Table of Contents
- Introduction
- Why Summer is a Great Time for Cuttings
- Understanding the Two Types of Dahlia Cuttings
- When Exactly Should You Take Summer Cuttings?
- Step-by-Step: How to Take Summer Dahlia Cuttings
- The Secret to Success: Creating the Perfect Rooting Environment
- How Long Does Rooting Take?
- Transitioning Your Cuttings to the Garden
- Challenges of Late Summer Cuttings
- Maximizing Your Flower Harvest
- Soil and Fertilizer Needs for New Cuttings
- A Note on Variety Success
- Conclusion
- FAQ
Introduction
There is nothing quite like the sight of a dahlia garden in full swing. When those first dinnerplate-sized blooms begin to open in mid-summer, it is natural to want even more of them to fill every corner of your yard. The good news is that you do not have to wait until next spring to expand your collection. While many gardeners think propagation is strictly a springtime activity, summer offers a wonderful window to grow your garden for free.
At Longfield Gardens, we believe that every gardener should feel empowered to experiment with their plants, and reliable favorites like Cornel are a great place to start. Dahlias are remarkably resilient and vigorous growers, especially once the soil has warmed up and the days are long. Taking cuttings in the summer is one of the easiest ways to turn a single healthy plant into a dozen beautiful clones. Whether you want to fill a new garden bed or share your favorite varieties with neighbors, the process is straightforward and incredibly rewarding.
This guide will walk you through the simple steps of identifying the best shoots, rooting them successfully, and ensuring they grow into strong plants before the season ends. We will cover the specific needs of summer cuttings and how to manage the transition from a small snip to a flowering beauty. By the end of this article, you will see that summer propagation is a practical skill that any home gardener can master.
Propagating dahlias from cuttings during the summer months is an effective and enjoyable way to multiply your favorite varieties while maintaining a healthy, bushy garden.
Why Summer is a Great Time for Cuttings
Most gardening books suggest taking dahlia cuttings in early spring when the tubers are first waking up. While that is a great time to start, summer offers several unique advantages. By June or July, your dahlia plants are in their peak growth phase. They are full of energy, pumping nutrients through their stems, and ready to produce new cells at a rapid pace.
One of the best reasons to take cuttings now is the "pinching" process. Many experienced dahlia growers pinch off the top few inches of their plants when they reach about 12 to 18 inches tall. This encourages the plant to grow bushier and produce more flower stems. Instead of throwing those pinched tops on the compost pile, you can turn them into brand-new plants.
Summer cuttings also provide a safety net. If you have a particularly rare or favorite variety, having a few "backup" plants growing in pots can be a lifesaver if the mother plant is damaged by a storm or a pest. Since the weather is already warm, you do not need to worry about heating mats or complicated indoor setups. With just a little shade and some water, nature does most of the hard work for you.
Key Takeaway: Summer cuttings allow you to recycle the growth you would normally prune away, giving you "free" plants that are genetically identical to your favorite dahlias.
Understanding the Two Types of Dahlia Cuttings
Before you grab your garden snips, it helps to understand the two main ways to take a dahlia cutting. While the end goal is the same—a rooted plant—the method changes depending on where you take the cutting from.
Basal Cuttings
Basal cuttings are taken from the very base of the plant, right where the stem meets the tuber. These are typically the strongest cuttings because they often include a tiny piece of the "crown" or tuber tissue. This tissue is packed with growth hormones that tell the plant to start making roots immediately. In summer, you can still find these shoots emerging from the base of established plants. You may need to gently brush away a little bit of soil to see where the stem attaches to the tuber.
Stem Cuttings
Stem cuttings (also called terminal cuttings) are taken from the mid or top sections of a growing plant. When you pinch the top of a dahlia to make it branch out, you are taking a stem cutting. These do not have the advantage of tuber tissue, but they are still very easy to root because the plant is in an active state of "softwood" growth. Softwood refers to the fresh, green, flexible growth of the current season. This tissue is much more likely to root than the older, hollow, woody stems found at the bottom of the plant later in the year.
When Exactly Should You Take Summer Cuttings?
Timing is everything when it comes to summer propagation. For the best results, aim for the window between early June and late July. During this time, the days are at their longest, which provides the light energy necessary for the cutting to establish a root system.
If you take cuttings too late in the year—such as late August or September—the plant will still grow and might even produce a flower. However, it may not have enough time to develop a "storage tuber" before the first frost. Dahlias need several months of growth to store the energy required to survive winter dormancy. Cuttings taken in early summer have a much higher chance of forming a viable tuber that you can dig up and save for next year.
Step-by-Step: How to Take Summer Dahlia Cuttings
Taking a cutting is a simple process, but doing it with care ensures a much higher success rate. Follow these steps to get your new plants started on the right foot.
1. Gather Your Tools
You do not need a laboratory to propagate dahlias, but clean tools are essential. You will need:
- A very sharp, clean knife or a pair of micro-tip garden snips.
- Small pots (3 to 4 inches wide) with plenty of drainage holes.
- A high-quality, professional-grade potting mix or a "soilless" medium like perlite or vermiculite.
- Optional: Rooting hormone (powder or gel) to speed up the process.
2. Select the Right Shoot
Look for a healthy, vigorous stem that is about 3 to 5 inches long. It should have at least two or three sets of leaves. Avoid stems that already have a large flower bud at the tip, as the plant will try to put its energy into blooming rather than growing roots. If the only available shoots have buds, simply pinch the bud off before you proceed.
3. Make the Cut
If you are taking a basal cutting, cut as close to the tuber as possible, ideally taking a sliver of the tuber with it. If you are taking a stem cutting, make your cut just below a "node." A node is the bump on the stem where the leaves emerge. This area is a powerhouse of growth cells, and roots are most likely to sprout from this specific spot.
4. Prepare the Cutting
Once you have your stem, remove the bottom set of leaves. This leaves you with a bare section of stem at the bottom and a few leaves at the top. If the remaining leaves are very large (common in dinnerplate varieties), you can trim them in half with your scissors. This might look strange, but it reduces the amount of moisture the cutting loses through its leaves while it has no roots to drink with.
5. Planting and Rooting
Dip the bottom node of the cutting into water, then into your rooting hormone if you are using it. Use a pencil or a "dibber" to make a hole in your potting mix, then gently insert the cutting. Firm the soil around the stem so it stands upright.
What to Do Next:
- Label your pots immediately so you don't forget which variety is which.
- Water the potting mix thoroughly until water runs out the bottom.
- Place the pots in a bright spot but away from direct, scorching sunlight.
- Mist the leaves daily to keep the humidity high around the cutting.
The Secret to Success: Creating the Perfect Rooting Environment
Once the cutting is in the pot, your job is to keep it comfortable while it performs the "magic" of growing roots. Because the cutting has no root system yet, it cannot replace the water it loses to the air. This is why humidity is your best friend.
Managing Humidity
A simple way to keep humidity high is to create a "mini-greenhouse." You can place a clear plastic bag over the pot or use a plastic humidity dome. Just make sure the plastic does not touch the leaves, as this can lead to rot. If you see too much condensation (big droplets of water) building up, open the bag for an hour to let some fresh air in.
Getting the Light Right
While mature dahlias love 6 to 8 hours of direct sun, a fresh cutting will wilt and die in those conditions. Place your cuttings in a spot that receives "bright, indirect light." A porch, the shadow of a larger plant, or a spot near a north-facing window is ideal. You want enough light to signal the plant to grow, but not enough heat to cook it.
Temperature and Airflow
Dahlias root best when the air temperature is between 65°F and 75°F. If your summer is particularly hot, keep the cuttings in a cooler, shaded area. Good airflow is also important to prevent mold or "damping off," which is a common issue where the stem rots at the soil line. If the soil feels soggy, stop watering for a day and move the pot to a spot with better air circulation.
How Long Does Rooting Take?
Patience is a virtue in the garden, but fortunately, dahlias are relatively fast. You can expect to see the first signs of success in about 2 to 4 weeks.
How do you know if it is working? Resist the urge to pull on the cutting to check for roots! This can snap the tiny, fragile new root hairs. Instead, look for new growth at the very top of the stem. If the cutting starts producing tiny new green leaves, it is a sure sign that roots have formed underneath and are now supporting the plant.
Another trick is to use clear plastic cups (with holes poked in the bottom) instead of traditional pots. This allows you to see the white roots as they reach the edges of the container without disturbing the plant.
Transitioning Your Cuttings to the Garden
Once your cutting has a robust root system—usually about 4 to 6 weeks after you started—it is time to move it to its permanent home. However, you cannot move it directly from its protected, humid spot into the full summer sun without a transition period. This process is called hardening off.
The Hardening Off Process
- Days 1-2: Move the pot to a spot outside that is fully shaded and protected from the wind for a few hours.
- Days 3-4: Give the plant an hour or two of morning sun, then move it back to the shade.
- Days 5-7: Gradually increase the amount of sunlight and time spent outdoors.
- Day 8: If the plant looks strong and is not wilting, it is ready to be planted in the ground.
When you plant your rooted cutting, treat it like any other dahlia. Choose a spot with well-draining soil and plenty of sun.
Challenges of Late Summer Cuttings
As we mentioned earlier, the main challenge with summer cuttings is the "race against the clock." In many parts of the US, the first frost arrives in October or November. This gives a July cutting about three to four months to grow.
While the plant may produce a few beautiful flowers in September, its primary job is to grow a tuber underground. If you find that your summer cuttings are still very small when the first frost hits, do not worry. You can often dig up the small "clump" and store it just like a regular tuber. Some gardeners even prefer to bring these small potted dahlias indoors and keep them on a sunny windowsill over the winter to get a massive head start the following spring.
We work with growers to ensure our plants have the best genetics for vigor, but environmental factors like your local frost date will always play a role in how a summer cutting performs. If you live in a warm climate, the USDA Hardiness Zone Map will help you compare your region with colder northern zones.
Maximizing Your Flower Harvest
One of the most exciting parts of taking summer cuttings is the "bonus" flowers you receive. A cutting taken in June can often reach 2 or 3 feet in height by late September. Because cuttings are essentially clones of a mature plant, they often skip the "awkward teenage phase" and get right to the business of blooming.
If you are growing dahlias for cut flowers, having these extra plants is a game-changer. It allows you to be more aggressive with your harvesting on the main plants while the cuttings provide a second wave of blooms. Varieties like Café au Lait or Cornel are famous for their productivity, and having three or four extra plants of these varieties can mean the difference between one bouquet a week and five.
Soil and Fertilizer Needs for New Cuttings
When your cutting is first rooting, it does not need fertilizer. In fact, heavy fertilizers can burn the tender new roots. The cutting is currently living off the energy stored in its own stem and leaves.
Once the plant is moved into the garden and shows active growth, you can begin a light feeding schedule. A balanced, water-soluble fertilizer or a specialized bloom booster can help the plant catch up to its older siblings. Just remember our rule for watering: deep and consistent is better than frequent and shallow. This encourages the roots to grow deep into the soil, making the plant more drought-tolerant during the heat of August.
A Note on Variety Success
PomPon dahlias are very vigorous and root easily.
Ball dahlias are very vigorous and root easily, while Giant Dinnerplate varieties may take a little more time and care.
If a cutting doesn't take, don't be discouraged. It is often just a matter of the stem being too woody or the humidity being a little too low. Part of the joy of gardening is the trial and error. Since you are taking these cuttings from plants you already own, there is no financial risk—only the potential for a more beautiful garden.
Conclusion
Taking dahlia cuttings in summer is one of the most practical and satisfying skills a gardener can learn. It turns a routine task like pinching or pruning into an opportunity for growth and abundance. By understanding the simple needs of a young stem—shade, humidity, and a little bit of warmth—you can easily double or triple your collection of these stunning summer favorites. For more dahlia basics, see All About Dahlias.
At Longfield Gardens, we love helping you find ways to make your garden even more spectacular. Whether you are starting with our premium tubers in the spring or propagating your own "bonus" plants in the summer, the goal is always the same: a yard filled with color and life. For more options, browse our Dahlia Collections.
Final Tips for Success:
- Always use clean, sharp tools to prevent the spread of disease.
- Focus on early-to-mid summer for the best chance of tuber development.
- Keep humidity high and light indirect until you see new growth.
- Be patient; some varieties just need a little extra time to find their feet.
Give it a try this summer. You might find that your favorite new plant is the one you grew yourself from a simple green snip.
FAQ
Can I root dahlia cuttings in just a glass of water?
While some gardeners have success rooting dahlias in water, it is generally less reliable than using a potting medium. Roots grown in water are often more fragile and have a harder time adjusting to soil later on. For the best results, use a well-draining potting mix or perlite, which provides both the moisture and the oxygen that new roots need to thrive.
Do I really need rooting hormone for summer cuttings?
Rooting hormone is not strictly necessary, as dahlias naturally contain hormones that encourage root growth, especially at the leaf nodes. However, using a rooting powder or gel can act as an "insurance policy." it speeds up the process and often leads to a more robust root system, which is particularly helpful if you are taking cuttings later in the summer.
Will a summer cutting produce a tuber for next year?
Yes, most summer cuttings taken before August will develop a small tuber or a clump of tubers by the time frost arrives. While these tubers will be smaller than those from a plant grown all season, they are usually perfectly viable. Just be sure to dig them up carefully and store them in a cool, dry place over the winter. For more background on tuber anatomy, see Dahlia Tubers: What You Need to Know.
Why did my dahlia cutting turn black at the bottom?
If a cutting turns black and mushy at the base, it is likely due to a fungal issue called "damping off." This happens when the soil is too wet, the temperature is too low, or there isn't enough airflow. To prevent this, ensure your potting mix is damp but not saturated, and make sure your tools and pots are clean before you start. If you suspect a pest or disease problem, Common Dahlia Pests and Diseases can help you identify the issue.