7 Dahlia Tuber Storage Problems to Avoid This Year

There is an art to storing dahlia tubers that keeps them healthy and ready to spring back into action when the weather warms up. Join gardening expert Melissa Strauss to uncover some mistakes you can avoid to keep your bulbs fresh and maintain their dormancy until spring.

Dahlia tubers stored in a black plastic container in an autumn garden, prepared for overwintering.

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Growing dahlias can be a wonderfully fulfilling adventure. Their large, flamboyant, and varied blooms make gorgeous cut flowers and make a statement in the garden. Sadly, if you live north of Zone 8, they can be high maintenance during the colder months. 

If you live in a cool climate, you can successfully grow these plants, but the roots won’t survive the winter if you leave them in the ground. You’ll need to dig them up and store them if you want to save them for the next year. Those tubers can be pricey, so saving them saves you. 

Storing dahlia tubers isn’t difficult. However, there are some specific steps and conditions that will make storage more successful. Preparing and storing your dahlia bulbs correctly just takes a bit of foresight. Here are some mistakes to avoid when bringing those tubers in for the winter.

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Not Waiting Until the Foliage Dies Back

Close-up of a gardener using pruning shears to trim the tall stems of a plant, separating them from the bulbous roots with pointed tips and a slightly wrinkled surface, in a picturesque garden.
Cut back after frost to encourage stronger roots for dormancy.

If you want to start off on the right foot, allow your plants to die back after the first frost. Dahlias are sensitive to frost, and the first one will kill most, if not all, of the foliage. While this step is not a make-or-break situation, it will encourage stronger tubers that are more well-equipped for storage. 

After that first killing frost, the foliage will turn brown and then black as it dies. Once it turns, go out with a pair of loppers or shears and cut the stems down to about four to six inches tall. 

Cutting off the foliage accomplishes an important objective. It signals to the plant that it is time to prepare for dormancy. Even in warm climates, these plants go dormant in cold weather. This will encourage your tubers to set eyes for next year’s growth, and they will begin to cure a bit. 

After you cut them, wait a week or two for this to happen. Try to be patient, they will be just fine as long as the ground doesn’t freeze. When you’re ready, use a garden form to gently loosen the ground around them. Use your hands to lift them, to preserve as much as possible and not scrape up the outside of the bulbs. 

Not Curing Your Tubers

Close-up of clean, plump, finger-like tubers drying in a black plastic container under full sun in an autumn garden.
Clean and cure bulbs in a cool, dry space to prevent mold.

Once you’ve got them out of the ground, it’s important to cure your bulbs properly before storing them. There is an art to this, as you don’t want to dry them out completely, but not enough, and you’ll end up with a mold issue. 

Before you cure them, your bulbs should be thoroughly cleaned. Don’t leave soil on them that could contain fungus or pathogens. Also, make sure that you remove any signs of fungus. Some portions of the roots may be rotting from a rainy summer. Trim those off and dispose of them. 

To cure your clean, dry bulbs, lay them on a tray in a single layer so that air can circulate around them. Set the tray in a cool, dry, dark space for about anywhere between a few days to a few weeks, depending on where you live. If you live in a humid climate, give them more time to cure. 

The curing space should have good ventilation, but don’t use a dehumidifier or fan. You don’t want to suck all the moisture out. You just want the outside to be dry and toughen up. Don’t allow them to dry to the point that they become shriveled, or you will reduce the chances of them coming back. 

Wrong Storage Container

Black plastic boxes filled with fleshy, elongated tubers that have a brown color, rough texture, and narrow necks connecting to a central stem.
Proper preparation and airflow are essential for bulb preservation.

The way you prepare your bulbs for storage is of great importance. There is not one exact way that is better than all others. However, some generally accepted methods are superior in preventing rot. 

The first mistake you can make in your storage containment is to deprive them of all moisture. You must strike a balance between providing just enough moisture to keep them hydrated and not enough to grow mold. Air circulation is important for this reason. 

Choose a container that doesn’t hold water. Something like a mesh back or cardboard box works well. I like shallow cardboard boxes that allow for only one layer, and then you can stack them to save space. 

Next is the packing material. Surround your tubers with a loose, airy material that will hold some moisture but allow air to circulate. Vermiculite or wood shavings are great for this purpose. Moisten your packing material lightly before tucking the boxes away for winter. 

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Too Much Heat

A large pink plastic container filled with swollen, root-like structures that have a firm, slightly curved shape and are covered in a light, earthy skin.
Keep bulbs dormant by storing them at 40-50°F (4-10°C).

Storing your tubers at the right temperature is another important factor in success. You won’t want to just tuck these into a closet or corner of the house. To store them effectively, you want your bulbs to remain dormant. If they come out of dormancy, they will sprout. 

Dahlias go dormant at temperatures between 40 and 50°F (4-10°C). It’s tough to achieve this inside the home because most folks are a bit chilly at those temperatures! A garage is typically a good place to store bulbs for the winter. 

As long as your garage doesn’t drop below freezing, this is my recommendation. Place your boxes against the wall that connects to the house, as this will be the warmest spot in the garage. 

Too Much or Not Enough Moisture

Plump, sausage-shaped tubers with a thin, dry outer layer are clustered together in a dense bundle.
Keep bulbs lightly moist to ensure healthy spring growth.

These next two issues may seem contradictory, but hear me out. Maintaining the right moisture level around your tubers is important. If your bulbs come in contact with excessive moisture over their storage period, they are open to fungal diseases. If they dry out completely, they are unlikely to survive. 

You want to mimic the natural dormant conditions they would undergo in the ground. There should be some moisture around them, but only enough to avoid dehydration. The material around your tubers should stay lightly moist, not wet. 

If you can maintain this balance throughout the storage period, you will have the healthiest bulbs in spring. A spray bottle is a valuable tool for achieving this light moisture level. Misting the packing material will help keep just a bit of moisture present. 

Not Enough Air Circulation

Wooden boxes in a barn filled with thick, tuberous roots that are slightly tapered at the ends, featuring pale, fibrous skin and irregular shapes.
Ensure proper air circulation to maintain moisture balance.

To strike the right moisture balance, it’s equally important to ensure adequate air circulation. This is where packing material comes into the equation. However, the container and storage space also matter. 

Some gardeners store their tubers in plastic bags, and I’m not going to say that this is wrong. I’m also not recommending it. Here’s why: plastic is not conducive to proper air movement. A bag made of fine mesh or even an old pair of stockings would be better if you want to hang your storage container. 

I prefer a paper bag or cardboard box because they are lightly absorbent. They won’t hold moisture to the point that it causes decay. Ensure your packing material will also hold just a bit of moisture and won’t break down and rot. Soil is not a great packing material for this reason.

Finally, your storage space should have some air circulation. This is especially true if you live in a humid climate. A damp garage with no ventilation is not a good spot. Make sure the space you choose is cool and dry

Not Checking In

Close-up of a male gardener carrying a black plastic box filled with clusters of thick, oblong tubers with smooth, light brown skin and slightly curved forms connected by a central stem.
Regularly check for moisture balance and signs of mold.

It would be nice if proper storage was fail-proof, but it’s simply not. Sometimes, despite our best efforts, we end up with moldy roots. This is why my final bit of advice is to check up on your bulbs from time to time. I recommend this with any bulbs that you store for the winter (or the summer, as the case may be.)

You don’t need to check in on them daily or even weekly. Once a month should be plenty. When you check up on them, you’re looking for signs of moisture imbalance. If your bulbs look dry and the skin is wrinkling, you need to mist that packing material before you pack them away again. 

Conversely, you want to make sure that if some mold does form, you’re getting it out of there as soon as possible. Look over all of your tubers and inspect them for mold or signs of rotting. Mold is easy. Rot is more complicated. Rotting tissue will be dark and softer than it should be. 

If you find fungal issues when you inspect, remove all the damaged tubers or portions affected portions. Then, change out the packing material to ensure you don’t leave those microbes in there to affect the rest of your tubers.

Key Takeaways

The most detrimental mistake when storing dahlia tubers is not maintaining the right moisture balance. As long as you keep those bulbs just moist enough to maintain their internal hydration but not enough to encourage fungus, most dahlia varieties should be successful. Remember to keep them cool, keep the air circulating, and keep an eye on them while in storage. 

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