Lifting and storing Dahlias
With our climate getting steadily warmer some people will argue that it is possible to over-winter dahlias in the ground. While in a mild winter this may be the case, as a rule it is always safer to lift and store the tubers rather than take your chances with the elements.
Dahlias should be lifted once the first frosts have blackened the plants foliage but before the frost has had a chance to really penetrate the ground. To lift Dahlias you should first loosen the soil around the plant and then gently prise them upwards being very careful not to damage the tubers. A garden fork should be used for this job as there is less chance of damage to the roots. Once you have lifted the tubers, the old stems should be cut back to leave a stump about two inches long.
Now that you have lifted the tubers, the next step is to dry them for storage. The traditional and probably still the best way of drying dahlia tubers is to stand them upside down in your garage or garden shed so that the moisture drains easily from the hollow stems. A convenient way of doing this is to support the tubers on a wire mesh as this both holds the roots steady and allows plenty of air to circulate around them. After about ten days the tuber should be dry enough to store. Any surplus soil still on the tubers should be removed at this stage. The stem should then be trimmed back to leave a stump about an inch long. Finally trim off any old roots and any roots less than half an inch thick, leaving a small compact tuber that will be easy to store.
Store the tubers in well insulated wooden boxes with something like crumpled up newspaper or wood shavings packed lightly between them. Tomato boxes are ideal for storing tubers as they allow the air to circulate round the roots even when they are stacked on top of each other. Place these boxes in a frost free place such as a shed or garage. If you dont have a shed or a garage a spare bedroom will do provided it is not to warm as this will cause the roots dry out. Keep an eye to your tubers throughout the winter to ensure that they are all still sound.