If you grew dahlias recently for the first time, you probably are wondering what to do with them during the winter or how to divide them so you have even more plants next year! Dahlias are an easy-to-grow plant that rewards gardeners with more and more tubers each year resulting in more blooms and more plants. But it's important to know what you are looking for when you divide.
The Anatomy of a Dahlia Tuber
Many plants produce either bulbs, corms, seeds, or tubers. Dahlias produce tubers, that kind of look like a potato. Tubers are the underground storage structures that fuel a new plant’s growth each season. For a dahlia tuber to produce a viable plant the following year, it must include all of these parts:
Eye: This is the growing point, and it looks like a small bump or bud on the crown of the tuber, usually located near where it was attached to the previous year’s stem. The eye is essential for sprouting; without it, the tuber will not grow.
Neck and Crown: This narrow part of the tuber connects the body to the eye. A healthy neck is crucial because if it is damaged or broken, the eye will be unable to access nutrients from the tuber, preventing sprouting. The crown is the larger portion of plant material at the end of the neck where the tuber was attached to the mother tuber or plant stalk.
Body: This is the main part of the tuber, which stores nutrients. It provides the energy the plant needs to begin growing in spring. A tuber without an eye will not grow, but one without a full body won’t have the resources it needs to sustain growth.
For successful planting, make sure each tuber you plan to plant has a firm body, an intact neck, and at least one visible eye. Size really doesn't matter though. Anything bigger than a AA battery should do great! So don't toss the little ones.
Dividing Dahlia Tubers
Timing: The best time to divide dahlia tubers is in late fall after the first frost has blackened the foliage, or in early spring before planting. In fall, allow the tubers to cure for a few days after digging them up so the skin toughens and they’re easier to handle. I prefer to divide in spring when the plant has started to wake up and the eye is more visible.
Preparation: Start by cleaning off excess soil with your hands or a soft brush to expose the tuber clump. Then use a garden hose on a gentle setting to wash away any remaining soil. Avoid using high pressure to prevent damaging the tubers or breaking the delicate necks, which are critical for a viable tuber.
After washing, let the tubers dry for about 24 hours on a non-concrete surface, such as a wooden table, a tarp, or in ventilated crates. Concrete or garage floors should be avoided as they can pull moisture from the tubers, increasing the risk of dehydration. Giving the tubers time to dry is important for toughening the skin, making the tubers easier to handle and helping to prevent rot during storage.
Remember to handle the tubers carefully to avoid damaging the necks, as a broken neck makes a tuber nonviable.
Identifying Eyes: Look carefully for eyes on each tuber; they are small growth points that appear as tiny bumps near where the tuber attaches to the main stem (known as the “crown”). Eyes are easiest to spot after the tubers have been exposed to light for a few days, so if they’re hard to see right away, give the clump some time. I like to run my finger over the neck and crown of the tuber since I can sometimes feel an eye before I can see it. Some varieties produce more eyes than others and earlier than others. So if you don't see any eyes, just store the clump for a little longer and try again later.
Dividing the Clump:
Using a sharp, sterile knife or pruners, start by cutting away individual tubers from the central stem.
Ensure that each division includes at least one eye, an intact neck, and a firm body. My first year dividing, I just cut off at the necks. I lost entire varieties this way! Ensure there is a crown with an eye at the end of each neck.
Avoid tubers with no eyes, as they will not sprout, and discard any that feel soft or show signs of rot.
If eyes are difficult to locate, try cutting into smaller sections of the clump and then dividing further once eyes are more visible.
Inspecting and Preparing Divisions:
Check each divided tuber for any signs of damage or disease. Trim off any damaged areas. You can cut into a tuber if it has rot on the end. Simply cut back until there is no more brown inside the tuber. Allow cut tubers to draw for another day or two before storing.
Let the divided tubers cure in a cool, dry area for a few days to allow cut surfaces to callous, which helps protect them from disease.
Storage: If dividing in the fall, store your tubers in a cool, dry, frost-free place over the winter. Place them in slightly damp peat moss, vermiculite, or sawdust to prevent rot or mold. Check after a few days, then weekly, then every few weeks to ensure they are not drying out or developing mold.
With these steps, each healthy tuber with a visible eye and intact neck will be ready to produce a beautiful dahlia plant that is an exact duplicate of the mother plant next season. Dividing dahlias not only increases your collection but also contributes to healthier plants and more blooms!
If you would like to add more dahlias to your collection, check out our varieties here at Peak Bloom or sign up for our email list to be notified when we restock.
Happy Growing!