Overwintering Dahlias

I spent the weekend finishing off one of my biggest autumn jobs – overwintering dahlias.

They could be left in the ground as my sandy soil is well-drained but I prefer to lift them as I grow them in a different bed in the veg plot each year.

I also find that growing them in pots until they’re big enough to ‘scare’ the slugs and snails reduces the chances of finding a dahlia disappearing overnight – it has happened in the past.

If you do leave them in the ground, cut the plants down and give them a good thick mulch to protect the tubers.

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It’s been a good year for the dahlias and I was really pleased with this season’s new varieties – in particular the two above. ‘Penny Lane’ was bought for the name but what a fabulous flower it turned out to be. ‘Crème de Cognac’ was another stunner – I really liked the two-tone flowers.

For me, overwintering dahlias begins when the first frost blackens the plants. That happened a couple of weeks ago, although they survived a couple of light frosts first.

The first thing I do is cut off all the foliage, which then goes on the compost heap.

I leave a length of stem – as much as anything it gives me something to hold onto when handling the tubers.

I put all the tubers into individual pots, upside down to let any water drain out of the stems, having removed as much soil as possible.

These were then put into the potting shed for a week to dry out a little. The most important thing is to remember to put the label in with them as one tuber looks very much like another!

Throw away any tubers that are soft or going mouldy. I did have a couple of casualties, which is unusual. Replacements will now be going on my shopping list.

One or two of my container-grown dahlias have just been put into a frost-free place and will be left in the pots, unwatered, until the spring.

After the rest of the tubers had spent a week upside down in the potting shed, it was just a case of turning them the right way up and covering them with some dry compost – I used the old compost from this year’s tomato pots but other people use newspaper, sawdust, or vermiculite. They can be done individually or put into trays – just make sure they’re clearly labelled! You are trying to strike a balance between the tubers drying out and rotting because they are too wet.

My overwintering dahlias are now tucked up in the potting shed but a garage would do the same job. It just needs to be somewhere that is frost-free. I will cover the pots with some fleece if the temperatures plummet.

Looking at the forecast, it seems I got this job done just in time as we may have sleet next week.

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