Unearthing your Dahlia Tubers
When to unearth your dahlia tubers
It is a nice weekend, the last in September or maybe first in October and there has not been a serious frost yet. This is the ideal time to work outside and preapare your garden for the winter, but please don't touch your dahlia tubers!
Dahlia tubers develop and form themselves mostly between late August and mid October. Before unearthing them, it is necessary to give them the time to grow and store as much energy as possible in order to survive the winter. At the farm we have discovered that unearthing them AFTER a frost gave us much more vigorous bulbs. We did a test and unearthed two groups: group A (october 5-9) and group B (october 20-29) with a frost occuring on the night of october16-17. Our group B tubers, the following spring, produced more vigorous tubers, quicker sprouts/shoots and began to flower earlier than group A.
A good indicator that a dahlia tuber is ready for unearthing is the plant showing darker stems and leaves due to a frost. A frost of -2 °C and below usually does the trick. If your tubers have formed deeply enough, the frost should pose no danger to them for a while if left in the ground (ie: until the weekend).
How to unearth your dahlia tubers
After a good frost, cut the stems at about 15cm (6'') from the ground. This part of the stem will serve as a handle during the process. Then, with a shovel, cut an incision at least 12" away from the stem - forming a circle around your plant. The incision should be deep enough to sever any secondary roots while not damaging the tuber itself. Once you've formed a deep circle with the incision made by shovel, use the latter to gently lift out the tuber and soil clump, simultaneously pulling on the stem you have left for yourself.