What is overwintering? Meet the gardening technique that can save your flowers from frost

What is overwintering?

If you haven't heard the term before, you've likely asked the above at least once – but, we promise, overwintering is one of those garden ideas that every gardener, no matter their proficiency, needs to know about.

Thankfully, it's a pretty easy concept to wrap your head around. And, better still, once you know what you're doing, you can use all of your new overwintering skills to rescue your favourite flowers from frosts and cold snaps. Win!

What is overwintering?

The clue is in the name when it comes to overwintering, as it's all about helping your plants survive over winter.

'When cold weather arrives, we take measures to keep ourselves warm. We wear extra clothing, put on the heating or light a fire and, if it gets really cold, stay inside as much as possible,' explains Rob Grayson, head of plant distribution at Hillier. 

'We should take the same care of the plants in our gardens.'

When it comes to protecting your plants to try and keep them alive through the winter, it's important to suss out their individual needs. 

Because, you guessed it, the phrase, 'What is overwintering?' will have a different answer depending on the plant in question.

'The specific methods for overwintering can vary depending on the type of plant and the weather,' says Morris Hankinson, director of Hopes Grove Nurseries. 'It may involve bringing plants indoors, insulating them, or providing them with extra protection against freezing temperatures, frost, snow, and ice.'

Morris Hankinson

Morris Hankinson is the founder and managing director of Hopes Grove Nurseries Ltd, the UK’s only specialist grower-retailer of hedging plants, which he established after graduating with a Commercial Horticulture Degree from Writtle College, Essex in 1992.

It is usually most common to overwinter tender perennials. However, if you've been trying to figure out how to overwinter lavender in pots, then you're still on the right track. 

Why? Because, while lavender is a hardier plant than most, plants in pots are always more vulnerable to winter chills than plants in the ground.

'Plants in pots are more at risk from the cold as the entire rootzone in the pot can freeze, especially in a cold snap after a wet period,' says Rob. 

Still wondering what overwintering is? As mentioned already, it will look different depending on the plant you're trying to protect.

'The techniques for overwintering plants can include mulching, wrapping in hessian providing shelter, and controlling watering to prevent root damage caused by freezing and thawing,' says Morris.

Rob adds that herbaceous plants with tender bulbs or tubers, such as dahlias and canna lilies, can be 'dug up and overwintered stored in boxes of peat free compost in the garden shed'. 

'Don’t let them completely dry out,' he adds, 'but remember that keeping them too wet will lead to rot. A light water over the compost once a week should be plenty!'

Of course, when it comes to plants like potted geraniums, the easiest way to overwinter them is to make like the Scandis and bring them inside for coddling during the colder months.

'A cloche or coldframe can also be useful for tender plants in your borders,' adds Rob.

Finally, we'd have failed to answer the big 'What is overwintering?' question if we didn't tell you when to begin the process. 

'To know when to start overwintering your plants, keep an eye on the weather forecast,' says Rob. 'Once overnight temperatures drop below 10-12°C, tender plants will need some protection.' 

FAQs

Now that you've learned what overwintering is, it's time to start sussing out which of your favourite garden plants will need some TLC this winter.

And remember, bright sunny days often lead to cold nights without cloud cover, so be ready!