How to Dig Up and Store Your Dahlia Tubers
After a successful dahlia season you might be wondering how to care for these plants so that they'll deliver another glorious show next year. If your instincts tell you to remove those precious tubers before cold weather strikes and pamper them a bit so that they'll be strong and healthy before next year's planting season, then you're right. In order to repeat that stunning bloom performance, dahlia tubers should be stored indoors during the winter. Of course, there's more to this process than just some digging. Here, we share how to care for your hard-working tubers in between the seasons.
Who Should Dig Up Tubers?
Since dahlia tubers are temperature sensitive and only survive as far north as USDA zone 8, cold-climate gardeners are the ones who need to dig up the tubers and overwinter them. If you live in the mild temperature growing zones 8 to 10, you're fortunate that you can leave your dahlias in the ground and simply cut back the foliage. Then, patiently wait for them to grow again in spring.
When to Dig Up Tubers
You will notice after the first light frost that dahlia leaves turn brown, but don't worry because only the above-ground vegetation has been affected, and your tubers are still alive waiting for you to dig them up and store them away until next spring. Remember to label your plants with survey tape before removing them so you know what the varieties are.
How to Dig Up Tubers
You can dig up dahlia tubers with a garden fork or a regular shovel. Just be careful not to let the tool nick or pierce the easily damaged tubers—even minor punctures can introduce rot-inducing pathogens.
Begin by cutting back all the stems to within four inches of the ground, then loosen the soil around the tuber by pushing the tool of choice into the ground about a foot away from the plant. Carefully pry up the root ball, and with one hand on the fragile stem and the other under the clump of tubers, you can remove the mass from the hole. According to The American Dahlia Society, several methods of storing tubers can work equally as well "as long as the procedure keeps the tubers cool (above freezing but ideally below 50 degrees) and allows an exchange of moisture between the tubers and the storage medium. The containers, however, must retain the moisture in the storage medium. If the moisture escapes, the tubers tend to shrivel."
Some gardeners carefully dislodge most of the dirt from the tubers and then swish the tubers around in a bucket of water or hose them down to remove the dirt still clinging on. You can also take an extra step and sprinkle sulfur dust onto cleaned and dried tubers to prevent rot and deter fungus, then come spring plant them dust and all. Other gardeners recommend letting the tuber dirt clumps air dry for a day or two and then storing the entire root ball as it came out of the ground.
How to Pack Tubers
Packing can be done in various ways. One method is to hang the tubers upside down with twine, while some gardeners place the tubers in a mesh bag and allow them to cure outdoors for two weeks. This method only works if temperatures stay above freezing and there is no forecasted rain. If rain is forecasted, move the tubers indoors to a spot without direct sunlight. Some gardeners plant the root balls in large nursery pots or ventilated cardboard boxes partially filled with damp potting soil, peat moss, or sand. Another option is to store several clumps of tubers together in large black plastic trash bags with the top gathered so moisture stays in but there's still some air circulation.
Where to Store Tubers
Store the pots, boxes, or bags of tubers in a dark, cool, humid place where temperatures stay between 45 and 50 degrees. Remember: A frozen tuber is a dead tuber.
When to Check on Your Tubers
Periodically through the winter inspect your tubers for rot or if they're drying out. Carefully remove any mushy ones and reduce the moisture level if that happens. If the tubers appear dry or wrinkled give them a mist with water or add some damp growing mix to rehydrate them.