How to Overwinter Dahlia Tubers (So They Come Back Next Year)

Learn how to overwinter dahlia tubers in cold climates. My step-by-step method shows how to lift, cure, store, and replant them for blooms next year.

After gardening for nearly 30 years here in my Zone 6b New Jersey garden, and growing dahlias for the last eight, I’ve learned one important truth: once our autumn temperatures start to drop, dahlias and other tender bulbs simply won’t survive the winter outdoors. They thrive beautifully all summer, but once frost arrives, the tubers will rot if they’re left in the ground.

That’s why overwintering is essential in cold climates like mine. And while lifting and storing tubers may seem like extra work, it’s absolutely worth the effort. You’ll save money, preserve your favorite varieties, and keep those special dahlias you’ve fallen in love with from season to season.

If you’re new to growing dahlias, make sure to visit my Complete Dahlia Growing Guide and How to Plant Dahlia Tubers so you’re familiar with their full life cycle. But if you’re ready to learn exactly how I lift, clean, cure, and store my tubers all winter long here in Zone 6b, this guide will walk you through every step.

Let’s dig in (literally!) and save those dahlias for another beautiful season of blooms.

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Understanding Tender Bulbs & Why Overwintering Matters

Tender bulbs, tubers, and corms (like dahlias, gladiolus, caladiums, and cannas) are beloved for their bold summer color. But unlike true hardy bulbs, they cannot survive freezing temperatures. Here in my Zone 6b New Jersey garden, winter soil temps drop far too low for dahlias to remain in the ground, which means they’ll rot if left outside.

For gardeners in cold climates, overwintering isn’t just a “nice to do.”
It’s the only way to carry your favorite dahlias into the next growing season, preserve varieties you love, and avoid repurchasing expensive tubers every spring. Cause let’s be honest here…those tubers are expensive!

And trust me, once you get the hang of it, overwintering becomes a natural part of your yearly routine.

Why Overwinter & Store Your Dahlia Tubers?

Dahlia tubers aren’t cheap, especially if you love the unique or specialty varieties (guilty!). Overwintering allows you to:

• Protect your investment rather than buying new tubers each year
• Save your favorite varieties that perform beautifully in your garden
• Multiply your collection — healthy tubers divide over time
• Grow rare or hard-to-find dahlias without breaking the bank
• Start the next season strong with mature, proven plants

If you’re a cut-flower gardener, overwintering is an absolute game-changer because it ensures earlier and more abundant blooms the following year.

The Dahlia Dilemma: Do You Have to Overwinter?

A common question I hear is: “Do dahlias come back every year?” The answer depends entirely on your growing zone.

• Zones 7–10:
  You may be able to leave dahlias in the ground with a very thick winter mulch. Some years they make it… some years they don’t.
• Zones 6 and colder (like my 6b garden):
  Dahlias must be lifted and stored indoors if you want them to survive. We simply freeze too hard for tubers to overwinter in the soil.

I’ve been storing dahlias for years now, and while it’s a bit of work, it’s always worth it. Mature dahlia clumps often return bigger and better — and they multiply, so you may even gain more plants than you started with.

And yes, the same rule applies to dahlias grown in containers in cold climates. Pots offer no insulation, so tubers must be removed and stored, or treated as annuals. (For more information about growing dahlias in pots, please visit How to Grow Dahlias in Pots

Lifting & Storing Dahlia Tubers

Alright, let’s get down to business. Here in New Jersey, we need to dig up our precious dahlia tubers before the ground freezes.

Supplies Needed

While digging up dahlia tubers is fairly simple, there are a few things you need to store them. The tubers are a bit finicky when overwintering, so they must be treated with extra care if you want them to survive the winter.

Here’s what you need.

• Garden Spray Nozzle
• Garden Fork
• Pruners or Loppers
• Plant tags
• Crates, cardboard boxes and/or brown paper bags
• Sphagnum Peat
• Garden Hose

Before the First Frost

Label your plants: This is crucial if you have multiple varieties, especially dahlias. Trust me, you don’t want to be playing guessing games in the spring. I have dug up many tubers and not recalled which variety they are so label them well before the first frost

After the First Frost: Lifting and Storing Dahlia Tubers

Cut back the foliage

Leave about 4-6 inches of stem so you have something to grab onto when you’re digging.

Carefully dig up the bulbs/tubers

Use a garden fork to loosen the soil and gently lift the bulbs or, in the case of dahlias, the dahlia tubers out. Be careful not to damage them!

Hose off the excess soil

Give those bulbs/tubers a good rinse to remove any dirt or debris.

Inspect for damage

Discard any bulbs/tubers that are shriveled, soft, or diseased.

Dry them out

Let the bulbs/tubers dry in a frost-free location for a few days. Don’t stack them too high, or they might bruise each other.

Trim and clean

Once they’re dry, remove any remaining soil and cut the stems back to about an inch. Make sure the inside of the stem is dry too.

Packing & Storing Dahlia Tubers and Other Tender Bulbs

1. Label everything: Seriously, don’t skip this step! You’ll thank yourself later.
2. Pack them up: Place similar bulbs/tubers together in cardboard boxes or paper bags. Use packing material like sphagnum peat to cushion them and prevent damage.
3. Find a cool, dry spot to store dahlia tubers and other bulbs: Ideally, you want a temperature between 45-55 degrees F. A basement or unheated garage works well.

Winter Check-Ups: How to Keep Tubers Healthy Until Spring

One thing I’ve learned after overwintering dahlias for several years is that the job isn’t done once the tubers go into storage. Conditions shift throughout winter, and a quick monthly check can make the difference between thriving tubers and a bin of mush.

Here’s what I do:

• Inspect tubers monthly for any signs of rot, mold, or excessive shriveling.
• If they look dry or wrinkled, lightly mist the packing material with water—just enough to add humidity without making anything damp.
• If you spot rot, remove the affected area with clean pruners and discard any tubers too far gone. This prevents the issue from spreading.
• Maintain consistent temperatures (ideally 40–50°F). Overly warm spaces cause sprouting; overly cold spots risk damage.

These simple winter check-ins have saved many of my tubers over the years, especially rare varieties I don’t want to lose.

Springtime! Replanting Your Overwintered Dahlias

Once your last frost date has passed, it’s finally time to wake those dahlias up and get them growing again. Here in my Zone 6b garden, that’s usually late April into early May, but always double-check your own frost date before planting.

If you want blooms a little earlier, you can pre-sprout your dahlias indoors in late February or early March. I only recommend this if you have the space and discipline to monitor moisture levels closely—tubers rot easily when started too early.

For a full walkthrough on timing, planting depth, soil prep, and troubleshooting, read my complete tutorial: How to Plant Dahlia Tubers Like a Pro

And if you’re growing dahlias specifically for cut flowers, you may also find my pillar post helpful: How to Care for Dahlia Flowers

My First Dahlia Overwintering Adventure

I’ll never forget the first time I overwintered dahlias. As someone gardening in Zone 6b, I knew I had to lift the tubers if I wanted them to survive—but I was honestly intimidated. Dahlias have a reputation for being a little fussy, and I wasn’t sure I’d get it right.

To my surprise, most of my tubers made it through that first winter beautifully. A few didn’t survive (which is completely normal), but the ones that did rewarded me with even bigger, healthier plants the following summer. That experience gave me the confidence to keep refining my process—and each year since, my success rate has improved.

If you’re nervous about trying this for the first time, please know: you don’t have to get it perfect to succeed. Even with a few mistakes, overwintering can be incredibly rewarding.

Mistakes I’ve Made (and How You Can Avoid Them)

Mistake 1: Storing Tubers When They Were Still Too Wet

During my first few years overwintering dahlias, I didn’t let the tubers cure long enough before storing them. When tubers go into storage damp, they are far more likely to develop mold or rot.

How to Avoid It:
Allow tubers to cure for 1–3 days in a cool, shaded spot until the skin feels leathery, not moist.

Mistake 2: Forgetting to Check Them During Winter

There was one year when I didn’t check my tubers for more than two months, and I lost several that could have been saved.

How to Avoid It:
Check stored tubers every 3–4 weeks for shriveling, mold, or rot.

Mistake 3: Storing Tubers Somewhere Too Warm

Tubers stored in warm conditions will begin sprouting prematurely. I learned this the hard way by keeping mine too close to the furnace one winter.

How to Avoid It:
Store tubers in a consistently cool area between 40–50°F.

Mistake 4: Not Labeling Tubers

Every tuber looks the same in February. Trust me—once you mix them up, it’s impossible to know which variety is which.

How to Avoid It:
Label each clump immediately when you lift it from the garden.

Mistake 5: Leaving Too Much Soil on the Tubers

Leaving clumps overly muddy increases the chances of rot in storage.

How to Avoid It:
Gently remove most of the soil before curing, but don’t wash them completely.

Troubleshooting Common Dahlia Overwintering Problems

Problem: Tubers Are Shriveling or Drying Out

Shriveled tubers are dehydrated.

What to Do:
Lightly mist the packing medium, add slightly damp peat moss or vermiculite, and check the tubers more frequently. Slight shriveling is normal; severe shriveling may not be reversible.

Problem: Tubers Are Getting Moldy or Soft

This usually indicates too much moisture or poor ventilation.

What to Do:
Remove affected areas with clean pruners, refresh the packing material, improve airflow, and move the tubers to a cooler, drier location. Fully mushy tubers should be discarded.

Problem: Tubers Are Sprouting Early

Early sprouting occurs when storage temperatures are too warm.

What to Do:
Move them to a cooler space, ideally 40–50°F. You can trim back sprouts to about an inch without harming the tuber.

Problem: Tubers Have No Visible Eyes

Sometimes eyes simply aren’t visible yet.

What to Do:
Move them to a slightly warmer spot (around 55–60°F) for a week to encourage eyes to form. Older tubers that never develop eyes are unlikely to grow and should be discarded.

Problem: Tubers Rot After Replanting in Spring

Rotting after planting typically happens when the soil is too cold or too wet.

What to Do:
Wait until soil temperature reaches at least 60°F, plant in well-draining soil, and avoid watering until new growth appears.

Final Thoughts About Overwintering Dahlias

After several years of overwintering dahlias here in my Zone 6b garden, I’ve learned that storing tubers doesn’t have to be all-or-nothing. Some seasons, I save every single variety because I want to expand my collection or protect harder-to-find favorites. Other years—especially when fall is busy—I only overwinter the dahlias that are truly special to me and simply buy new tubers in spring. There is no “right” way to do this. It really depends on your time, energy, and gardening goals.

The beauty of overwintering is that it gives you options. Saving tubers absolutely helps reduce costs, and it’s incredibly rewarding to see your dahlias come back stronger each year. But it’s also perfectly fine to treat dahlias like annuals when life calls for a simpler gardening season. What matters most is growing the varieties you love and creating a garden that brings you joy.

If you’re growing dahlias as part of a larger cut flower garden, you may also find my Cut Flower Gardening for Beginners guide helpful as it walks you through choosing varieties, planning your space, and harvesting blooms for arrangements. And if you need a refresher on the full dahlia life cycle, my Dahlia Growing Guide and Planting Dahlia Tubers post will walk you through the next steps.

If your plants have a lot of foliage but not producing buds or flowers yet, see my guide on why dahlias may not be blooming for simple fixes you can try.

No matter which route you choose, saving tubers or starting fresh, dahlias will always reward you with unforgettable color, texture, and beauty in the summer garden. If you have questions or want to share your own overwintering successes (or failures!), I’d love to hear about them in the comments.

For more information about lifting dahlia tubers for winter, read this article from Washington State University.

Thanks for stopping by the blog today!

Enjoy your day! xoxo