4 ways to protect plants from a late frost – with a top tip from Monty Don 

Don’t be caught out by an unseasonal spring freeze

Feeling the chill? You’re not the only one. A late spring temperature drop can be a shock to our garden’s system as well as ours. Just as shrubs are regaining their green foliage and saplings pluck up the confidence to poke their heads above the soil, they’re greeted with an icy shock.  
We spoke to Sarah Wilson, horticulturist and founder and presenter of the Roots & All podcastwho has shared her excellent and easy ways to protect plants from a late frost. We’ve also gleaned a couple of tips from presenter and gardener Monty Don, so you can keep your plants snug and ready to bloom this spring.

Apple Blossom with a covering of frostCredit: Doliux/Shutterstock

1. Wrap shrubs and trees in horticultural fleece

Monty Don swears by this trick

Monty Don has a top tip for protecting tender shrubs – such as pomegranates, olive, bay or citrus grown in containers – from frost damage.

As he explains on his blog: “The solution is to have squares of horticultural fleece cut to fit each plant ready to wrap around them. This will be enough protection against light frosts although in really cold weather, when the temperature drops below minus 5, they will need a double layer or moving indoors. I lightly secure them with twine so that the fleece is easy to remove as soon as the temperature rises again.”

“If you’ve got plants that are established in the garden, the best thing to do is wrap them in something,” adds Wilson. “Horticultural fleece is the best thing. Make a tent around them using bamboo canes to prop the fabric up so that it doesn’t touch the plants.” 


2. Alternatively, cover with cardboard or even plant cuttings

Use what you have to hand

“If you haven’t got horticultural fleece to hand you can pretty much use anything, so cardboard, fabric sacking or even discarded plant waste,” says Wilson.

“For example, if you’ve been pruning back ornamental grasses, you can pack that around your plants. Always cover your plants in the daytime so that you trap the warm air in there.”  

3. Bring pots and tender seedlings inside

Don’t leave them exposed

“If you’ve got pots or trays of seedlings outside, bring them under cover for a couple of nights,” says Wilson. “Be wary of a drastic temperature change – an unheated conservatory or a porch would be best, or a garden shed.”

“If that’s not an option, bring them into the house but try to keep them as cool as possible. Even if it’s dark, that won’t hurt them for a couple of days and it’s better than leaving plants at the mercy of the elements.”

4. Place seedling trays on woodchips

Rely on a natural heating system

I have trays of seedlings in an unheated greenhouse but I do use tricks – I wrap them and put them on a bed of woodchips, which generate heat as they decompose,” says Wilson.

“Rotting woodchips give off enough heat to keep the cold off in low temperatures. I’ve got sweet peas in an unheated polytunnel, which gets to minus temperatures, sitting on woodchips and they’ve been going all over the winter – those hardy annuals are pretty tough. I do the same thing with delphiniums and calengulas.

Rose bush covered in breathable material to protect from frostCredit: Ludmila Kapustkina/Shutterstock
Cover shrubs with a breathable material or garden cuttings to prevent late frosts from causing damage

Is it warm enough to plant out?

Not sure if it’s warm enough to start planting out? Then test the soil. If your soil is ready then March is a good time to plant and move things around. But ‘ready’ means, above all, warm enough,” advises Monty Don. “The only way to know this is by touch. Pick up a handful of earth. If it feels cold and clammy to the skin, then seeds will not germinate, and roots will not grow. If it feels warm, holds together when squeezed and yet can easily be crumbled then it is ideal.”

Three things you should never plant outside until the last of the frosts

“Frost reduces dahlias to blackened tatters,” warns Monty Don on his blog. You should start dahlia tubers off in pots under cover, in the greenhouse or on a sunny windowsill, then plant them out in May when all risk of frost has passed.

I wouldn’t contemplate doing anything with your tender plants right now,” says Wilson. “That includes pelargoniums, and anything that needs a lot of sunshine and heat.

If you have pelargonium plants that you’ve brought under cover for the winter, keep them under cover, and avoid planting new plants outdoors until the risk of frosts has passed.

“Runner beans are not worth planting out until May really. There are plenty of things you can plant, but beans are a bad idea,” says Wilson. You can start them off indoors if you want an earlier crop, or plant them in the ground in May.

What to plant out

Wondering what to plant out before the last of the frosts hit? Sarah’s rule of thumb is: “Anything that’s showing around the garden that seeded itself and is popping its head up of its own accord. Now, California poppies, nasturtiums and hardy annuals are just starting to emerge in my garden.”

Amy Cutmore

Written by Amy Cutmore she/her


Amy Cutmore has been writing about interiors for more than 20 years, harking back to the days when glossy red kitchens, toile de Jouy and rag rugs were all the rage, and everyone wanted a Changing Rooms makeover. You’ll have seen Amy’s work at Britain’s biggest homes titles, including Ideal Home, where she served as Consumer, Technology and Group Digital Editor. She has also edited or written for Homes & Gardens, Livingetc, 25 Beautiful Homes, Real Homes, Gardeningetc, Inside Readers’ Homes, Inspirations for Your Home, Country House & Home, Top Ten Reviews, Trusted Reviews and Country Life.

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