Dahlias are not hardy. The tubers must be dug up before winter. The right time is just as important as the expert approach. Read this guide on how to expertly overwinter dahlia tubers.
Dahlia tubers should be stored in a cool, dark place
The best time is after the first frost
Please be patient with the hibernation of dahlias until all the flowers and leaves have completely withered. This process should not be interrupted prematurely. All nutrients are transferred to the storage organs in the soil as an energy reserve for the next season. At the same time, new buds form on the tubers. This rule of thumb has proven itself for determining the date:
- Dahlia bulbs hibernate after the first frost, when parts of the plant above the ground have died
There is no cause for concern if dahlias are caught off guard by the first light ground frosts, provided the frost does not reach the tubers.
Overwintering dahlia tubers - step-by-step instructions
The soil should be as dry as possible down to the tuber depth if you dedicate yourself to overwintering dahlias. Under this condition, the rootstocks can be lifted out of the ground with less effort. The correct way to do this is in this order:
Cut and dig
- Cut the dahlia stems up to 10 cm above the ground
- Loosen rootstocks from all sides with a digging fork
- Lift the tubers out of the ground with a garden fork
- shake off earth
- Cut off small roots and fibrous roots with secateurs
Mark dug up dahlia tubers while they are still in the bed with a label stating the variety name and flower color.
Discard battered tubers
After digging up, subject each rootstock to a first critical examination. Dispose of damaged rootstocks in the compost together with the dead plant stems. Only intact dahlia tubers without rotten spots are suitable for overwintering. At the latest in the winter quarters, battered tubers spoil and, in the worst case, pull neighboring specimens into ruin.
Clean and dry dahlia bulbs
Please clean dahlia tubers without water. A brush with hard bristles or a painter's brush is helpful. On this occasion, hold the hollow stalks upside down so that any residual water can drain off. Then let the tubers dry for a few days in an airy, frost-free and rainproof place.
Store tubers in a cool, dark place
The dried dahlia tubers are now perfectly prepared for storage in the winter quarters. The location should be dark and cool with temperatures around 5° Celsius. How to overwinter dahlia tubers correctly:
- Line the wooden box with newspaper
- Cover newspaper with a thin layer of peat-sand mixture or unfertilized coconut soil
- Lay dahlia bulbs side by side on the substrate without touching
- Cover tubers completely with the substrate mix
Place the hibernation box in the dark basement, a windowless garage or in a darkened garden shed (€24.90) with a frost guard. From now on, visit the dormant dahlias every 14 days to remove rotting tubers.
tips
Balcony gardeners are spared the tedious task of digging up and storing dahlia tubers. Dahlias overwinter very well in pots. Simply cut off the dead stems to a hand's breadth above the substrate and put the pot in a dark, frost-free winter quarters.