So, your dahlias are dug, divided, cleaned, and have dried for a few days. Guess who’s ready for winter storage? Yes!
How to pack and overwinter is your next and final task. You have a few choices. I have tried three separate methods over the years. One method is to put your tubers in peat moss, which is slightly damp. A fresh bag of peat moss is usually a good dampness for storage. You could add a bit of water and moisten evenly with the goal of having the peat moss slightly more moist, but not dry and not wet. Too wet and you risk having your tubers rot. Too dry and the tubers will dry and shrivel, and will be unable to push out new growth in the spring.
A second choice of storage method is to put your tubers in a container that has moistened wood pet shavings. I do not use cedar shavings. I use the light colored wood shavings instead - aspen is common. As with peat moss, the shavings should be moistened so the tubers will not dry out over winter.
With either peat moss or pet shavings, I put my tubers in cardboard boxes. I use the “banker’s boxes” because it is easy for me to lift a top off and check tubers every so often in the winter to determine if any are rotting or are too dry. If they happen to be dry, or the peat moss or shavings have dried, I spritz using a spray bottle of water. Most growers advise against using plastic bins so the tubers can “breath” and the risk of rotting is reduced. I do know a number of gardeners and a few growers who have used plastic bins or garbage bags without problem. Hmmm… sorry to be complicating your thinking.
The packing method I use for storing in cardboard boxes is to first place a layer of either peat moss or shavings on the bottom of the box. Next I put in some tubers. I then scatter peat moss or shavings over and around the tubers. I keep going in this manner until the box is almost filled. I make sure to add peat moss or shavings on the very top to keep all tubers covered. If any are not covered they risk drying out.
Because I store a lot of tubers, I do not label each tuber. I simply put all of one kind in a box. In some cases, I put several kinds in one box, but I separate them with sheets of newsprint paper. I use the kind you can find for moving rather than inked newsprint. Just my personal preference. I make sure to use more than a single sheet and to be very careful unpacking in the spring because the paper can tear easily when it is moistened. Since I do not label each tuber it is essential that I do not let different varieties mix if I want to keep track of what’s what.
Since I am guessing you might have several varieties of tubers, it is a good idea to label them before you store them. How to do this? A permanent marker works quite well. Simple write the name directly on the tuber. You are done!
As you might recall, I alluded to three methods of storing dahlia tubers. The third one is to wrap your tubers in a clear cling wrap - what you use to wrap food. Simply tear off a piece of cling wrap, put your tuber in it, and wrap it up tightly. This method has worked well for me in keeping moisture in and also is a space saver compared to storing tubers in peat moss or clear pet shavings. You can simply put the wrapped tubers into a box and you are done. When I am storing in this method I first wrap individual tubers and then bundle a number of individually wrapped tubers of the same variety together with additional cling wrap. I then put a piece of blue painter’s tape around the bundle to keep everything together. Permanent marker works great on the blue tape for labeling purposes.
To overwinter well, dahlias should be kept in a cool, dark location. The cardboard box helps keep them in the dark. Ideally, storage temperature should be between 36 degrees and 45 degrees. Basically, don’t let them freeze, but don’t let them get above 50 degrees or they will break dormancy and shoots will commence growth. I have the benefit of being able to store in my floral cooler. From home gardeners I have heard storage success stories involving the garage, basement, crawl space, steps leading to the attic and steps leading from the basement to the outdoors. A finished part of a basement is usually too warm. Garages will occasionally freeze. To combat freezing temperatures in the garage, some have had success by putting their tubers in a cooler or putting insulating material around their box of tubers. Here’s a trick for checking temperature where freezing is possible: place a bottle with a small amount of water in it in the location to be checked. If the water starts to freeze, your dahlias need protection - either move to a slightly warmer location for the duration of the cold spell, or insulate a bit.
So, that’s it! Your dahlias can get ready for a nap. You can get going on those seed orders, and wonderful winter moments perusing plant catalogs and websites. Great job!