If you planted before the last frost, don't panic! This is how to protect tender plants until the warmer weather returns

Last week’s sunny spell had lots of us out in the garden, and my local garden centre was the busiest I’ve seen it in months. Now the frosty mornings have returned, you might be wondering what to do with the tender plants you planted too soon.

Well, don’t panic — there are plenty of fruits, vegetables and flowers you can plant in March, and the colder weather won’t sabotage all of them.

Less hardy and tender plants are at risk, though — but thankfully, there are lots of ways you can protect plants from frost until the weather warms up again.

If you jumped the gun and started planting tender varieties last weekend, it’s understandable — the sunny weather tricked us all.

That said, there are plenty of bulbs you can plant in March, and even a handful of beginner-friendly vegetables that you can sow in March (usually indoors or in a cold frame). But what about the less resilient plants?

‘Most summer plants are tender and don’t tolerate the cold,’ says Josh Novell, Polhill Garden Centre's garden plants expert and director.

‘If you’re unsure, check your plant's hardiness rating, which indicates the lowest temperature a plant can withstand.'

Luckily, you can still protect tender plants with a few trusty outdoor plant covers.

‘If I’m covering my plants or shrubs, my favourite way of protecting them from the elements is by making a tent-like structure around them,’ says Chris Cooper, senior product marketing manager at Hayter. ‘I use horticultural fleece for this, then peg it into the ground with stakes. It’s as easy as that!’

It’s also too early to unwrap most tender plants — so if you’ve already got them covered, hold off until the risk of frost has passed.

Where to buy plant covers

Josh is a fan of horticultural fleece, too. ‘One of the best options is to cover them with frost cloth or garden fleece as it helps to trap the warmth,’ he says. 'Make sure the cover reaches the ground to keep the warmth in.'

If you don’t have horticultural fleece to hand, you can use old towels in the garden, or old bed sheets. ‘Just ensure they're not too heavy, as they may weigh the plants down,’ Josh adds.

Wrapping and covering plants isn’t the only way to insulate them — you can protect plants with mulch, too.

‘Mulching around the base of the plants helps to insulate the soil and protect the roots from freezing,’ says Josh. ‘You can use materials like wood chippings or straw.’

Where to buy mulch

So, when is the best time to plant tender plants outdoors?

‘To be safe, wait until early June before planting tender plants outdoors,’ Josh advises. ‘If you’re eager, start them indoors and gradually expose them to outdoor conditions as the risk of frost fades. This ‘hardening off’ process helps them acclimatise.’

And, of course, if you’re growing tender plants in pots, you can always move them inside.

‘Stay one step ahead of the frost and keep an eye on the forecast, as this can help you time when you should or shouldn’t bring your potted plants inside,’ says Chris from Hayter.

‘That being said, be careful not to place them somewhere incredibly warm either. The shock of going from intense cold to intense warmth can actually do more damage than if you just left them in the first place. For the safest results, move them into a garage, greenhouse or shed.’

FAQs

How do you help plants recover from frost?

Wondering if you can save a plant that’s been exposed to frost? It all depends on the type, and how extensive the frost damage is.

If you act fast enough, you can save the plant before the frost kills the entire plant and trim away any dead growth — but check the guidelines around the species you have, as pruning out of season could cause even more damage.

So, now you know what to do if you planted before the last frost: stock up on frost protection to tide your plants over until the wintry weather is behind us.