Last weekend I was in the basement planting the last of my amaryllis and decided it was best to check the dahlia tubers. If you have tubers stored for next spring, now is a good time to see how they are doing.
The key to successfully overwintering dahlias is keeping the tubers properly hydrated. When spring comes, you want them to be as they were in the fall: as nice and firm as a freshly dug potato. The goal is to maintain a constant state. Too much moisture and the tubers will become mushy and rot. Too little and they shrivel like mummies. The best way to store them is in a box filled with peat, wood chips or sand.
I have stored the dahlia tubers in peat moss and it works great. But now I use a simple technique that works quite well and saves a lot of hassle.
Since I wait for spring to divide the tubers, they are kept as clumps, just as they were dug out of the earth. If the soil was wet when they were dug, I let them dry for about a week. Otherwise, each clump – with some dirt still attached – goes straight into a plastic grocery bag along with the label. This makes it easy to keep the varieties separate and not to confuse the names. I recently saw a creative solution for tracking which clump is which: tie a piece of duct tape around each clump and use a marker to write the name of the variety on the tape.
A clump of dahlia tubers stored in a plastic bag
Once the clumps are in their plastic bags, I nest 5 or 6 bags together (with the top open) in a layer on the bottom of a large black plastic garbage bag. The top of the garbage bag is collected freely but remains partially open for ventilation. This bag-in-bag technique is quick and works well, although I often lose a tuft or two. If you have prized varieties, I recommend continuing with peat moss. Remember that it is also important that dahlia tubers are kept cool, but not cold: 40-50 ° F is ideal.
When I checked the bags last weekend, most of the tubers looked great – like the clump shown at the top of this post. Some were a little shriveled, so I put a few handfuls of moist grow mix in those bags, and hopefully, they’ll rehydrate.
I didn’t save all the dahlias from last year. Only my favorites. The problem is that every year the list of favorites gets longer …