Overwintering Dahlias – BBC Radio Leicester phone-in questions for Saturday, November 6 2021

Dahlia Nuit D’Ete in my cut flower garden

Dahlias have been fabulous this year, giving masses of cut flowers from mid June until November. We’ve had unseasonably mild weather, which means we still have flowers today. But other areas in the county have had night-time frosts. So now is the time to dig up and protect your dahlia tubers for the winter.

Frost-blackened foliage . Photos taken last autumn.

There are two methods for saving dahlias for next year. You can either dig them up and store them in a frost-free place, or you can leave them in the ground and cover them with dry leaves, straw or horticultural fleece. Leaving them in the ground is only possible is you have well-drained soil. In heavy clay, and or where gardens flood, the tubers will rot.

Method 1. Digging them up:

If you are planning to dig them up, wait until the foliage has been frosted. This makes the dahlias absorb goodness back into the tubers and sends instructions to become dormant.

Using a fork, carefully dig up the tubers, taking care not to damage them. Remember to keep any labels with the tubers. Brush off the soil if you can. If they are wet and muddy you can wash off the soil and use a soft brush to clean them up. Or you can put them in a shed to dry and brush the soil off in a week or two. Washing and brushing helps to remove slugs and earwigs and other soil-borne pests and diseases .

Cut back the stems leaving about 3”. Turn the tubers upside down so moisture drains out of the stems. After a week, turn the tubers the right way up and store them in pots or seed trays. You can use dry compost or horticultural fleece to cover them. Keep them in a cool, dry frost free place such as a garage or potting shed.

Tip: You can plant tulips in the space left behind in the garden. I dig up the tulips next spring to make way for the dahlias again.

Method 2. Leaving them in the ground:

If you have well-drained soil, you can try to leave some dahlias in the ground. In a very cold, wet winter, this is risky.

To leave them in the ground, do not cut off the stems. Fold the stems over and collapse them back onto the tubers, this will stop the stems becoming like ‘straws.’ Cut stems will direct water straight to the tubers, causing rotting.

Cover the tubers with a thick layer of dried leaves, straw or horticultural fleece. I usually try to keep them dry by covering them with sheets of recycled corrugated plastic or old compost bags. Plastic cloches can also be used.

Tubers will be started back into growth next spring.

Here’s some dahlias from my plot. Nuit D’Ete with cosmos and persicaria.

My favourite orange dahlia, David Howard, shown here with chrysanthemum Swan.

Dahlia Evelyn with carnations and senecio grey foliage from the plot.

Dahlias can also be started from seed in early spring . This was from a mixed packet which included lots of jewel-like colours. This summer I’ve grown the ‘Bishop’s Children’ range which has lovely bright reds, purple and orange with attractive, dark-coloured foliage.

I wrote about Naomi Slade’s new book on dahlias here: https://bramblegarden.com/2018/06/24/dahlias-beautiful-varieties-for-home-and-garden/

How have your dahlias fared this year? Which method are you using to save them over the winter? Do you have any further tips to share?

Thanks for reading my blog, and listening in to BBC Radio Leicester for the gardening show on Saturdays at 11am. If you have any questions for either me or Josie, please leave a message here or get in touch with producer Dale. We are very pleased to still have a gardening programme when many other stations have now cancelled them.

I am @kgimson on twitter and karengimson1 on instagram.

11 thoughts on “Overwintering Dahlias – BBC Radio Leicester phone-in questions for Saturday, November 6 2021

    • I left mine in the ground two years ago and we had the wettest winter on record. Luckily most came through the winter as they were snug under large pieces of corrugated roofing. My mother leaves them in the ground; she has a lovely sheltered garden with well-drained soil. Makes it so much easier if you don’t have to dig them up and mess about with them. Have a great week, Derrick. Thanks for reading the blog.

      Liked by 1 person

  1. What would you advise for over-wintering Dahlias growing and flowering large flower pots Karen? We’re due storm force winds tonight so the Dahlias might be looking sorry for themselves tomorrow.

    An interesting article.

    X

    Liked by 1 person

    • Thank you. Very high winds here too. Strangely mild though. 12C tonight.
      I’ve got some in large pots too. You have two choices. You can either tip them out of the pots and wash off the compost and store them in a frost free place indoors. You can then use the pots for tulips. Or leave them in the pots, stop watering (they need a dormant period) lift the pot into a frost free place and leave there until spring. You’ll still need to cut stems back to 3” if you leave them in the pots. I’ve tried both. First method is the best. Second is ok unless the pot is full of snails and slugs, in which case they will munch the tubers. If there are any flowers left, just cut them and enjoy them indoors. They won’t produce any more buds now. Keep me posted. Karen x

      Like

  2. With our ground freezing solid, I have to dig my tubers. I clean them up, dry them for a day, then wrap them in newspaper and store in bags in the garage. If we have a deep freeze (which can happen in January) when even the garage drops below 35F, I put them in picnic coolers that add a bit more insulated protection.
    Worth the effort, esp. when I see the glory of them in late summer!
    Have a good week, Karen.

    Liked by 1 person

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