Overwintering Dahlias

The nights are drawing in, leaves have started to litter the lawn and the heating thermostat has kicked in at home… Autumn has arrived and it’s time to start thinking about preparing my garden for the winter.

Continuing from my last couple of posts about dahlias, this week I’m going to write about over-wintering dahlia tubers. The dahlia was originally discovered in Mexico and although it has given centuries of enjoyment to British gardeners it has yet to get used to our colder northern hemisphere winters!

Dahlias should continue flowering until the first light frost which will kill off the foliage. Once the foliage has blackened you can remove it and dig up your dahlia tubers. If you have a dahlia bed with lots of tubers this can be a mucky and difficult job – a useful tip for next year from my friend Boris Legarni is to lay a strong mesh underneath your dahlia tubers – this technique can be applied to all bulbs and tubers which need sheltering over winter and makes lifting the tubers much easier next autumn.

Storing Dahlia Tubers Over Winter

Once you have dug up your tubers spread them out upside down (so that they don’t get any ideas about throwing up new shoots!) in a greenhouse or porch to dry them out. It is important to ensure that they are completely dry before putting them away for the winter so that they won’t rot. Any dry, cold dark place can be used to store them as long as it will not get below freezing – a cellar is ideal. More particular gardeners actually store their dahlia tubers in a box of dry sand in the greenhouse or cellar – this mitigates the risk of wetness and rot and also helps to keep them snug over the cold winter months.

When digging up you dahlia tubers you may find that the palm sized tuber you planted last spring has doubled or tripled in size. You can actually divide the tuber using a sharp knife and ensuring that each section has a bud eye from which the new plant will sprout come spring.

It is very important not to plant out your dormant dahlia tubers until you are sure that the final frost has been and gone. This year I lost a few tubers because I planted them out at the end of March and was surprised by the late April frosts.

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