It is a well known fact that these quite picky individuals do not like to sit in water and, as our winters are becoming increasingly wet here in the UK, should we risk leaving these very gorgeous tubers in the ground to flower where they are for next year?
The Dahlia season will end with the first frosts...the frost will cause the foliage to die back in late Autumn/early winter depending on where you are. They will then need protecting over the winter...so you can either lift and store them or leave them where they are, in the ground (and cross your fingers!).
Leaving them in the ground:
They cannot literally just be left though, if the temperatures drop too much they will die off. Give them a little more protection by covering them with a course mulch, such as bark, but if you live in a particularly wet area you still run the risk of them rotting in the ground with the wet, even if they are protected from the cold.
If you have them in a relatively sheltered area though, this is perhaps the easiest option, just remember to mark where they are, as you will need to cut the foliage right back before winter and they will then sit below the soil line.
Lifting and storing:
This avoids the possibility of them rotting in the ground, however, you do need to store them properly. That means leaving them in a frost free, damp free place and ideally one where you can stop mice from making a meal of them!
When you lift them, shake off all of the soil and cut the foliage down to 5-15cm - then have a good look at them. Discard any that are rotten or damaged and leave them to dry out properly. Then put them in a crate or large flower pot with some dry compost or sawdust to regulate their temperature and moisture levels as much as possible.
Over winter...have a check on them and make sure they have no rot on them. However, it is also important that they don't dry out too much either...remember when I called them 'picky' earlier...well they are!
Spring:
Now is the time to plant out stored tubers or dig up and check, then replant ones that have stayed in the ground...ready for a glorious display later in the year. You see even if you leave them in the ground for ease...you will still need to check that they have over-wintered ok and not rotted away, unless you simply wait for them to flower...or not as the case may be!
We will be releasing our Mini Online Workshop on Dahlias in the next month or so for more detailed info on these majestic workhorses of the cutting patch, because, as 'picky' as they are...they are fabulous and will reward you with a huge number of blooms per plant if you treat them well.