Introduction
Growing dahlias is one of the most rewarding experiences a gardener can have, especially when those first dinnerplate-sized blooms begin to open in midsummer. There is a special kind of magic in watching a small tuber transform into a towering plant filled with intricate, colorful flowers. While most gardeners start with tubers, learning how to grow dahlias from cuttings is a simple and enjoyable way to expand your collection.
At Longfield Gardens, we enjoy helping gardeners discover how easy it is to multiply their favorite varieties. Taking cuttings allows you to create exact clones of your best plants, ensuring you have plenty of flowers for your garden and for cutting jars. This technique is perfect for anyone who wants more plants without needing more storage space for over-wintered tubers.
This guide will walk you through the entire process, from waking up your tubers in late winter to planting your rooted cuttings in the garden. You will learn the best environment for root development and how to care for these young plants as they grow. By following these steps, you can confidently turn one dahlia plant into many.
Why Grow Dahlias from Cuttings?
Taking cuttings is a standard practice for many professional growers, but it is just as accessible for home gardeners. The primary benefit is the ability to multiply your stock quickly. If you have a specific variety you love, such as a soft peach "Cafe au Lait" or a vibrant "Labyrinth," taking cuttings allows you to turn one tuber into five or ten plants in a single season.
Cuttings also tend to grow very vigorously. Because they start with a developed root system and no old tuber material to potentially carry rot, these plants often establish themselves quickly in the garden. Many gardeners find that plants grown from cuttings actually bloom earlier than those grown from tubers because they have a "head start" in a controlled, warm environment.
Furthermore, cuttings are an excellent way to save a variety if the parent tuber is small or shows signs of shriveling. By "waking up" the tuber early and taking cuttings, you ensure the genetics of that plant live on in healthy, new offspring. It is a productive, low-cost way to fill your landscape with color.
Supplies You Will Need
Before you begin, gather your materials so the process goes smoothly. You do not need expensive equipment, but having the right tools on hand makes the work easier and more successful.
- Dahlia Tubers: Choose healthy, firm tubers with visible "eyes" or those that are already starting to sprout.
- Growing Medium: A sterile, soil-less mix is best. You can use a seed-starting mix or a blend of peat moss and perlite. The goal is a medium that holds moisture but allows for excellent drainage.
- Containers: Use shallow trays or crates to "wake up" the tubers, and small 2-inch to 3-inch pots or cell trays for the cuttings themselves.
- A Sharp Knife: A dedicated garden knife, a scalpel, or even a clean utility knife works well. It must be very sharp to make clean cuts without crushing the delicate plant tissue.
- Rooting Hormone (Optional): While not strictly necessary, a dipping powder or gel can help speed up the rooting process.
- Light Source: Dahlias are sensitive to light duration. A shop light or a dedicated grow light is essential for indoor starting.
- Humidity Dome: A clear plastic cover helps keep the air around the cuttings moist while they develop roots.
Key Takeaway: Using sterile tools and a clean growing medium is the simplest way to prevent common issues like damping off. Start with clean equipment to give your cuttings the best environment possible.
Step 1: Waking Up the Tubers
To take cuttings, you must first encourage your tubers to produce shoots. This process usually begins in late winter or early spring, about 8 to 10 weeks before your last expected frost date.
Place your tubers in a shallow tray filled with damp potting soil or peat moss. You do not need to bury them deeply; leaving the "neck" and the "crown" (where the eyes are located) slightly exposed makes it easier to see and harvest the shoots later. Place the tray in a warm spot, ideally between 65°F and 70°F.
Light is not necessary for the tubers to sprout, but once the first green "pips" appear, move the tray under grow lights. Keep the soil lightly moist but never soggy. In a few weeks, the eyes will grow into sturdy green shoots. When these shoots reach about 3 to 4 inches in height and have at least two sets of leaves, they are ready to be harvested as cuttings.
Step 2: Taking the Cutting
There are two main ways to take a dahlia cutting: the basal cut and the node cut. The basal cut is often preferred because it includes a tiny piece of the tuber itself, which contains a high concentration of natural growth hormones.
The Basal Cut
To take a basal cutting, use your sharp knife to slice the shoot away from the tuber, taking a very thin sliver of the tuber tissue with it. Be careful not to gouge the tuber deeply, as you want it to continue producing more shoots. This small piece of "woody" material at the base of the shoot is where roots will often form most rapidly.
The Node Cut
If the shoot is growing further up a stem or if you want to leave the base of the shoot so it can branch and produce more cuttings, you can take a node cut. Simply cut the shoot just below a leaf node (the bump on the stem where leaves emerge). Roots will grow from this node once it is tucked into the soil.
Regardless of the method, ensure your knife is sterilized between different varieties. A quick dip in a mild bleach solution or rubbing alcohol prevents the spread of any potential pathogens from one plant to another.
Step 3: Preparing and Potting the Cuttings
Once you have removed a shoot, it needs a little preparation before it goes into its rooting container. If the shoot has large leaves, you may want to trim them in half with your scissors. This reduces the surface area, which helps the cutting retain moisture while it has no roots to draw up water.
Remove the lowest set of leaves near the base of the cut. This creates a clean "stem" that can be inserted into the soil. If you are using rooting hormone, dip the bottom half-inch of the stem into the powder or gel.
Make a small hole in your damp potting mix using a pencil or a small stick. Insert the cutting so the bare node or the basal sliver is about an inch deep. Gently firm the soil around the stem to ensure there are no air pockets. Good contact between the soil and the stem is essential for root development.
What to do next:
- Label your pots immediately so you don't lose track of the variety.
- Group your pots together to make maintaining humidity easier.
- Check the soil moisture; it should feel like a wrung-out sponge.
Step 4: Creating the Right Environment
The first two weeks are the most critical for a new cutting. Since it has no roots, it relies entirely on the moisture in the air and the dampness of the soil to stay hydrated.
Humidity and Temperature
Place your pots under a clear humidity dome or inside a clear plastic bag held up by stakes. This creates a mini-greenhouse effect. Keep the temperature consistent, between 65°F and 75°F. If your workspace is chilly, a waterproof seedling heat mat can provide the gentle bottom heat that encourages roots to grow faster.
The 14-Hour Light Rule
One of the most important factors in growing dahlias from cuttings is the length of the "day." Dahlias are photoperiodic, meaning they react to the number of hours of light they receive. If the days are too short (less than 12 hours), the plant may try to form a tiny tuber instead of growing roots and leaves.
To keep the plant in "growth mode," ensure your cuttings receive at least 14 to 16 hours of light per day. A simple timer on your grow lights makes this easy to manage. The light doesn't need to be intensely bright, but it must be consistent.
Step 5: Caring for Rooting Cuttings
After about 10 to 14 days, your cuttings should begin to form roots. You will know they are successful when you see new, bright green growth at the top of the shoot. Another way to check is to give the cutting a very gentle tug; if you feel resistance, roots have begun to anchor the plant into the soil.
Once roots are established, you can gradually remove the humidity dome. Start by propping it open for a few hours a day, eventually removing it entirely over the course of a week. This "hardens" the plant to the lower humidity of your home or greenhouse.
Watering at this stage should be careful. You want the soil to stay moist, but as the roots grow, they need oxygen as much as they need water. Allow the top half-inch of the soil to dry out slightly before watering again. If the leaves look dark green and the plant is standing tall, your watering routine is likely correct.
Step 6: Potting Up and Feeding
As the roots begin to fill the small starter pots, it is time to move the dahlias into a slightly larger container, such as a 4-inch or 5-inch pot. This gives the roots more room to expand and provides more nutrients for the growing plant.
Use a high-quality potting soil for this transition. Because dahlia cuttings grow quickly, they can be "heavy feeders." Once the plant is established in its new pot, you can begin using a balanced, water-soluble fertilizer at half-strength every two weeks. This supports the development of strong stems and lush foliage.
At our trial garden at Longfield Gardens, we have found that cuttings often produce a very dense root ball quite quickly. Moving them to a larger pot before they become root-bound ensures they don't experience a growth check. A healthy, growing plant is much more resilient when it finally moves outdoors.
Step 7: Transitioning to the Garden
Before your cuttings can live outside, they must be "hardened off." This is the process of gradually acclimating them to outdoor temperatures, wind, and direct sunlight. Sunlight through a window or under a grow light is much less intense than direct summer sun, and young leaves can scorch if moved too quickly.
Start by placing your pots in a shaded, protected spot outdoors for an hour or two on a calm day. Gradually increase the time they spend outside and the amount of sunlight they receive over 7 to 10 days. If a late spring frost is predicted, bring them back inside for the night.
Once the danger of frost has passed and the soil has warmed to about 60°F, you can plant your dahlias in the garden. Space them just as you would plants grown from tubers, usually about 18 to 24 inches apart depending on the variety.
Key Takeaway: Patience during the hardening-off phase is the secret to a seamless transition. Taking a week to ease your plants into the outdoor world prevents transplant shock and keeps them growing strong.
Planting Tips for Cuttings
When you plant your rooted cuttings, you can actually set them slightly deeper in the ground than they were in their pots. If you remove the lowest set of leaves and bury that node under the soil, the plant will often develop extra roots and eventually form more tubers from that point.
Because cuttings do not have the energy reserves of a large tuber, they need consistent moisture during their first few weeks in the ground. Mulching around the base of the plant can help retain soil moisture and keep the roots cool. If the weather is particularly hot and dry right after planting, provide a bit of temporary shade during the afternoon until the roots find their way deep into the garden soil.
Support is also important. Even though cuttings start small, they will eventually grow into full-sized plants. It is much easier to place a stake or a tomato cage at the time of planting than it is to try to support a heavy, blooming plant later in the season.
What to Expect from Cutting-Grown Dahlias
A common question is whether a cutting will produce tubers for the following year. The answer is a resounding yes! By the end of the first growing season, a plant grown from a cutting will have developed a cluster of tubers at its base. These can be dug up and stored over the winter just like any other dahlia tubers.
In many cases, the blooms on cutting-grown plants are indistinguishable from those grown from tubers. In fact, some varieties that are slow to "wake up" from a tuber may actually bloom earlier when started as a cutting because the plant was already several inches tall when it went into the ground.
You may also notice that cutting-grown plants are very bushy. Since they start from a single stem that often branches early, they can create a very full, lush look in the border. Watching these small starts grow into flowering giants is one of the most satisfying parts of the gardening year.
FAQ
How long does it take for a dahlia cutting to root?
Most dahlia cuttings will develop a functional root system within 10 to 21 days. The exact timing depends on the temperature, the health of the shoot, and whether you use a rooting hormone. You will know they have rooted when you see new leaf growth and feel resistance when you gently tug on the stem.
Can I take cuttings from a dahlia plant in the garden?
Yes, you can take cuttings from a growing plant in midsummer, though they may not have enough time to form large tubers before frost. These are often called "green cuttings." The process is the same: cut below a node, remove lower leaves, and keep the cutting in a humid, bright environment until roots form.
Do I need a greenhouse to grow dahlias from cuttings?
No greenhouse is necessary. Many successful gardeners grow their cuttings on a simple shelf with a shop light and a plastic cover. As long as you can maintain a warm temperature and provide 14 hours of light, your cuttings will thrive indoors until it is time to move them outside.
Why are my cuttings wilting even though the soil is wet?
Wilting in wet soil is usually a sign that the humidity is too low or the roots are struggling with "damping off" due to a lack of oxygen. Ensure you are using a humidity dome to keep the air moist, and make sure your potting mix is light and well-draining so the roots can breathe.
Conclusion
Growing dahlias from cuttings is an accessible and rewarding way to fill your garden with color and beauty. It transforms the way you think about your plants, allowing you to see one tuber as the starting point for a whole landscape of blooms. By focusing on simple basics—clean cuts, consistent humidity, and the right amount of light—you can successfully multiply your favorite varieties and share them with friends and neighbors.
- Start with healthy, sprouted tubers in late winter.
- Provide 14–16 hours of light to ensure the plants stay in growth mode.
- Maintain high humidity until the roots are well-established.
- Hardening off is the most important step for a successful move to the garden.
Gardening is a journey of discovery, and propagation is one of its most exciting chapters. We invite you to try this method with your favorite varieties this season. If you ever have questions about your plants or need advice on choosing the best varieties for your climate, reach out to us at Longfield Gardens.
Taking dahlia cuttings is a simple skill that pays off in abundance. With a little patience and the right environment, you can turn a single favorite plant into a spectacular summer display.
