How to Determine If Your Dahlia Tubers Are Dead

Dahlias are magnificent plants that bring a burst of color to your garden during late summer. However, if you live in a zone below zone 8, you’ll need to dig up and store your dahlia tubers over the winter to protect them from the cold. Unfortunately, if not stored properly, dahlia tubers can mold, rot, or dry out, resulting in dead plants come spring. Don’t worry, though! In this article, I’ll guide you through the process of identifying dead dahlia tubers, share tips on proper storage and care, and even teach you how to pre-sprout questionable tubers. Let’s get growing!

how to tell if dahlia tubers are dead

Storing Dahlia Tubers

The best time to dig up your dahlia tubers is after the first hard frost, when the flowers and foliage turn brown. Here’s how to prepare your dahlia tubers for storage:

Cut back the stems and dig up the tubers

Start by using a clean pair of pruning shears to trim the stems back a few inches above the ground. Next, carefully dig around the plant, making sure not to damage the tubers. Gently lift the tubers from the ground using a garden fork or spade.

cutting dahlia stems before digging up tubers
dug up dahlia tuber clump

Label the tubers

If you have multiple dahlia varieties, be sure to label each tuber clump as you dig it up. This will make it easier to identify them in the spring. I recommend tying flagging tape around each stem with the variety name and bloom color written on it.

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dahlia tuber clump with variety labeled with flagging tape tied around stem

Clean the tubers and let them dry

Shake off any excess soil from the tubers and use a soft brush to remove any remaining dirt. You don’t need to remove every speck of dirt, but make sure there are no large clumps that can hold moisture. Avoid using water, as it can cause the tubers to rot during storage. Place the tubers in a well-ventilated area and let them dry for a few days to prevent mold growth. I usually leave mine in a shady spot on our deck where they can get air circulation on all sides without shriveling up in the sun.

cleaned off dahlia tuber clump

Store the tubers

Place the tubers in a box or container filled with slightly moistened peat moss, vermiculite, or perlite. Make sure the tubers do not touch each other to prevent rot. Personally, I like to use a large, clean grow bag filled with vermiculite, which I reuse year after year. The fabric allows for air circulation, preventing mold, and the vermiculite keeps the tubers from drying out. Just ensure that all the tubers are below the surface of the vermiculite, with only a few stems sticking out for easy access.

dahlia tubers stored in vermiculite

Store the container in a cool, dark place with a temperature between 40-50°F (4-10°C). Avoid putting them in an unheated garage if there’s a risk of freezing temperatures. Throughout the winter, periodically check on the tubers by using a soil thermometer. By following these steps, you’ll give your dahlia tubers the best chance of surviving the winter and thriving in your garden come spring.

Signs of Dead Dahlia Tubers

After storing your dahlia tubers over the winter, it’s essential to check their condition before planting them in the spring. Here are some signs to help you determine if your dahlia tubers are dead:

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Healthy tubers should feel firm to the touch. If a tuber feels soft or squishy, it’s likely rotting and should be discarded. If it’s emitting a foul odor, it’s definitely dead!


Inspect the tubers for any signs of mold or fungus. Mold usually appears as a fuzzy or powdery white, green, or black growth on the surface of the tuber. If mold covers the entire tuber, it’s probably dead and should be thrown away. However, if there’s only a small amount of mold, you may be able to save the tuber by cutting away the affected area and treating it with a fungicide or sprinkling it with cinnamon, which acts as a natural fungicide.


If a tuber appears shriveled or dried out, it may be dead. Healthy tubers should be plump with a smooth surface. However, a dried out tuber may still have some life left in it, so you can try pre-sprouting it using the process outlined below.

shriveled dahlia tuber

Pre-sprouting Questionable Dahlia Tubers

If you’re unsure whether a tuber is alive or dead, you can try pre-sprouting it before planting. This process is simple and doesn’t require much space. It guarantees that you’re only planting healthy tubers that will bloom beautifully in your garden.

Place the questionable tuber in a quart-sized plastic sandwich bag with some potting soil and lightly mist it with water. Leave the bag open and place it in a warm, sunny location or under grow lights. After a week or two, check on the tuber. If you see white roots through the clear bag or sprouts emerging from the top, it’s alive and ready for planting!

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sprout emerging from shriveled dahlia tuber

If the tuber starts to mold or if you don’t see any roots or sprouts after a few weeks, you can safely discard the bag and the dead tuber. I personally use this pre-sprouting method for all my dahlia tubers after dividing them to ensure there’s a viable eye on each one. It takes up less space compared to potting them up individually, and it’s easy to observe root development through the bag. You can even leave them in their bags for a few extra weeks if your weather isn’t warm enough to plant outside yet. Just make sure not to overwater them and accidentally cause the tubers to rot.

presprouting dahlia tuber in plastic bag

When it’s time to plant the tubers outside, rip the bag down the side instead of pulling it up through the top. You don’t want to accidentally damage the sprout or disrupt the roots! Once the tubers have developed at least three sets of leaves, it’s time to pinch your dahlias. This will promote more flowers from a single tuber and create sturdier plants.

If you’re still waiting for your dahlia to bloom, check out this article on 7 reasons why your dahlias aren’t blooming. It will help ensure you did everything right!

I hope this article has answered your questions about how to tell if your dahlia tubers are dead or not! In general, dahlias are pretty resilient plants, so don’t lose hope even if your tubers look rather sad. Just place them in a bag of soil and see how they fare! For more information on a wide range of topics, visit 5 WS.

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