Rooted Dahlia Cuttings: How to: Part 2
In Part 1 we talked about all the supplies we need- Now that you have all those things gathered (you did that right??)- Let’s get started!
Tubers potted up in a tray
So we need to generate some cuttings to root. Begin by potting up your tubers. You want to leave the crown area exposed (that’s the top part where the eyes on the tuber are). If you aren’t sure where the crown is- it’s right above the skinny part of the tuber- that’s the neck. The three parts of the tuber are the body (the fat or long part), the neck (usually skinner than the rest of the tuber) and the crown (this is the part that attaches to the stem).
Remember you can use potting soil, sand, soilless medium, perlite- whatever you want to try- it just needs to be able to hold water so you get the tuber moist. It’s going to take a minimum of 2-3 weeks to “wake up” a tuber. Sometimes longer— remember that varieties that bloom later, take longer to wake up. They can be stubborn and take 2 months occasionally. So take this time into account in regards to when you want to plant out. It will also take 3-4 weeks to root your cutting.
3-5 weeks wake up time (average) + 3-5 weeks root time + 1-2 weeks to harden off = successful rooted cutting ready to plant. (add another 4 weeks if you like to pot up to a larger container after rooting) Take that time and back it up from your last frost date and you’ll know when to start.
Now- this is the point where people start asking for tubers to ship early because they realize they are suddenly “behind!” Actually, think of it like this- it’s much less stressful. Don’t worry about trying to make a ton of new plants off new to you varieties in their first year. Just plant the tuber or rooted cutting (whatever you bought)- grow it and evaluate it. Then you can make plans to expand it the next year. I find this method works really well if you are in a hot/extreme climate. You don’t want to waste time multiplying a variety if it doesn’t work well in your climate. So (like I mentioned in part 1)— patience is a big part of this process. You’ll thank yourself in the long run for taking the slow route!
You’ll need to keep your potted tubers warm- you can do this via heat mat or a heated room. If you use a heat mat, make sure you have temperature control. I’ve found too often that I end up rotting tubers this way. I switched to using a heated room a few years ago and I find that it’s a much more even heat and works better. A small closet might work for this.
After a few weeks, you’ll begin to see green sprouts. Once the sprouts are about an inch and a half long, you are ready to “pull” as we say in dahlia lingo.
Prepare your rooting medium (see part 1 for options) and wet it down. You don’t want it sopping wet. Wet enough where it’s not going to dry out for a few days. This level of moisture is going to be a bit different for everyone because of different environments so experiment a bit. After you have prepared your tray you are ready to take your first cutting. You want to firmly grab the sprout at the base right before where it attaches to the tuber, then wiggle it a bit and it will pop off. If a bit of the tuber comes off too- that’s okay. Insert the cutting into your rooting medium (if you are using a rooting hormone, this is the point where you dip it in there). Make sure the cutting is stuck in at least 1/2”- you can go deeper if it’s a taller cutting.
The cutting looks small but I’ve found that taking them at a younger stage works better- I’ve achieved more consistent results this way. Now continue taking anymore cuttings that are ready to pull. After this, place a humidity dome over top of the tray. You want to keep the humidity high during this time. Then place under lights and on top of a heat mat or in a heated room under lights.
Check your cuttings once a day to make sure they aren’t drying out. After about 2 weeks, gently pull on the cutting and see if you feel any resistance. You can also look under the bottom of your tray/pot and see if you see any roots. Once you’ve got roots, you can lift off the humidity dome. Keep growing under the lights (and on the heat mat or in heated room) for another few weeks. Once you’ve got a good root system you can either pot up into a larger container and grow on or harden off and plant outside if you are past your last frost date.
Once your potted tubers start producing cuttings, you’ll need to check every few days to see if there are more ready to pull. Once you pull the first one off, the tuber will usually produce 2 or more for the next round. This is how they multiply quickly.
Remember that rooting cuttings is all about environment so if you fail the first time, make some adjustments— try a new medium, adjust your temperature up or down. Water less or maybe more- Each environment is different so there’s no 100% full proof method (no matter what anyone says)- Each environment has external factors that are out of your control so you have to adjust around those. Keep trying- Dahlias are a great plant to teach propagation techniques. You’ll have it figured out quickly!
