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.
How can dahlia tubers be properly overwintered?
To overwinter dahlia tubers successfully, dig them up after the first frost, clean and dry them, and store them in a cool, dark place in a wooden box lined with newspaper and a peat-sand mixture.
The best time is after the first frost
Please be patient when overwintering dahlias until all flowers and leaves have completely wilted. This process should not be interrupted prematurely. All nutrients are transferred to the storage organs in the soil as energy reserves for the next season. At the same time, new buds form on the tubers. This rule of thumb has proven useful for determining appointments:
Winter dahlia tubers after the first frost when above-ground plant parts have died
There is no reason to worry if dahlias are surprised by the first light ground frosts, as long as the frost does not reach the tubers.
Overwintering dahlia tubers – step-by-step instructions
The soil should be as dry as possible right down to the tuber depth when you overwinter dahlias. Under this condition, the rootstocks can be lifted out of the ground with less effort. You should proceed correctly in this order:
Cut and dig up
- Cut the dahlia stems up to 10 cm above the ground
- Loosen rootstocks from all sides with a digging fork
- Lift tubers out of the ground with the garden fork
- Shake off the earth
- Cut off small roots and fibrous roots with secateurs
Mark dug-up dahlia tubers in the bed with a label on which the variety name and flower color are noted.
Sort out battered tubers
After digging, subject each rootstock to an initial critical inspection. Dispose of damaged rhizomes together with the dead plant stems in the compost. Only intact dahlia tubers without rotten spots are suitable for overwintering. At the latest in winter quarters, battered tubers spoil and, in the worst case, bring neighboring specimens to ruin.
Clean and dry dahlia tubers
Please clean dahlia tubers without water. A brush (€4.00 on Amazon) with hard bristles or a painter's puff is helpful. On this occasion, hold the hollow stem stubs upside down so that any remaining water drains away. 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. This is how dahlia tubers overwinter properly:
- Line the wooden box with newspaper
- Cover newspaper with a thin layer of peat-sand mixture or unfertilized coconut soil
- Place dahlia tubers side by side on the substrate without touching any points
- Cover the tubers completely with the substrate mix
Place the winterization box in the dark basement, a windowless garage or in a darkened garden shed with a frost monitor. From now on, visit the dormant dahlias every 14 days to remove rotting tubers.
Tip
Balcony gardening saves you the hassle of digging up and storing dahlia tubers. Dahlias can overwinter very well in pots. Simply cut off the dead stems to a hand's width above the substrate and put the pot in a dark, frost-free winter quarters.
