How to Propagate Dahlias From Cuttings in 7 Easy Steps
Are you trying to boost your garden stock of dahlia flowers this season? One of the simplest ways of doing this is through cuttings. In this article, gardening expert and cut flower farm owner Taylor Sievers walks through how to increase your dahlia stock, using your own cuttings.
Dahlias are one of the most well-loved flowers I’ve come across in my time as a flower farmer. They are prized by both growers and home gardeners alike for their beautiful blooms in all sorts of colors, shapes, and sizes. Their beauty makes all the work of digging tubers in the fall worth it. As a cut flower farmer, this is one of my most asked-about flowers by my customers.
Though the tubers can get expensive, there are some ways you can asexually propagate your favorite varieties at home to increase your dahlia stock. The first, and I’ll say the most common way, is by division of the tuber clumps after digging in the fall. This can be rather cumbersome and time-consuming, but it is relatively easy to do once you know how to identify buds on the tubers.
But let’s say you only have only one tuber, not a clump to divide. Can you propagate from one tuber? Absolutely! Read on for steps on how to increase your dahlia stock by cuttings!
How To Successfully Take Dahlia Cuttings
Dahlias can be propagated by either shoot cuttings or terminal cuttings. Terminal cuttings are those that are taken from the tip end of a stem, and thus they are usually taken when the plant is much larger. However, if you’d like to propagate dahlias by cuttings, your best bet is to take shoot cuttings in early Spring.
I like to start this process in early March. Because my last frost date isn’t until late April, most companies will not ship plants until after my estimated last frost date for my area.
However, you can usually request a ship date from the company you are purchasing from. This allows you time to take 1 to 3 cuttings from your tubers before planting out in the field well after your last estimated frost date. You can do this regardless of the variety of dahlia you are growing.
So, without further ado, here are some step-by-step instructions for propagating dahlias by shoot cuttings:
Step 1: “Wake Up” the Dahlia Tuber
Dahlias have starchy potato-like tubers (actually, potatoes themselves are tubers) that grow and multiply beneath the surface of the soil during the growing season.
When you order or purchase dahlia tubers, they will usually come individually rather than in a large clump with multiple tubers. The supplier will have already done the difficult task of dividing the tuber before they shipped to you, and these individual tubers are much easier to pot up early in the season.
You’ll need to fill a small pot with moist, well-draining potting mix and plant the tuber with the “neck” sticking up. The neck is the slender part of the tuber that ends with a sliver of the original root system where the buds or “eyes” are located. A viable tuber will have at least 1 to 2 eyes.
Plant the bulk of the tuber into the pot. Again, keep the neck sticking out so that the eyes are visible and easy to access.
Step 2: Wait While Providing Adequate Light and Moisture
Once you’ve planted your tubers (necks sticking up!), you’ll need to place them in a moderately warm area (about 50 to 60⁰F) with light. After about 2 weeks, you’ll notice some new shoot growth coming from the bud(s).
Keep these shoots in a sunny window to make sure they don’t become etiolated. Etiolation is when small seedlings or shoots become leggy and stretched and they are often pale in color. This is due to a lack of sufficient light. You may also choose to add supplemental lighting if you don’t have a sunny south-facing window.
Make sure the potting mix stays moist but not saturated. You can put the pots on a heat mat to help jumpstart shoot growth.
You’ll need to wait until the shoots have about two sets of leaves and are at least 2 to 3 inches long before it is time to take your first cutting!
Step 3: Prep Your Pots and Work Area
When the shoots have reached the adequate size, prepare the pots or trays that you are going to use for your cuttings. There are a few ways to do this.
First off, make sure your pots or trays have been washed thoroughly and sanitized. You don’t want any harmful microorganisms infecting your baby dahlias!
Fill your cell tray or pot with ideally clean or sterile loose potting mix or seed-starting mix. The media should be well-draining and loose, but make sure to tamp down the mix when filling the pot or tray so there are no air pockets.
Next, use a dibble or a pencil to poke holes for your cuttings in the potting mix. Now you’re ready to take a cutting!
Step 4: Use a Sharp, Clean Knife to Slice Off a Cutting
Select a clean, sharp knife to take your cutting. You don’t want to risk any chance of infection by potential plant pathogens, both for your cutting’s sake and your tuber’s sake. Dahlia tubers can cost a pretty penny, after all!
Note where the shoot meets the tuber. You want to make a clean cut at the base of this shoot. Some gardeners will say take a portion of the tuber also, while others will say avoid this due to possible damage of the tuber. I opt for somewhere in between. When I make a cutting, there is usually the tiniest sliver of grayish-brown tuber tissue at the base of the shoot.
Make sure you sanitize your knife in between each cutting you take! I usually wipe my knife down with a cotton ball soaked in isopropyl alcohol after each cutting I take.
Step 5: Pull Off the Lower Leaves on the Dahlia Shoot
Leaves are essential for photosynthesis, but they are also plant tissue that needs to be maintained by the plant. As such, they require energy.
We don’t want most of the energy a plant produces to go to tip growth when the plant has no roots. We need roots! So, we opt to remove some of the foliage for a time so that the plant can focus on root growth.
Step 6: Dip Your Cutting in Rooting Hormone
While not mandatory, the use of rooting hormone will help give your cuttings a jumpstart on root growth, which is ultimately what you need in order to plant these baby dahlias outside eventually.
Rooting hormones can be purchased as liquids or powders. Typically you can find the powdered form at garden centers. Propagators like to use rooting hormone because it helps accelerate root initiation, shrinks the amount of time for ample root production, and sometimes can increase the amount of roots compared to lack of rooting hormone use.
Step 7: Plant Your Cutting!
Place your cutting in the holes of your potting mix that you previously made with a dibble. Press the soil in around the cutting firmly to ensure there are no air pockets and that the cutting is held in place securely.
Humidity and light are very important at this stage. Make sure to keep the cuttings moist, but not saturated. You can do this by periodically misting the leaves and the surface of the potting mix. Keep the cuttings in a humid environment at 65 to 72⁰F for 2 to 4 weeks.
Usually roots will develop within the first 14 days. You may choose to put the pots on a heat mat also.
Also, for adequate root growth to develop, your dahlias will need longer day lengths. Because dahlias love the sun, it’s suggested by the American Dahlia Society that you provide light for at least 14 hours per day. You can achieve this by adding supplemental lighting.
I have had success with using LED shop lights plugged into a power strip with a timer on it so I don’t have to worry about turning the light on and off. Fluorescent shop lights are also inexpensive and easy to set up. Both of these shop lights come with hooks and chains for easy hanging from a shelf.
After a few weeks, you can gently tug on your cuttings or carefully pop them out of the pot to see if they have adequate root growth for planting out. If you can see several healthy roots twining throughout the pot and it is after your last estimated frost, you are ready to start the process of hardening off your cuttings! Expose them to natural sunlight slowly over a week and then plant them out in your garden or in a patio pot.
Congratulations! You’ve propagated dahlias by cuttings successfully! You can usually take a few more cuttings from each tuber after your initial cutting. I am more conservative and typically only take two cuttings per tuber per season, but there are some growers that will take 5 to 7 cuttings off of each “mother” tuber!
Whenever you propagate a plant, you’ll almost always run into a few unexpected snags along the way. Here are some of the most common problems you may encounter when trying to plant new dahlias from cuttings in your garden.
My Cutting Wilted Almost Immediately
There are a few reasons that this could happen, but the most common is that the environment was not humid enough and so the plant loses turgor pressure and wilts. About a day before I’m ready to take my first cutting, I gently water my dahlia tubers in their pots. I want the shoot to be nice and hydrated.
When I plant my cutting into its pot or cell tray, I make sure that the potting mix is moist. Remember, you don’t want it to be saturated, but definitely make sure the mix is very moist.
After I plant my cutting, I will often mist it with a spray bottle. As long as the potting mix appears moist, I don’t usually have to water the cutting for several days. If I notice the cutting starting to wilt or turn yellow but the potting mix is still moist, I will mist the leaves with a spray bottle immediately. If the potting mix appears dry, I will gently water the pot.
My Cutting Turned Black at The Base and Died
This is likely due to something called damping off. Damping-off is caused by root rot organisms that will infect a new seedling or plant and plug the vascular system, causing the plant to wilt and die.
The most important step to prevent damping off is to make sure you are using clean pots or trays, a clean knife, and a sterile potting mix.
Some gardeners like to mix up their own potting mix and they use compost, which inherently is not sterile. This is often thought of as a good thing, but I wouldn’t recommend it for propagating cuttings.
Basically, the main point is, don’t go collect soil from your garden and use it in your pots. There are a lot of microorganisms in garden soil and compost, and some of them are harmful to your baby plants. Also, peat or coconut-coir based potting mixes are looser than soil so they help promote root growth in pots.
My Cutting Didn’t Develop Roots
Unfortunately, sometimes this happens. Some people will attribute this to insufficient light, some will say that this is why you should use rooting hormone if you didn’t, and still others will say they really don’t know why this happens.
This is a good reason why you would want to take more than one cutting from each tuber, just in case one fails due to this reason or disease or other factors.
Even if the cutting puts on one or two stray roots eventually, I would not waste the garden space by planting it out in the garden later on. It is likely that it will struggle and may not become large enough to bloom that season. Focus on the plants that are thriving, not struggling!
If you’ve made it through this article, then rest assured you have the steps to be successful with dahlia cuttings–I promise! It’s always fun to practice propagation by cuttings, and if you are keeping your space and tools clean and providing all the necessary factors, you will likely have success! Learning the skill of taking cuttings will make purchasing those highly sought after dahlia varieties worth it for your garden!