What to Do With Dahlias After They Bloom

Table of Contents

1. Introduction
2. The Art of Deadheading: Keeping the Color Coming
3. Cutting for Bouquets
4. Watching the Weather: The Transition to Autumn
5. How to Lift and Clean Dahlia Tubers
6. Curing and Preparing for Storage
7. Winter Storage: The Goldilocks Method
8. Mid-Winter Checkups
9. Replanting in the Spring
10. Choosing Varieties for Continuous Success
11. Safety and Realistic Expectations
12. Conclusion
13. FAQ

Introduction

There is a unique kind of magic in seeing the first dinnerplate dahlia unfurl its massive, velvety petals in midsummer. These spectacular dahlias are the undisputed champions of the late-season garden, offering a kaleidoscope of colors and shapes that last well into autumn. At Longfield Gardens, we believe that the joy of growing dahlias shouldn't end when the first petals begin to fade. In fact, some of the most rewarding parts of dahlia gardening happen after the peak of the blooming season.

Whether you are a first-time grower or a seasoned gardener with rows of Cafe au Lait blooms, knowing how to manage your plants after they flower is the secret to a long-lasting display. This guide will walk you through the simple steps of deadheading to encourage more blooms, preparing your plants for the winter, and safely storing your tubers for next year. By understanding what to do with dahlias after they bloom, you can ensure your garden stays vibrant all summer and your favorite varieties return even stronger every spring.

The Art of Deadheading: Keeping the Color Coming

The most important thing to do with dahlias immediately after they bloom is a process called deadheading. Deadheading simply means removing flowers that have finished blooming and are starting to fade. This is a simple but powerful task that tells the plant to stop putting its energy into making seeds and instead focus on producing more flower buds.

Dahlias are incredibly generous plants. If you keep them tidy by removing spent blooms, they will often reward you with a continuous supply of flowers from mid-July until the first hard frost. Regular deadheading also keeps the plant looking fresh and prevents pests like slugs or earwigs from hiding in decaying petals.

Identifying the Difference Between a Bud and a Spent Bloom

One of the most common hurdles for new dahlia gardeners is telling the difference between a new flower bud and a spent bloom that has lost its petals. They can look remarkably similar at first glance, but there are two easy ways to tell them apart.

• The Shape: A new flower bud is almost always perfectly round and somewhat flat on top, resembling a small green button. A spent bloom (the part left behind after the petals fall) is usually more conical or pointed. It often looks a bit like a closed-up party cracker.
• The Texture: If you gently squeeze the growth, a new bud will feel firm and solid because it is packed with unexpanded petals. A spent bloom will feel soft or "squishy" to the touch.

Where to Make the Cut

When you find a spent bloom, don't just snip the head off at the very top. To keep your plant looking its best and to encourage strong new stems, trace the flower stem down to where it meets the next set of leaves or a main branch.

Make a clean cut just above that leaf node. This prevents "dead legs"—long, unsightly leafless stems sticking out of your plant. By cutting back to the next set of leaves, you encourage the plant to branch out, resulting in a bushier, more productive dahlia.

Key Takeaway: Deadheading is the best way to extend your dahlia season. Check your plants every few days, remove pointed or squishy spent heads, and always cut back to a leaf node to keep the plant tidy.

Cutting for Bouquets

Another excellent way to manage dahlias after they bloom (or just as they reach their peak) is to cut them for indoor arrangements. Dahlias make some of the best cut flowers in the world because of their sturdy stems and incredible variety.

The rule for dahlias is "the more you cut, the more they bloom." When you harvest flowers for a vase, you are essentially performing a more aggressive form of deadheading. This stimulates the plant to produce even more stems.

For the longest vase life, pick your dahlias in the cool of the morning. Look for flowers that are about three-quarters of the way open. Unlike roses or lilies, dahlias do not open much further once they are cut and placed in water. If you pick a tight bud, it will likely stay a tight bud.

Watching the Weather: The Transition to Autumn

As the days grow shorter and the night air turns crisp, your dahlias will begin to change. While they can handle a light, "vanilla" frost that might nip the very top leaves, a hard frost (where temperatures drop below 32°F for several hours) will signal the end of the growing season.

When a hard frost hits, the foliage of your dahlias will turn black or dark brown almost overnight. While this might look a bit sad, it is actually a vital part of the plant’s life cycle. This process tells the plant to go dormant and begin storing all its energy in the tubers underground.

Why You Should Wait to Dig

It is tempting to grab the shovel as soon as the flowers fade, but patience is a virtue here. We recommend waiting about a week or two after the foliage has turned black before you begin digging up your tubers. During this "waiting period," the tubers undergo a final surge of energy storage and their skins begin to toughen up. This makes them much more resilient during winter storage.

If you live in a very warm climate, check the USDA hardiness zone map because dahlias can often stay in the ground year-round. However, for most of the United States, lifting and storing the tubers is necessary to protect them from freezing.

What to Do Next: Post-Frost Checklist

• Leave the blackened foliage in place for 7–14 days.
• Check your local weather forecast to ensure the ground isn't going to freeze solid.
• Gather your supplies: a garden fork, pruning shears, and labels.
• Label your plants while the stems are still visible so you don't forget which color is which.

How to Lift and Clean Dahlia Tubers

Lifting dahlias is a satisfying autumn chore that ensures you can enjoy your favorite varieties year after year. Think of it as a treasure hunt—that one tuber you planted in the spring has likely multiplied into a large clump of 5 to 10 new tubers.

Step 1: Cutting Back the Stalks

Use a sharp pair of loppers or garden shears to cut the dahlia stalks down to about 4 to 6 inches above the soil line. These short "handles" will make it easier to lift the clump without damaging the individual tubers.

Step 2: Digging With Care

Dahlia tubers grow outward from the center, so you want to avoid stabbing them with your shovel. Use a garden fork if possible, as it is less likely to slice through a tuber than a flat spade. Start digging about 12 inches away from the main stalk, working your way around the plant in a circle. Gently pry upward from several sides to loosen the soil until the clump lifts easily.

Step 3: Removing Soil

Gently shake the clump to remove large chunks of dirt. You can use your hands to brush away excess soil, or a garden hose on a low-pressure setting to wash them clean. It is much easier to see the "eyes" and check for damage when the tubers are clean.

Key Takeaway: Always dig wider than you think you need to. Dahlia tubers are brittle, and a wide circle ensures you don't accidentally chop off the most important parts of the clump.

Curing and Preparing for Storage

Once your tubers are out of the ground and clean, they need to "cure." Curing is simply letting the tubers dry out slightly in a protected area. This helps the skin toughen up and prevents rot during the winter.

Place your tubers in a cool, dry spot away from direct sunlight—a garage or a basement works perfectly. Turn them upside down so that any moisture trapped in the hollow stalks can drain out. Leave them there for 2 to 3 days. They should feel dry to the touch but still remain firm like a fresh potato.

Dividing Your Tubers (Optional)

Many gardeners choose to divide their dahlia clumps in the fall, while others prefer to wait until spring. Dividing simply means cutting the large clump into individual tubers. For a tuber to grow into a new plant next year, it must have three things:

1. The Body: The starchy part that holds the energy.
2. The Neck: The thin part that connects the body to the stalk.
3. The Eye: The small bump on the "crown" (where the neck meets the stalk) from which new growth emerges.

If you are a beginner, we often suggest waiting until spring to divide. By springtime, the "eyes" will begin to swell and turn pink, making them much easier to see.

Winter Storage: The Goldilocks Method

The goal of storing dahlias is to keep them in a "Goldilocks" environment: not too cold (they shouldn't freeze), not too warm (they shouldn't sprout), not too wet (they shouldn't rot), and not too dry (they shouldn't shrivel).

Choosing the Right Storage Medium

To maintain the right moisture balance, you should pack your tubers in a loose material. Some of our favorite options include:

• Vermiculite: Excellent for moisture control and very lightweight.
• Peat Moss: A classic choice that provides good insulation.
• Wood Shavings: Like the kind used for pet bedding; these allow for good airflow.
• Pine Bark: Provides a natural environment for the tubers.

The Storage Container

Place your tubers in a cardboard box, a plastic bin with the lid left slightly ajar, or a breathable bulb crate. Layer the storage medium and the tubers so they aren't touching each other. This prevents one rotten tuber from spoiling the whole batch.

Store the containers in a dark, cool place that stays between 40°F and 50°F. An unheated basement, a root cellar, or a protected crawl space are usually ideal. At our facility in Lakewood, New Jersey, we keep our stock in climate-controlled environments to ensure they stay in prime condition until they are ready to ship to you.

Mid-Winter Checkups

Gardening is a year-round relationship with your plants. We recommend checking on your stored dahlia tubers once a month during the winter. This simple habit can save your entire collection.

• If they look shriveled: They are too dry. Lightly mist the storage medium with water to add a touch of humidity.
• If you see mold or soft spots: They are too wet. Remove any rotting tubers immediately. Increase the airflow by opening the box or moving them to a slightly drier area.
• If they are sprouting: They are too warm. Move them to a cooler spot to keep them dormant until spring.

Replanting in the Spring

When the ground warms up and the danger of frost has passed, it’s time to bring your dahlias back out. You can start them early indoors in pots about 4 to 6 weeks before the last frost, or plant them directly in the garden once the soil temperature reaches about 60°F.

Remember the simple rules for success: choose a spot with at least 6 to 8 hours of full sun and ensure the soil has good drainage—which just means the water doesn't sit in puddles after a rain. With the care you gave them after they bloomed last year, they will be ready to put on an even bigger show this season.

Choosing Varieties for Continuous Success

If you find that you love the process of caring for dahlias, you might want to expand your collection. Choosing a mix of varieties with different bloom times can make the "after-bloom" care even more exciting.

• Border Dahlias: These are shorter and often bloom earlier in the season. They are great for the front of a garden bed.
• Dinnerplate Dahlias: These are the giants of the garden. They take a little longer to start blooming but provide the most spectacular flowers in late summer.
• Cactus dahlias and laciniated dahlias: These have unique, spiky petals that add amazing texture to bouquets.

By mixing these types, you’ll have a staggered blooming schedule, which means you’ll be deadheading and enjoying flowers for a much longer window of time.

Safety and Realistic Expectations

While dahlias are a joy to grow, it is important to remember a few safety and practical notes. First, dahlia tubers can be toxic to cats and dogs if ingested. If you have curious pets, ensure your storage area is secure and out of their reach.

Second, remember that gardening is a partnership with nature. Factors like an unusually wet autumn, an early deep freeze, or very high humidity in your basement can affect how well your tubers survive the winter. Not every tuber will make it every year, and that is perfectly okay. It is part of the learning process. If a favorite variety doesn't return, it simply provides an opportunity to try something new and exciting next season.

Our 100% quality guarantee at Longfield Gardens ensures that any new tubers you order from us will arrive in prime condition and be true to their variety. We want you to feel confident and supported every step of the way, from the first sprout to the final winter storage.

Conclusion

Knowing what to do with dahlias after they bloom is the difference between a one-season wonder and a lifetime of gardening success. By mastering the simple tasks of deadheading during the summer and providing careful storage during the winter, you turn a single tuber into a multi-year investment in beauty. Dahlias are remarkably resilient and eager to please, making them the perfect project for gardeners of all skill levels.

• Deadhead regularly to keep the flowers coming all summer long.
• Wait for the frost to turn foliage black before digging tubers.
• Store in a cool, dry medium like vermiculite or peat moss.
• Check monthly during the winter to ensure your tubers stay firm and healthy.

Growing dahlias is one of the most rewarding experiences a gardener can have. With just a little bit of after-bloom care, you can ensure that your garden remains a spectacular destination for years to come.

The next step is to simply enjoy the process! Keep your shears sharp, your storage boxes ready, and your eyes open for those first beautiful sprouts next spring.

FAQ

How do I tell if my dahlia tuber is still alive in the winter?

A healthy dahlia tuber should feel firm, similar to a fresh potato or a carrot. If you give it a gentle squeeze and it feels solid, it is likely still alive and dormant. If the tuber feels hollow, mushy, or extremely shriveled and dry, it may no longer be viable.

Can I leave my dahlias in the ground if I live in a cold climate?

In areas where the ground freezes (typically USDA zone 7 and colder), dahlia tubers will usually rot or freeze if left in the ground. While a thick layer of mulch can sometimes protect them through a very mild winter, it is much safer to lift and store them indoors to ensure they survive until spring.

Do I need to wash the dirt off the tubers before storing them?

While you don't have to get them perfectly clean, removing the majority of the soil is highly recommended. Soil can hold excess moisture which leads to rot, and it can also hide pests or diseases. A clean tuber is much easier to inspect for "eyes" and overall health during the winter months.

When is the best time to divide my dahlia clumps?

You can divide your dahlias either in the fall right after digging or in the spring before planting. Many gardeners prefer the spring because the "eyes" (the small bumps where growth starts) become much more visible as the tuber wakes up. If you divide in the fall, just be sure each piece has a portion of the crown and an eye attached.