How to Take Cuttings From a Dahlia

Table of Contents

1. Introduction
2. Why Propagate Dahlias From Cuttings?
3. When to Start Your Dahlia Cuttings
4. Gathering Your Supplies
5. Step 1: Waking Up the Tubers
6. Step 2: Taking the Cutting
7. Step 3: Preparing and Sticking the Cuttings
8. Step 4: Providing the Perfect Environment
9. Step 5: Monitoring and Rooting
10. Step 6: Potting Up and Pinching
11. Transitioning to the Garden
12. Realistic Expectations for Success
13. Conclusion
14. FAQ

Introduction

There is a special kind of magic in realizing that a single dahlia tuber can become much more than just one plant. If you have ever fallen in love with a particular flower in your garden, you know the desire to see that color and form repeated in every corner of your yard. Taking cuttings is an enjoyable and rewarding way to multiply your favorite varieties while ensuring they stay true to the parent plant.

At Longfield Gardens, we want to help you grow the most beautiful garden possible. Propagating your own dahlias is a practical skill that allows you to expand your dahlia collection or share starts with friends. This guide will walk you through the entire process, from waking up your tubers in late winter to nurturing young plants that are ready for the spring sun.

Whether you are a beginner or a seasoned gardener, this method is accessible and highly effective. You do not need a professional greenhouse to see great results. With a bit of patience and a few simple supplies, you can significantly increase your flower production for the coming season.

Why Propagate Dahlias From Cuttings?

Many gardeners are familiar with planting dormant dahlia tubers in the spring. This remains the most common way to start these summer favorites. However, taking cuttings offers several unique advantages that make it worth the extra effort in the late winter months.

First, it is an incredible way to increase your stock of a rare or expensive dahlia variety. If you have one highly coveted tuber, taking cuttings can turn that single investment into five, ten, or even more plants in one season. This is much faster than waiting for a tuber to naturally multiply in the ground over several years.

Second, plants grown from cuttings are often exceptionally vigorous. Because they start with fresh, young growth, they tend to establish themselves quickly once planted in the garden. Some growers even find that cutting-raised plants produce more flowers and healthier tubers for the following year.

Finally, taking cuttings is a great insurance policy. If you have a variety that is difficult to store over the winter, starting cuttings early ensures you don't lose that variety if the main tuber fails. It is a productive way to spend the quiet gardening months of February and March while looking forward to the warmth of summer.

When to Start Your Dahlia Cuttings

Timing is the most important factor when you decide to take cuttings. Since dahlias are sensitive to frost, they cannot go into the garden until the soil is warm and all danger of freezing has passed. To have healthy, well-rooted plants ready for transplanting, you should begin the process about 8 to 10 weeks before your local last frost date.

In most parts of the United States, this means starting your tubers indoors sometime in February or March. This window gives the tuber enough time to wake up and produce sprouts. It also allows the cuttings themselves several weeks to develop a strong root system before they move outside.

Because results vary by zone and weather, it is helpful to check your USDA hardiness zone. We time our shipping at Longfield Gardens to ensure your tubers arrive when it is appropriate to start them for your region. If you live in a colder climate, you will simply keep your cuttings indoors under lights a bit longer than someone in a warmer zone.

Key Takeaway: Start your dahlia tubers indoors about two months before your last frost date. This gives you plenty of time to take cuttings and let them root before the garden is ready for planting.

Gathering Your Supplies

You do not need fancy equipment to be successful with dahlia cuttings. Most of these items are likely already in your garden shed or kitchen. Keeping things simple is the best way to ensure you enjoy the process.

• Healthy Dahlia Tubers: Choose tubers that feel firm and plump. Avoid any that feel mushy or completely dried out.
• Shallow Trays or Pots: You will need containers to hold the tubers while they sprout. Seed trays or shallow plastic bins with drainage holes work well.
• Potting Mix: A light, sterile potting soil is ideal. Avoid using heavy garden soil or straight compost, as these can hold too much moisture and lead to rot.
• A Sharp Knife: A clean utility knife or a dedicated garden knife is necessary for making clean cuts.
• Rooting Hormone (Optional): While not strictly required, a rooting powder or gel can help speed up the process.
• Small Pots or Plug Trays: These will hold your individual cuttings while they grow roots.
• Light Source: Because you are starting these in late winter, natural window light is rarely enough. A simple shop light or a dedicated grow light is essential.
• Humidity Dome: This can be a clear plastic lid or even a clear plastic bag placed over your pots to keep the air moist.

Step 1: Waking Up the Tubers

Before you can take a cutting, you need a sprout. This begins by "waking up" your dormant dahlia tubers. Unlike planting them in the garden where they are buried deep, you want these tubers to be easily accessible.

Fill a shallow tray with 2 to 3 inches of moist potting soil. Lay your tubers on top of the soil. You can pack them in fairly closely since they won't be staying here forever. Position them so the "neck" or the "eye" of the tuber is facing upward. This is the spot where the stem will emerge.

Cover the tubers lightly with soil, but leave the very tops or the eyes exposed. This makes it much easier to see the sprouts as they emerge. It also allows you to get your knife right against the tuber when it is time to take the cutting.

Place the tray in a warm spot, ideally around 65°F to 70°F. Keep the soil lightly moist but never soggy. In about two to four weeks, you will see small green "pips" or shoots beginning to grow from the eyes of the tubers.

Step 2: Taking the Cutting

Wait until the new shoots are about 2 to 3 inches tall. They should have at least one or two sets of leaves. This is the ideal size for a cutting; if they get much taller, they can become "leggy" and may not root as easily.

There are two ways to take the cut:

1. The Basal Cutting: This is the most successful method. Use your sharp knife to cut the shoot away from the tuber, taking a tiny sliver of the tuber's skin with it. This woody base contains high concentrations of natural rooting hormones.
2. The Node Cutting: If you don't want to nick the tuber, you can cut the shoot just above the point where it attaches to the tuber. Ensure you leave at least one "node" (the bump where leaves emerge) on the tuber so it can grow more shoots for you later.

Always use a clean, sharp blade. A ragged cut can invite disease or make it harder for the plant to heal. Once you have removed the shoot, the tuber will likely produce even more sprouts from that same spot, allowing you to take several rounds of cuttings over a few weeks.

Step 3: Preparing and Sticking the Cuttings

Once you have your shoot, you need to prepare it for its new life as an independent plant. If the cutting has large leaves, you can carefully trim them in half. This reduces the amount of moisture the plant loses through its leaves while it doesn't have roots to take up water.

Remove any leaves from the bottom inch of the stem. This part will be going into the soil, and you don't want buried foliage to rot. If you are using rooting hormone, dip the bottom of the stem into the powder or gel now.

Prepare your small pots or plug trays with moist, light potting mix. Use a pencil or a small stick to poke a hole in the soil first. This prevents the rooting hormone from being rubbed off when you push the stem in.

Insert the cutting into the hole and gently firm the soil around the base. Make sure the stem is stable and standing upright. Label each pot immediately with the variety name. It is very easy to lose track of which dahlia is which before they bloom!

What to Do Next:

• Trim large leaves to reduce moisture loss.
• Dip the stem in rooting hormone to encourage faster growth.
• Use a pencil to pre-poke holes in the soil.
• Firm the soil gently around the stem for good contact.
• Label your varieties immediately.

Step 4: Providing the Perfect Environment

Your cuttings are now on "life support" until they grow their own roots. Their success depends on three main factors: light, heat, and humidity. Getting these right makes the difference between a wilted stem and a thriving plant.

The 14-Hour Light Rule

Dahlias are very sensitive to the length of the day. In nature, short days tell a dahlia to stop growing leaves and start growing tubers for winter. If your cuttings only get 10 or 12 hours of light, they might try to grow a tiny tuber instead of roots. To keep them in "growth mode," ensure they receive at least 14 to 16 hours of light each day. A simple timer on your grow lights makes this easy to manage.

Managing Temperature

The air around your cuttings should stay between 65°F and 75°F. If the room is too cold, rooting will be very slow. If it is too hot, the cuttings may wilt or rot. Many gardeners find that a seedling heat mat placed under the pots provides the gentle "bottom heat" that encourages roots to grow downward.

High Humidity

Because the cuttings have no roots yet, they must stay hydrated through the air and their stems. Use a humidity dome or a clear plastic bag to trap moisture around the plants. You want the environment to be humid but not dripping wet. If you see heavy condensation, prop the lid open for an hour to let some fresh air circulate. This helps prevent mold and "damping off," a common issue where stems rot at the soil line.

Step 5: Monitoring and Rooting

In about two to three weeks, your cuttings should begin to develop roots. You will know they are successful when you see new green growth appearing at the top of the plant. The leaves will look perkier and more "awake."

Resist the urge to pull on the cuttings to check for roots! This can damage the tiny, fragile root hairs that are just beginning to form. Instead, you can give the stem a very gentle tug after about 14 days. If you feel resistance, it means roots have taken hold in the soil.

If you are using clear plastic cups or orchid pots, you might even be able to see the white roots reaching the edges of the container. Once the roots are well-established, you can gradually remove the humidity dome to let the plants get used to the drier air of your home.

Step 6: Potting Up and Pinching

Once your cuttings have a solid root ball, they are ready to move into a slightly larger container, such as a 4-inch pot. Use a standard high-quality potting mix for this stage. This gives the roots more room to expand and provides the nutrients the plant needs to grow tall and strong.

As the plant reaches about 6 to 8 inches in height, it is time for "pinching." This might feel counterintuitive, but snipping off the very top inch of the main stem encourages the plant to branch out. Instead of one tall, lanky stem, you will get a bushy plant with multiple stems. More stems mean more flowers later in the summer!

Continue to grow your dahlias under lights, keeping the soil moist but not saturated. If the leaves start to look a bit pale, you can use a very diluted, balanced liquid fertilizer once every two weeks.

Transitioning to the Garden

Before your dahlias can go into the ground, they need to be "hardened off." These plants have lived a pampered life indoors, and the transition to wind and direct sun can be a shock.

About a week before you plan to plant, start moving your pots outside to a sheltered, shady spot for an hour or two. Gradually increase their time outside and their exposure to sunlight each day. By the end of the week, they should be ready to stay out overnight.

Plant your dahlias in a sunny spot with well-draining soil. Since these plants already have a head start, you may find they bloom earlier than the tubers you planted directly into the ground. Space them according to the variety's needs—usually about 18 to 24 inches apart for most decorative types.

Key Takeaway: Hardening off is a vital step. Gradually introducing your indoor-grown cuttings to the outdoor elements prevents transplant shock and ensures a successful transition to the garden.

Realistic Expectations for Success

It is helpful to remember that gardening is a living process, and not every cutting will take. Even professional growers rarely get 100% success. If a few of your cuttings wilt or fail to root, do not be discouraged. It is all part of the learning experience.

The health of the original tuber, the temperature of your room, and the consistency of your watering all play a role. If you find that many are rotting, try using a lighter soil mix next time or providing more air circulation. If they are taking too long to root, check that your heat mat is working or that your lights are on for a full 14 hours.

At Longfield Gardens, we believe that the best way to learn is by doing. Every season you take cuttings, you will become more in tune with what your plants need. The joy of seeing a "free" plant that you nurtured from a tiny sprout begin to bloom in July is well worth the effort.

Conclusion

Taking dahlia cuttings is one of the most satisfying ways to spend the early spring. It transforms the way you look at your garden, turning every favorite plant into a potential source for many more. By following these simple steps—starting with healthy tubers, providing the right light and heat, and being patient during the rooting phase—you can fill your yard with stunning blooms.

The process is straightforward:

• Start tubers indoors 8-10 weeks before frost.
• Take 2-3 inch shoots with a sharp knife.
• Keep cuttings under lights for 14+ hours in a humid environment.
• Pinch the tops to encourage bushy growth.
• Harden off carefully before planting outside.

We invite you to try this technique with your favorite varieties this year. It is a wonderful way to grow your garden and your skills at the same time. For more tips on growing beautiful flowers, you can explore our other planning guides and articles.

"There is no greater satisfaction for a gardener than successfully propagating a favorite plant and watching it thrive throughout the summer season."

FAQ

How long does it take for a dahlia cutting to root?

Most dahlia cuttings will develop a functional root system in about two to three weeks. You will know they have rooted when you see new growth at the top of the stem or when the plant feels firm and resistant to a very gentle tug. Consistent warmth and high humidity are the keys to speeding up this timeframe.

Do I need a greenhouse to take dahlia cuttings?

No, you do not need a greenhouse to be successful. Many gardeners take cuttings on a simple shelf in a basement, spare room, or garage. As long as you can provide a consistent temperature of around 70°F and a strong light source for 14 to 16 hours a day, your cuttings will do very well indoors.

Can I take cuttings from a dahlia plant growing in the garden?

While it is possible to take cuttings in the summer, it is much more difficult. Summer cuttings are often "hollow" in the center, which makes them prone to rotting before they can root. The best, most successful cuttings are the solid "basal" shoots that emerge directly from the tuber in the spring.

Will a plant from a cutting produce a tuber for next year?

Yes, a dahlia grown from a cutting will produce a brand-new tuber by the end of the growing season. In many cases, these tubers are clean, healthy, and very easy to store. You can then dig up, store, and even divide these new tubers just like you would with any other dahlia plant.