But in the north (USDA Zones 7 and down) they cannot survive to thrive through the winter. As the temperatures plummet, the careful composition of the dahlia tubers can be destroyed and rot. Therefore, to enjoy the splendors of these blooms, every Autumn, they need to be dug out. They work precisely opposite of the Spring bulbs we plant every year to overwinter.
Digging Up Dahlia Tubers
We’ll preface by saying that you may come across what feels like differing accounts and advice on how to do this successfully. To that we say that there are different ways to achieve the same goal. And that one method may be preferred and feel the easiest to you but can differ from your neighbor. It’s one of the quiet joys of gardening: you get to find out as you go. The main goal is to have your dahlia tubers safe during the winter.
Wait for the First Frost
This may seem counterproductive as we aiming to protect the tubers from the cold. But often the first frost coincides with around 120-140 days of growing (about 3 to 4 and half months) which is ideal for the tubers. You can certainly dig them up prior to that, but many professional flower growers call this even ‘frostman’. Within 24 hours all your foliage will turn black.
Cutting (and Waiting)
Some say to wait to cut down your foliage once it’s gone black. The idea that the energy from the plant will be sent into the tubers. It’s not however, as romantic as that–yes, a portion of the starches and nutrients are sent down or ‘dumped’ into the tubers, but nothing significant. So once blackened, cut to the soil*. The waiting references the tubers in the ground. If time and weather permit, in that it’s not going to be actively snowing just after that first frost, wait 1-2 weeks before digging up the dahlia tubers. Similar to curing seed potatoes, keeping the tubers for that week or so allows to them to thicken their skin and make their ‘eyes’ more visible (more on that soon) increasing successful storing.
*Some growers will leave a few inches above the ground to create a handle when digging. While helpful in the next step, if the stem gets too wet it can cause problems underground. In your first year, try both and see which you feel more comfortable with and see higher success.
The Art of Digging (and Drying)
We call it an art, because this step requires care and precision. Tubers are extremely fragile. Loosen the soil around the tubers, and gently lift them out of the ground. Avoid harsh yanking or pulling. Once out of the ground, remove any broken tubers, cut down root hairs and remove excess dirt. From here set into crates, screens or wooden boxes until their are dry to the touch. Keep them in an area that is cool but where they will not freeze.
Dividing and Storing
Dividing can occur in either the Spring or the Fall, if the latter, you’ll have an easier time storing them but should check on them frequently through the winter. If the former you’ll just need a larger over-winter storage solution. Divide your clumps into individual tubers. Look for small green/brown ‘eyes’ that indicate viability. Only keep those. Once divided we love using large tupperwares filled with vermiculite, place them in ensuring no two tubers are touching. Keep them in a fridge or cold room (about 4-6C and 60-80% humidity). Through the winter, check for anything mushy at least once a month and remove accordingly.
Proper overwintering will lead to years and years of dahlia enjoyment. We wish you all the luck in digging up your dahlia tubers. For more things home and garden, keep reading the Wild Blog. P.s., if you don’t already, be sure to follow us on Pinterest and Instagram.