These may include: Stem rot – Stem rot occurs when dahlias are growing in heavy, poorly drained, wet soil. As you can read from these dahlia care instructions, removing your tubers, treating them with a fungicide, and storing them appropriately will go a long way toward preventing this problem, which flourishes in cool, wet soil. Also true of any pruning tools.I hope this is helpful for you. Dahlias are a breeder and collector’s dream. Some gardeners advise dusting the tubers with a fungicide before packing. Step 2: My first split will more or less break the clump in two so I can split it down further. Dahlia tubers are not terribly winter hardy and will rot in the ground in many regions. By: Bonnie L. Grant, Certified Urban Agriculturist. Dahlia tuber rot is caused by a specific fungus – Botrytis cinerea. Infected dahlia tubers will break down, soften and ultimately rot. )The other major thing you need to change is putting plastic over your garden. Tuber Rot on a Dahlia Causes. Taking a few samples for review, a nursery person suggested it was Iris soft rot, caused by bacteria. Most of the tubers are showing growth now, but I started digging around those that had not appeared. Thanks much! In temperate zones where freezes are not sustained, you can store them in a basement or garage in a paper bag. It is best to dig them up and store them indoors for the cold season and then reinstall them in spring. I'd keep turning it for a few weeks before planting anything else. This helps to cure them and to prevent rot during storage. They split in freezing temperatures and mold in soggy soil. Choose a location – either indoors or out – that won’t dip below freezing, has good air circulation, and indirect sunlight. It is a weak pathogen requiring some kind of predisposing factor that stresses or injures the plant before it can become established, thus it is often a secondary invader. The plants are perennials in USDA plant hardiness zones 6 to 7 but will succumb in the ground in lower zones. Gardeners differ on the best way to pack overwintering dahlia tubers. If it doesn't exist in the forest, it doesn't belong in your yard! Plant them out again after all danger of frost has passed and enjoy their brilliant tones and flashy forms. When you put down plastic, you not only keep the soil from getting needed winter moisture, but you cut down/out the oxygen in the soil and make it a paradise for fungi that need cool, damp environments. If possible, dry your dahlia tubers for several weeks before putting them away in storage for the winter. You must destroy the plant, as there is no cure. Drying is important to saving dahlias over winter and preventing them from rotting. The discoloration probably indicates crown rot, and the tuber is unlikely to keep. It is best to dig them up and store them indoors for the cold season and then reinstall them in spring. Environmental changes in the storage location, such as increased humidity or fluctuating temperatures, can still damage overwintering dahlia tubers. Cut off the foliage and carefully dig out the tubers. After cutting divisions, use a hose or indoor laundry tub (in cold weather) to wash the tubers again and remove any dirt missed when first washing the clump. 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Ask an Expert is made up of groups and individual experts. Can you recommend any further resources to help me learn more? As you can read from these dahlia care instructions, removing your tubers, treating them with a fungicide, and storing them appropriately will go a long way toward preventing this problem, which flourishes in cool, wet soil. (Don't compost! When to Dig Up Dahlia Tubers Mother Nature will alert you when it's time to dig up your dahlia tubers. Look for a white ring in the... Mosaic virus – Mosaic virus dwarfs plants and distorts leaves. After rewashing, cut the end of the tuber. The dahlias were cut back to the ground in November, covered with black plastic, and a leaf mulch layer (about 3 inches) placed on top. Wait until the foliage has turned yellow before digging up the tubers. It will store starches in the tuber which will fuel initial sprouting in summer. You probably don't need to dig all that soil out, because if it is turned (gently!) Tuber rot in dahlias is caused by a species of fungus, Fusarium, commonly found in soil. Assuming the problem has correctly been identified (and I could provide a sample if needed), what steps should be taken now? I found mushy, bad smelling tubers with lots of earth worms. I have googled for some more information and would greatly appreciate input from a Master Gardener. They come in such a wide variety of sizes and colors that there is sure to be a form for any gardener. Surrounding tubers (about 24" apart) are intact and sending up lots of growth. Dahlia tubers are not terribly winter hardy and will rot in the ground in many regions. In tubers it causes brown rings and most importantly results in tuber rot during storage. There are several ways of storing dahlia tubers for winter. Step 1: Clean up all the roots at the end of the tubers and any tubers with broken necks. Here is another WSU Extension article on the same topic. Of course, if your tubers are stored appropriately elsewhere, they won't mind.Covering the soil with the leaves is fine. What preventative and proactive steps can I take to prevent this problem? The mushy tubers have been thrown out, but should I also remove the soil that surrounded the tuber area? At this point, only the aboveground vegetation has perished. Whatever method of dahlia storage you choose, you will need to check the tubers occasionally to ensure they are not rotting. They split in freezing temperatures and mold in soggy soil. If possible, hang them upside down when drying them so that moisture can leach out of them. Once the skin is wrinkled, the tubers should be dry enough. In March the coverings were removed, and I waited evidence of new growth. Tips for Saving Dahlias. Thank you for your question, Cathryn. You may also try storing them in a heavy plastic bag with packing material or even a Styrofoam ice chest. Good luck! However, they do need to keep slightly moist on the interior to keep the embryo alive.