How (and why) should I protect plants from late frost?

Growing your own herbs at home is a simple way to get into gardening – and reap the rewards of fresh mint

Wrap up: use horticultural fleece – or old bed sheets – to protect tender plants Credit: Gary Smith

If you love your garden but need advice on how to keep it looking lush and welcoming all year round, top head gardener Tom Brown can help. In this regular column he demystifies common gardening problems, explains what to tackle when, and shows how to make every moment on the plot more fun and productive. Happy gardening! 


How (and why) should I protect plants from late frost?

Late frosts can be very costly for gardeners. Warm, bright spring days can fool us into a false sense of security and as the sap rises, our urge to dash to the garden centre to buy lots of young plants and flowers becomes hard to control.

The danger lies in the likelihood of late frosts, which can damage and kill tender plants. This includes all plants that have been tended by nurseries in heated greenhouses: they then face the stark reality of a night outside in freezing temperatures when we get them home. Late frosts can occur until the end of May, so the trick is to look after tender plants until the risk of frosts has passed.

The last frost is a turning point in the gardening year – suddenly it’s all systems go – but sadly this date is not fixed and we need to be sensitive to its timing (approximate dates vary depending on area, local gardeners’ forums or word of mouth is often the best guide).

That final frost signals when we can plant half-hardy bedding and vegetables outside (and conversely, the first frost in autumn signals the end of the growing season for those plants).

Try to avoid buying tender plants until the middle of May, but if you can’t resist, then make sure that you have a greenhouse or porch that is frost-free to house them until the risk of freezing temperatures has passed.

During these few weeks, I am obsessive about the weather forecast and if freezing temperatures are predicted, I’m out there in my greenhouse with sheets of bubble wrap and horticultural fleece to cover my seedlings and give an extra degree or two of warmth to help them through the night.

Old bedsheets and net curtains can work equally well; just make sure that you have a few upturned pots around plants to prevent the protection from coming into direct contact with the leaves – we want a little air between the plants and the sheet. And don’t water excessively just before a cold night: plants are much better equipped to get through a chilly spell if they are on the drier side.

Horticultural fleece is available from many stockists online, Harrod Horticultural being one. A 6.5ft x 33ft sheet is available for £12.95 (harrodhorticultural.com).