There are no hardy dahlias for the garden. Only in Mexico, the homeland of the Georgian, is a variety of winter-hardy dahlia known, a natural dahlia that can cope well with sub-zero temperatures. The cultivations in local gardens do not survive a cold winter outdoors.
Are dahlias hardy?
Unfortunately, hardy dahlias for the garden are not available in our latitudes. Most dahlia varieties do not survive cold winters outdoors and must therefore be dug up in autumn and overwintered frost-free.
Don’t plant dahlias until spring
The young shoots of the dahlia cannot tolerate frost at all. That's why you can only plant early dahlias outside after the Ice Saints.
You can plant the tubers in the ground at the end of April, provided the soil has warmed to at least ten degrees.
Overwintering non-hardy dahlias
Since dahlias are not winter-hardy, you need to protect the tubers from sub-zero temperatures. There are several ways to do this:
- Overwinter tubers in the cellar
- Leave tubers in the pot
- Store tubers without a cellar
- Protect tubers outside from frost
You will have the fewest losses if you take the tubers out of the bed or pot in autumn, let them dry and then store them in a wooden box in the basement. Alternatively, a plastic bag with some soil and lots of small holes will also work. Every now and then the dahlia bulbs need to be slightly moistened.
Particularly beautiful dahlia varieties that you are very attached to should always be kept in the cellar over the winter. All other methods are not so reliable. Many dahlia tubers do not survive these forms of overwintering.
Do non-hardy dahlias overwinter without a cellar?
If you don't have a basement, you can try overwintering the dahlia tubers in the utility room or a frost-free garage.
It is important that the room is not too humid, not too warm and not too bright.
Overwintering dahlias in a pot
If you want to overwinter your dahlias in pots, cut down all the stems after the first frost at the latest so that only a few centimeters remain above the ground.
Place the pots in a cool but frost-free place where it is as dark as possible. As soon as the temperatures rise above ten degrees, the tubers begin to sprout.
Overwintering dahlias outside
Some gardeners report overwintering non-hardy dahlias outside. However, there is a great risk that the tubers will not survive this.
If you want to give it a try, winterize the dahlias as follows:
- Cut down stems
- Apply a thick layer of leaves and soil
- Additionally cover the planting site with bubble wrap
- Remove the winter cover in spring
Overwintering outside is best if your dahlias grow close to the house or in a very temperate climate. In mild winters, most georgines survive - if they don't rot due to too much moisture or are eaten by voles.
Tips & Tricks
Before you get the georgines out of the ground, cut the stems down to ten centimeters. The root collar on the tubers must never be completely removed. This is where the new shoots develop that will produce flowers next year.
