Want Dahlias to Return With More Blooms Next Year? Experts Reveal 5 Tuber Storage Mistakes to Avoid

A lot can potentially go wrong when you lift and store dahlias. The time from pulling tubers from the ground in the fall to planting them again in spring is littered with potential issues. It pays to know the dahlia storage mistakes to avoid so yours stay safe and avoid the dreaded rot.

Growing dahlias is hugely popular. It is no surprise, with a glorious range of blooms in a kaleidoscope of colors, shapes, and sizes to choose from. If you live in a climate with frosts, you need to lift and overwinter dahlia tubers indoors. This is when moisture, temperature, and proper care make the difference between healthy tubers and mushy ones.

I have grown, lifted, and stored dahlia tubers throughout my horticultural career, and have made blunders. To help you avoid falling foul of common dahlia storage mistakes, I chatted with experienced growers about how they store their tubers over winter. The process starts with chopping down the stems after the first frosts and lifting the tubers from the ground with a strong garden fork – I like this Berry & Bird stainless steel digging fork on Amazon.

Not Removing Excess Dirt

When you lift dahlia tubers from the soil, they usually come up with a lot of soil attached. It is important to remove all this excess soil before storage, though how thoroughly to do this varies among growers. What isn’t in doubt is the dangers of storing them with large clods of soil still attached.

Lindsey Chastain, an experienced gardener and homesteader, recommends that all loose soil be removed before you store the tubers. She adds: ‘If you have soil on your tubers before you store them, that can harbor disease organisms.

‘It can also hide soft spots or damage that cause tubers to go soft during storage, potentially infecting others in your collection.’

I have always used a wooden stick to dislodge packed soil from between the tubers and a soft brush to remove excess dirt. Some growers wash the tubers with a garden hose to rinse off the soil, but they then need to dry completely before storage.

Shelly Deaton owns EarthSpoke Farms, a dahlia farm that grows nearly 10,000 dahlia plants and over 400 cultivars, and she claims a thin layer of soil can form a protective barrier. ‘The soil acts as a protective layer around the tuber skin and can help keep tubers from drying out and shrivelling during storage,’ says Shelly.

The advice is to remove large clods and lumps of excess soil, but don’t necessarily feel the need to wash and scrub the tubers completely clean, as this brings extra pressure to dry them.

Not Drying Them

After cleaning excess dirt off the tubers, don’t just store them right away and think the job is done, especially if you have rinsed them clean.

Drying them is a crucial step in the process for all types of dahlias to ensure they come through winter unscathed. Skip this step, store them damp, and you’re guaranteed to be left with mushy dahlia tubers.

‘After rinsing, we make sure the tubers are dry before putting them into storage,’ says Shelly Deaton from EarthSpoke Farms. ‘Dahlia tubers already contain a lot of moisture, so putting them away wet can create condensation and encourage rot.’

To dry the dahlia tubers after cleaning and reduce your chances of mold, rot, and squishy tubers, place them in a dry, cool, well-ventilated spot for at least 48 hours and up to a week.

When they are ready, they should feel dry to the touch and firm. If any tubers feel soft at this stage, cut them off with pruning snips (available at Burpee) to preserve the rest.

Not Using Breathable Containers

Airflow is crucial to keeping tubers in good condition over winter, so use breathable containers rather than sealed or airtight containers. Breathable containers allow excess moisture to evaporate, while airtight ones trap moisture and humidity, creating condensation and ideal conditions for mold and rot.

Open crates or cardboard boxes with holes (you can easily poke some holes yourself) make perfect winter containers for dahlia tubers. Fill the containers with packing material that provides moisture and keeps the tubers insulated.

‘Vermiculite or dry wood shavings can help keep the moisture balanced, and both are pretty affordable online or at your local hardware or garden store,’ recommends Christina Stembel, the CEO at Farmgirl Flowers.

You can get a block of dried wood shavings at Ace Hardware, or a box of organic vermiculite at Amazon, to use for packing your tubers.

Shelly Deaton uses coconut coir at her dahlia farm. She claims: ‘We like coconut coir because it creates an environment that somewhat mimics being protected in soil while the tubers are dormant. Through a lot of trial and error, we've found this method works very well.’

You can get a block of organic coconut coir at Amazon

Not Finding the Right Temperature

Dahlia tubers are particular about how they like to spend winter. If it is too cold, they can freeze, causing damage and rot. If it is too warm, they may prematurely sprout. This makes finding the right spot crucial.

‘If you aim for between 40 and 50°F for most tubers, that's going to be a sweet spot,’ says Lindsey Chastain, adding that the location also must be cool and dark.

Shelly Deaton says she keeps her tubers ‘at approximately 40–45°F with high relative humidity around 90%’ over winter. Christina Stembel from Farmgirl Flowers is keeping hers at 42°F right now.

‘A breezeway, basement, or garage can work in most places as long as it doesn't get too cold,’ adds Christina. ‘You can get an electric space heater that will keep it at that temp for you as well, which is a good solution if you live in one of those places that dips well below that.’

Not Checking on Them

Don’t just pack your tubers into boxes, put them away in a garage or basement, and forget about them until spring. You might be in for a nasty surprise when you unpack them and end up with no dahlias to plant.

Many moisture, temperature, or pest-related problems can occur during storage. If one tuber starts to soften and rot, it can quickly infect others, potentially wiping out your entire collection if left until spring.

The experts recommend checking your stored tubers at least once a month. ‘If you catch a problem early – whether they're beginning to shrivel, showing too much moisture, or developing rot – you have a much better chance of correcting the storage conditions before you lose more tubers,’ says Shelly Deaton.

The dahlia farmer adds: ‘We recommend keeping a thermometer and humidity gauge wherever you're storing your tubers and checking them regularly throughout the winter.

‘An infrared thermometer can also be useful for checking individual storage containers because the temperature inside a container may be different from the ambient temperature of the room or cooler.’

Get an infrared thermometer gun at Amazon

What to Shop

You don’t always need to lift dahlia tubers. If you live in US hardiness zones 8+, you can leave them outdoors, mitigating the risk of making these dahlia storage mistakes.

Provided your soil drains well, you can leave dahlia tubers in the ground and mulch over them with a two-foot layer of straw (you can get a straw bale at The Home Depot) to protect them from low temperatures.

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