With the first day of Spring comes longer days, milder weather, and bulbs pushing up through the soil. If you are choosing to grow dahlias this year it is time to start getting everything ready for planting, which includes checking on your tubers in storage and possibly getting a few shipments of new varieties in the mail. Exciting times indeed!
One of the biggest questions I get at this time of year is, “Will it grow?” In order to answer that question let’s bust some myth’s around dahlia tubers.
Anatomy of a Dahlia Tuber
There are a few key elements that every dahlia tuber needs. The crown, the neck, and the tuber or body. In addition to those three items, your crown needs to have an eye. If you are missing any of these things your plant will not grow.
The tuber body is the plant’s food source that allows the plant to get growing. The crown is the piece that used to be attached to the main stalk of last years’ plant. This is the only place an eye will form. Without the crown (with an eye) your plant will be blind and only be able to grow a root system and not a plant stalk. The neck is the bit that holds the other two together.
What does an eye look like?
The eye (or sprout) of the tuber only grows from the crown of the plant. When dividing your tubers you need to make sure you either see the eyes where the new plant will grow or leave enough crown attached to the tuber to ensure the highest probability of an eye forming. There is no magic formula to this, but it is recommended to leave a crown about the size of a dime attached to the tuber and neck.
I prefer to divide my tubers in the fall after digging, before putting them into storage for the winter. However, there are plenty of people who divide in the spring right before planting. It really depends on how much room you have in storage and how much time you have to devote to this task.
It can take up to 6-8 weeks for some tubers to ‘wake up’ while others wake up in only a couple of weeks. This varies with the tuber variety and the conditions you have them stored in (how warm your room is). The term wake up refers to the tuber forming an eye and starting its active growing season. Because the time frame is so widely varied it is important to not give up on your tubers. They may develop that eye when you least expect it. I have even fished tubers out of the compost pile after chucking them because they started to grow.
Does Size Matter?
The short answer is no…ish. Tubers come in many different sizes and shapes from short and round like golf balls, to long and skinny like a banana or pencil, and everywhere in between. This depends a lot on the variety and growing conditions the plant grew in.
The tuber is the plant’s food source, so it needs to be large enough to sustain growth until it sends roots out and makes more tubers. On the size spectrum, most tubers that are larger than the size of a AAA battery will grow a full-size plant complete with beautiful flowers. So should you seek out larger tubers? Not necessarily. Big fat tubers (larger than a coffee mug) are more likely to rot, plus they tend to signal to the plant that it may not need to produce more tubers or a large root system because the plant has all the food it requires.
In the photo above I would be happy to receive and plant any of these tubers, however, I would prefer to get tubers 2-4 as they are nice and plump and not too big or small.
Can you know what variety it is by looking at the tuber?
No, you cannot know what variety the dahlia is simply by looking at the tuber itself. You will need to employ a serious labeling system and be meticulous when digging and dividing your tubers if you want to keep your names straight. Above is an example of 3 different American Dawn tubers. You can see one is fat with little to no neck. The middle one is a beautiful tuber showing a perfect example of the three different parts of a tuber (Tuber, neck, crown). The third tuber is smaller golf ball-sized with little to no neck. All are examples of viable tubers.
How shriveled is too dried out?
Some drying out or wrinkling doesn’t mean all is lost, but your tuber needs some moisture inside it to be able to grow. The first tuber in the photo above is perfect and looks the same as when I put it in storage in November, while the next three tubers show varying signs of dehydration. Tuber two and three still feel like they have a good amount of moisture in them when you gently squeeze them and as long as they eye up they will produce beautiful plants.
The last tuber you see above is questionable. You can cut the end off the dahlia tuber to check for moisture and viability of the plant. If you see white on the inside of the tuber (you can see an example of this further down in this post) you will know you have a viable plant as long as it produces an eye. On the other hand, if you cut into your tuber and it is brown and shriveled you know this tuber has zero moisture left and can be chucked into your compost.
What if my tuber has a broken neck?
In the photo above there are two tubers attached to a piece of crown, however, the tuber on the left has a broken neck. You can see the stringy bits under the skin of the tuber connecting the crown to the tuber and it is floppy. This neck is too damaged to carry food from the body to support a plant and needs to be cut from the crown to avoid the potential of rotting.
If the skin has peeled off but the neck is still intact or there is only a small hairline fracture your tuber may still be likely to grow.
How do I know if my tuber is rotten?
Sometimes it is painfully obvious when you find a rotten tuber, like in the video above. The tuber looks like a husk with nothing inside or when you pinch the tuber your finger squishes inside it. These tubers cannot be saved and can be put in your compost.
Other times it is more difficult to see if your tuber has any rotten parts. One way to see if there is rotting on the inside is to cut the tuber. You can see in the photo above that I have cut the end off the tuber and see white on the inside. This one is not rotten, you want to see that white flesh inside the tuber. When you see black inside the tuber that is when you know it is starting to rot. Depending on the severity of the rot you may still be able to save the tuber by cutting the rotten parts off.
Using sanitized clippers or garden scissors you can cut the black parts off the healthy part of the tuber. Keep in mind that you will need to keep the tuber larger than a AAA battery like discussed earlier to grow a full plant. Once you perform this minor tuber surgery you can leave the tuber on your table for about 24 hours to allow for the wound to heal over and/or dip the end in cinnamon to help prevent mold growth and seal the wound.
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Every year when I am looking at those iffy tubers I ask myself, “Will this grow?” And because of the miracle of nature, I usually find a few that I have misjudged and have started sprouting in my compost pile. That is all part of the joy of gardening.
I hope this information was helpful for you no matter where you are on your dahlia journey. Feel free to share this post with a friend if you think they would benefit from this information as well.