Monty Don has issued a warning to gardeners about planting tomatoes in May, urging them to resist the temptation to move them outdoors too soon. The gardening expert advises that tomatoes should only be planted in a greenhouse at the start of the month, with outdoor planting delayed until late May.
According to Don, tomatoes struggle with temperature fluctuations, and May nights can remain chilly even when days are warm. 'This is because tomatoes hate too much temperature fluctuation, and May nights can be chilly – especially if the days are warm,' he wrote on his blog.
Fellow gardening expert Jane Perrone agrees, calling early outdoor planting the 'number one error' in May. 'Tomatoes stop growing once the temperature drops below 10 to 12°C at night, and ideally they need 15°C in the day,' she said. 'And frost will kill them, so wait till the frost risk is completely over before sending them outside for good – which is the end of May in my neck of the woods, which is southern England.'
Planting tomatoes outside too soon can hinder growth, disrupt pollination and lead to lower-quality fruit. It also raises the risk of fungal diseases due to moist conditions. Waiting until late May reduces the chance of frost damage as the weather becomes sunnier and warmer.
For those planting tomatoes in a greenhouse now, Don recommends using a pot at least 30cm deep and mixing plenty of compost into the soil. 'Plant them deeply, burying them right up to the bottom leaf, as the buried section of stem will develop extra roots,' he added.
