowings are also possible – up until late May with varieties like ‘Veranda Red’ – to yield a good crop in October. The tomato plants should be ready to plant outside by the end of May or early June when the threat of late frosts is minimal,' advises Jill Vaughan of Defland Nurseries Ltd, a member of the British Tomato Growers’ Association (opens in new tab). In general, 'if you’re growing tomatoes from seeds you can sow indoors any time from March to the end of May.

The soil should also be warm enough – ideally 60☏ (16☌). It is important to remember that tomatoes are warm weather plants and will not grow in temperatures below 50☏ (10☌). What month to plant tomatoes will depend on your climate and growing zone as well as whether you plan to grow them outside or in the greenhouse. (Image credit: Getty Images) What is the best month to plant tomatoes? Look out for signs of disease so you can adopt tomato blight treatments as necessary for outdoor-grown tomatoes, although you should be aware that it could also strike greenhouse-grown plants. Remember that pruning tomato plants if they are indeterminate – cordon or vine – varieties is a task worth undertaking once the plants are large enough. 'Make sure to slowly expose them to the outdoor world over the course of one to two weeks before planting them directly in the earth to allow them to adapt to direct sunlight, wind, and temperature changes,' she says. In order to be planted outdoors young tomato plants should generally be around 9 to 12 inches tall (23 to 30cm) and will require a phase of hardening off advises Annie Singer. Whether they are ready to be transplanted outside will depend on the size of your plants, too. 'Tomato seedlings grow very slowly at temperatures below 50☏ (10☌) and may be damaged at temperatures below 43☏ (6☌).' This usually occurs a few weeks after the local last frost date,' says gardening blogger Mary Jane Duford. Most tomato plants are planted outdoors when nighttime temperature lows are at or above 50☏ (10☌). 'Tomatoes are usually transplanted outdoors zero to four weeks after the last frost date in your local area. The answer is that the plants should be transplanted outside once the risk of frost has passed and the soil is warm – this will depend on your growing zone and weather conditions. Consider companion planting tomatoes to boost the harvest as well as deter pests. If they are sown under cover, the question of when to plant tomatoes outside is important. (Image credit: Burpee Europe) When to plant tomatoes outside
