Gardening: How to save dahlias hit by frost | Brian Kidd

This is the time of year when there are some awful jobs to do and one of these is to dig out the dahlias which have been scorched by frost.

Saturday, 9th November 2019, 6:00 am
Dahlias - lovely... until they get frosted.

Quite a few areas around Portsmouth have not had a frost yet.

However, here at Waterlooville we had a nasty one a week ago and although I was hoping the frost had not killed the dahlias – it has.

The stems, leaves and flowers have all turned brown and that really is the end of another summer.

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This damage has brought back fond memories of my childhood.

My dad grew lots of dahlias and he always told me they would be killed off by frosts before bonfire night. He was right.

We always allowed the stems to dry off and then used them on the bonfire to lighten the night sky in our garden. Wonderful memories. I had a lovely mum and dad.

Some varieties of dahlias seem to be hardier than others.

To explain: If you left dahlias in the ground last winter and they grew again last spring, these would appear to be hardy.

However, if you bought new varieties, they will have produced lovely tubers (swollen roots) but if left in the ground they may become frozen during the winter and they won’t grow again next year.

But we can save them and here’s what to do.

Cut the stems down to just four inches above the level of the soil. Cut the old stems into short pieces and put them into the compost heap.

Now dig out the tubers and wash off all the soil. Make sure you do this on a nice day. There’s nothing worse than doing it in the rain.

Then tie a label on to the stem. If you cannot remember the name, put the height and colour on the label. You’ve no idea how pleased you’ll be next year that you have adopted my labelling regime!

Leave the tubers in the sun (yes, we do occasionally have a glimmer of sunshine at this time of year) for a day and then put them into the compost from a growing bag which you  used for tomatoes, covering the tubers with two inches of compost.

If there any signs of rings of brown downy mildew on the stems, puff on some sulphur powder. This will stop the fungus spreading.

The tubers are best kept in deep trays. There are some used for mushrooms and these can often be found at the market – just ask the bloke if you can have some.

Keep the tubers in a frost-free place all winter and keep the compost dry.

At the end of February, sprinkle water on to the compost and as long as the weather is warm, new shoots will appear.

Great! We are off to another brilliant summer and dahlias are one of the best flowers for displays from early July right up until the autumn frosts strike.

Dahlia flowers were really good this summer and they provide ground cover all through the summer.

Let’s hope they will be just as good as ever.

Have faith, they will!


If your borders look a little dull, cut some sprays of evergreen shrubs and poke them into the ground. This faux ground cover will look good for several weeks.