How To Tell If Dahlia Tubers Are Dead?

By Paul Smart •  Updated: 10/04/21 •  6 min read

How To Tell If Dahlia Tubers Are Dead? Dahlias are one of the most beautiful flowers to grow in the garden. However, to ensure that the flowers appear year after year it is important to lift and store the tubers over the winter months. However, many of the tubers that have been stored in winter don’t look very good. How do you tell if the tuber is still alive?

Telling whether a dahlia tuber is dead can be difficult, even for the most experienced gardeners. In short, if the dahlia retains plump moist flesh somewhere in the tuber it will resprout in spring. The trouble is that tubers that appear to be completely dried out sometimes contain a small amount of viable flesh in them that allows them to reshoot. As such you need to take the approach that the Dahlia tuber is dead unless proven otherwise.

The image below shows a picture of a Dahlia bulb that definitely is not looking too good but it is one that would almost certainly be still alive as there is still quite a bit of body within the tuber which suggests that is not completely dried out.

For those tubers where you have serious doubt about their viability advisable to plant them into a pot and wait for signs of life. I can tell you from first-hand experience that dahlias are real survivors, as I have had shoots appear from the compost heap when I had long since given up on them.

How To Stop Dahlia Tubers From Drying Out In Storage

There are several ways that are recommended for storing dahlia tubers in winter. One of the most common ways that is recommended is to simply clean and dry the tubers and then leave them in a box after they have been lifted. However, the disadvantage of this method is that its success is highly dependent upon the storage conditions.

Low humidity environments can result in the tubers losing moisture too rapidly and being completely dried out. The method I prefer to use is to store the tubers in a medium like peat moss, slightly damp sand, or sawdust. This allows you to control the environmental conditions much more easily. However, it is important to note that the medium that you store the plant in needs to be only slightly moist as there is a risk that the tubers will rot if the medium is too wet.

To reduce the chances of this occurring some gardeners advise dusting the tubers with a fungicide before packing them, however, I have personally not found that to be necessary, however, it will certainly reduce the chances of bacterial and fungal attack.

When Should You Dig Up Dahlias

Dahlia tubers only need to be removed from the ground if you live in hardiness zones 6 or lower due to the low temperature which can kill the plants. In these colder zones dahlias need to be treated as annuals. The other reason that it may be necessary to dig up dahlias is if you live in an area that is extremely wet during winter, as there is potential for the plants to rot in the ground.

In terms of timing, the best time to dig up the tubers is in mid-autumn when the foliage is beginning to die back. This is usually around a week or two after the first frost, but prior to the point where there is significant snowfall or the ground becomes frozen as the will definitely result in the tubers becoming damaged.

When removing the tubers it is best to remove them as an entire clump carefully. To reduce the chances of damaging the tubers it is best to start digging around 1 and half feet away from the foliage using a fork rather than a spade or a shovel. The reason for this is that if you accidentally hit a tuber with a fork which will only spear the odd tuber whereas a shovel will most likely cut it in half.

Gradually make a trench around the outside of the tubers and gently lift them and try to remove the clump in one piece as this will allow you to make the most of tubers in terms of division.

Preparing Tubers For Storage

Once the tubers are removed from the ground the first step is to wash them thoroughly to ensure that all the soil is removed, the tubers will then need to be dried. At this stage, they can either be packed away as a whole mass or they can be divided first.

My personal preference is to divide them as it makes them easier to pack into the storage medium, additionally, it reduces the chance of there being air pockets in the medium which will reduce the chances of them drying out.

To divide the tubers they need to be separated at the central point apex of the clump where the end of the tuber is narrower. At this end of the tuber, an eye or growth point will form. To ensure that each divided tuber creates a new plant at least one eye needs to be included on the cutting.

The eye is a circular formation that can be seen on the surface of the tuber, the thumbnail image for the video below from Garden time shows the gardener pointing to the eye in the center of the clump of tubers. To see a demonstration of how to separate the individual tubers watch the short video below.

Storage Of The Tubers

Once the tubers have been separated the best way to pack dahlia tubers away is to use store them in a plastic container or a Styrofoam ice chest. Start by laying a 2-inch layer of peat moss or sand in the base of the container. Place the individual tubers into the sand ensuring that they do not come into contact with each other.

Separating the individual tubers ensures that if one tuber rots they are not all affected. Once the tubers are in position place another layer, 1 to 2-inches thick of sand on the tubers. Additional, layers may then be added depending upon the depth of the container being used.

Once the container is full it should be placed in a cool dark location that doesn’t allow the container to freeze. The ideal temperature is 40 to 45°F (4 to 7°C.). In areas that have moderate temperatures, places like a basement or garage are ideal.

Paul Smart