Table of Contents
- Introduction
- Why Take Dahlia Cuttings in Autumn?
- The Best Time for Fall Cuttings
- Identifying the Right Stems to Cut
- Essential Tools and Supplies
- Step-by-Step Guide to Taking the Cutting
- Managing the Winter "Hold"
- Troubleshooting Common Autumn Cutting Issues
- Moving Cuttings Back to the Garden
- Realistic Expectations for Success
- Conclusion
- FAQ
Introduction
There is nothing quite like the sight of a dahlia garden in full late-summer glory. As the days begin to shorten and the air turns crisp, these plants often find their second wind, producing some of the most vibrant and oversized blooms of the season. It is during this time that many gardeners start thinking about how to keep that beauty going for next year. While most of us are used to digging and storing tubers, you might find yourself wondering if there is a way to get even more plants from the varieties you love without waiting for spring.
At Longfield Gardens, we believe that gardening should be a rewarding and accessible adventure for everyone. Propagating your favorite dahlias through cuttings is a wonderful way to expand your collection and share your most prized varieties with friends. While spring is the traditional time for taking cuttings, doing so in the fall is a clever technique that can help you preserve rare varieties or "sports"—those unexpected, beautiful color mutations that sometimes appear on a single branch.
In this guide, we will explore the practical steps for successfully taking dahlia cuttings in the autumn. You will learn how to identify the best stems, the specific equipment you need for indoor success, and how to keep those baby plants thriving through the winter months. Whether you are a seasoned dahlia grower or a beginner looking to try something new, this method is a simple way to ensure your garden remains full of color year after year. Autumn dahlia cuttings are a practical and effective way to multiply your stock and protect your favorite varieties from winter storage risks.
Why Take Dahlia Cuttings in Autumn?
Most gardeners think of dahlia propagation as a spring chore. In the spring, you wake up your tubers and snip off the new sprouts to create "basal cuttings." However, taking cuttings in the fall serves a different and equally important purpose.
One of the most common reasons to take autumn cuttings is to preserve a specific plant that has shown unique characteristics. Occasionally, a dahlia will produce a "sport." This is a natural genetic mutation where one branch of the plant produces flowers of a different color or form than the rest of the bush. If you wait until you dig the tubers in late fall, you may lose that specific mutation, as the tuber itself usually reverts to the original variety's DNA. Taking a cutting from that specific branch ensures you can grow that exact "sport" next season.
Another benefit of autumn cuttings is insurance. Some dahlia varieties are notorious for having thin, spindly tubers that do not store well over the winter. These varieties often shrivel up or rot before spring arrives. By taking a cutting in September or October, you keep the plant in a "growing" state. While the mother plant goes dormant, your cutting lives on indoors, eventually forming its own small "pot tuber" that is often much easier to keep alive than a large, fragile tuber from the garden.
Finally, autumn cuttings give you a significant head start. By the time May rolls around, a cutting taken in the fall will be a sturdy, well-established plant ready to hit the ground running. This often leads to earlier blooms compared to plants started from tubers in late spring.
The Best Time for Fall Cuttings
Timing is everything when it comes to successful propagation. You want to take your cuttings while the plant is still actively growing and looking healthy. The ideal window is typically four to six weeks before your first expected autumn frost. In most regions, this means late August through September, and your Hardiness Zone Map can help you fine-tune the timing.
During this window, the plant is still full of vigor. The stems are pliable and the sap is flowing well, which helps the cutting develop roots more quickly. If you wait until after a light frost has nipped the foliage, the plant’s internal chemistry begins to shift toward dormancy. Cuttings taken from a plant that has already started to "shut down" for the winter have a much lower success rate.
When choosing a day to take your cuttings, aim for a cool morning. Plants are most hydrated in the early hours of the day. A stem that is plump with water will stay fresh longer while you are working with it, giving it a better chance of survival once it is placed in its rooting medium.
Key Takeaway: Take your dahlia cuttings in late summer or early autumn while the plant is still actively blooming and before the first frost arrives to ensure the highest success rate.
Identifying the Right Stems to Cut
Not every branch on a dahlia bush is a good candidate for a cutting. To ensure your new plant grows strong and healthy, you need to be selective about which parts you remove.
Look for "lateral shoots." These are the smaller side branches that grow out from the main stem, usually at the point where a leaf meets the stem. These side shoots are typically more vigorous and root more easily than the main, thick, hollow stems.
A good cutting should have the following traits:
- Health: The leaves should be deep green with no signs of yellowing, spots, or pests.
- Size: Aim for a shoot that is about 3 to 5 inches long.
- Structure: It should have at least two to three sets of leaves.
- Solid Stems: Dahlias famously have hollow stems, but the very tip of the growth and the area right around the "nodes" (the bumps where leaves grow) are usually solid. Rooting happens best in these solid sections.
Avoid taking cuttings from stems that already have a flower bud at the tip. A plant that is trying to bloom is focusing its energy on reproduction rather than root development. If you must use a stem with a bud, pinch the bud off immediately to redirect the plant's energy downward.
Essential Tools and Supplies
Taking cuttings does not require a laboratory, but having the right supplies on hand makes the process smoother and keeps your plants healthy. Because you are essentially creating an open wound on the plant, cleanliness is your top priority.
Sterile Cutting Tools
Use a very sharp, clean knife or a pair of micro-tip floral snips. Dull blades can crush the stem fibers, making it harder for the plant to take up water and more likely to rot. Before you start, wipe your blades with rubbing alcohol or a 10% bleach solution to prevent the spread of soil-borne diseases.
Rooting Medium
You want a medium that is "sterile" (free of fungi and bacteria) and "well-draining" (water moves through it quickly). Standard garden soil is too heavy and often contains pathogens that will kill a tender cutting. Good options include:
- Seed starting mix: A lightweight blend of peat moss or coco coir and perlite.
- Perlite or Vermiculite: These can be used on their own for rooting, as they provide excellent aeration.
- Rooting cubes: Pre-made sponges or foam cubes designed specifically for propagation.
Small Pots and Domes
Four-inch plastic pots are the perfect size for individual cuttings. You will also need a way to keep the humidity high while the cutting develops roots. You can use a professional humidity dome or simply a clear plastic bag turned upside down over the pot.
Grow Lights
This is the most critical piece of equipment for autumn cuttings. Because the days are getting shorter in the fall, a windowsill will not provide enough light to keep a dahlia cutting alive through the winter. You will need an LED or fluorescent grow light that can be kept on for 14 to 16 hours a day.
Step-by-Step Guide to Taking the Cutting
Once you have gathered your supplies and identified a healthy donor plant, you are ready to begin. Follow these steps for the best results.
1. Make the Cut
Locate your chosen lateral shoot. Using your sterile blade, cut the shoot away from the main plant. Try to cut as close to the main stem as possible, but be careful not to damage the mother plant.
2. Prepare the Stem
Take your 3-to-5-inch cutting back to your workspace. Trim the bottom of the stem so that the cut is clean and just below a "node." The node is the area where the leaves join the stem; this area contains a high concentration of natural growth hormones.
3. Remove Excess Foliage
Strip off the bottom set of leaves. You want at least an inch or two of bare stem to insert into the soil. If the remaining leaves are very large, you can actually cut them in half horizontally. This reduces "transpiration"—the process where the plant loses water through its leaves—and helps the cutting stay hydrated until it has roots.
4. Apply Rooting Hormone (Optional)
While dahlias root fairly easily on their own, a quick dip in rooting hormone (powder or gel) can speed up the process. It also often contains a mild fungicide to protect the fresh cut. Simply dip the bottom half-inch of the stem into the hormone and gently tap off any excess.
5. Plant the Cutting
Use a pencil or a "dibber" to poke a hole in your moistened rooting medium. Insert the stem into the hole, ensuring at least one node is buried below the surface. Gently firm the medium around the stem so there are no air pockets.
6. Create a Humidity Chamber
Place your humidity dome or plastic bag over the pot. This traps moisture and creates a greenhouse-like environment. Place the pot under your grow lights in a warm spot.
What to do next:
- Label your pots immediately with the variety name and the date.
- Place the cuttings in a warm area (65–75°F).
- Keep the light source about 4 to 6 inches above the top of the cuttings.
- Mist the leaves once a day if the environment looks dry.
Managing the Winter "Hold"
The biggest challenge with taking dahlia cuttings in autumn is not the rooting itself, but keeping the plants healthy indoors for several months. Unlike spring cuttings, which go into the garden after a few weeks, autumn cuttings must survive until the following May.
Light Requirements
In nature, dahlias begin to form tubers when the day length drops below 12 hours. If you want your cuttings to keep growing leaves rather than just making a tiny tuber and going dormant, you must trick them. Keep your grow lights on a timer for 14 to 16 hours a day. This "long day" light schedule keeps the plant in a vegetative state.
Temperature Control
Dahlias like a consistent temperature. Avoid placing your cuttings near drafty windows or heating vents. A steady room temperature between 65°F and 72°F is ideal. If your basement or garage is too cold, a seedling heat mat placed under the pots can provide the gentle bottom heat needed to keep the roots active.
Watering and Feeding
Be very careful not to overwater. Because the plants are growing slowly indoors, they do not need as much water as they would in the summer sun. Wait until the top inch of soil feels dry before watering.
Once you see new growth at the top of the cutting (usually after 3 or 4 weeks), you know roots have formed. At this point, you can begin a very diluted feeding schedule. Use a balanced liquid fertilizer at one-quarter strength once every two weeks.
Troubleshooting Common Autumn Cutting Issues
Even with the best care, you may run into a few hurdles. Here is how to handle the most common issues with a positive, proactive approach.
Wilting
It is normal for a cutting to look a little limp for the first 24 to 48 hours. If it remains wilted after that, your humidity might be too low. Check to make sure the dome or bag is sealed well. If the soil is soaking wet and the plant is wilting, it may be a sign of "damping off," a fungal issue. In this case, it is best to start over with a fresh cutting and sterile medium.
Yellowing Leaves
Yellow leaves often indicate either too much water or a lack of light. Ensure your pots have excellent drainage and that your grow lights are close enough to the plants. If the lower leaves turn yellow and fall off while the top stays green, the plant may just be shedding old foliage to focus on new growth—this is usually nothing to worry about.
Powdery Mildew
Because dahlia cuttings need humidity, they can sometimes develop powdery mildew—a white, dusty-looking fungus on the leaves. To prevent this, ensure there is some air circulation. You can lift the humidity dome for an hour a day to let fresh air in. If you see mildew, a gentle spray of one part milk to nine parts water can often clear it up without harsh chemicals.
Pests
Check your plants regularly for aphids or spider mites, which love the warm, dry air of a home in winter. If you spot them, a simple spray of neem oil or insecticidal soap (following the label instructions) will usually take care of the problem.
Moving Cuttings Back to the Garden
As spring approaches, your autumn cuttings will likely be sturdy little plants. Depending on the variety, they may have even started to form small tubers in their pots.
Before planting them outside, you must harden them off. This is the process of gradually acclimating the plants to the outdoor environment. Start by placing them in a sheltered, shady spot for an hour or two a day, gradually increasing their exposure to wind and sun over the course of 7 to 10 days.
Wait until the danger of frost has completely passed and the soil has warmed to at least 60°F before planting them in their permanent garden home. Because these plants already have an established root system, they will often take off much faster than newly planted tubers.
Realistic Expectations for Success
Gardening is a partnership with nature, and results can vary based on your local climate, the specific dahlia variety, and your indoor setup. Some varieties root in 10 days, while others may take three weeks. Some may thrive all winter, while others might struggle with the lower light levels of a home environment.
It is helpful to view autumn cuttings as an "extra" rather than a guaranteed replacement for your tubers. If you take five cuttings and three survive the winter, you have three beautiful, free plants that you wouldn't have had otherwise! This experimental mindset makes the process much more enjoyable. We often find that the most rewarding moments in the garden come from these small experiments that lead to big, colorful payoffs. If you need shipping information for new orders, it is always a good idea to check before you buy.
Key Takeaway: Success with autumn cuttings depends on providing consistent light and warmth throughout the winter. Treat the process as an enjoyable experiment that adds more variety and insurance to your dahlia collection.
Conclusion
Taking dahlia cuttings in autumn is a fantastic skill for any gardener who wants to get the most out of their favorite plants. It allows you to save unique mutations, preserve varieties that are difficult to store, and multiply your garden's beauty at no extra cost. By following a few simple steps—choosing healthy lateral shoots, using sterile tools, and providing consistent indoor light—you can successfully carry your dahlias through the winter months.
At Longfield Gardens, we want you to feel confident in your garden. While there is a bit of a learning curve to overwintering cuttings, the reward of seeing those familiar blooms early next summer makes every bit of effort worthwhile, especially if you love dinnerplate dahlias. Remember that even experienced gardeners lose a cutting now and then; the joy is in the process of learning and growing along with your plants.
- Select healthy, non-blooming lateral shoots before the first frost.
- Use a sterile medium and keep humidity high during the rooting phase.
- Provide 14–16 hours of supplemental light to prevent early dormancy.
- Gradually harden off your established plants before moving them back to the garden in spring.
Taking dahlia cuttings in the fall is one of the best ways to ensure your most loved varieties return year after year, giving you peace of mind and a more beautiful landscape.
If you are ready to expand your collection even further, we invite you to explore our wide selection of decorative dahlias. Growing these stunning flowers is one of life's simple pleasures, and we are here to support you every step of the way.
FAQ
Is it better to take dahlia cuttings in the spring or the autumn?
Both have advantages. Spring cuttings are easier because the plants naturally want to grow as the days get longer, and you don't have to keep them indoors for very long. Autumn cuttings are better for preserving "sports" or color mutations and for ensuring you don't lose varieties that have tubers that are difficult to store over winter. If you want a refresher on the process, see our How to Take Dahlia Cuttings From Plants: A Step-by-Step Guide.
Do I need to use rooting hormone for autumn cuttings?
While not strictly necessary, rooting hormone is highly recommended for autumn cuttings. Because the plant's natural growth cycle is slowing down in the fall, the extra boost from the hormone can help the stem produce roots faster and protect it from rot while it is in the rooting medium.
Why do my autumn cuttings need 16 hours of light?
Dahlias are "short-day" plants when it comes to tuber formation. If they receive less than 12 hours of light, they stop growing leaves and start focusing all their energy on making tubers and going dormant. To keep a cutting growing and green through the winter, you must provide "long-day" conditions (14–16 hours) using grow lights.
Can I root dahlia cuttings in water?
Yes, you can root dahlia cuttings in a glass of clean water. However, the roots that form in water are often more fragile than those grown in a soil-based medium. If you use the water method, be very gentle when transplanting the cutting into soil, and do so as soon as the roots are about an inch long.