Are you unsure of what or where the eye is on a dahlia tuber? Do you have a tuber with small eyes that are hard to spot?
Identifying eyes on a dahlia tuber proves that it is able to grow. Ideally, dahlia tubers should also be planted with their eyes facing up. However, sometimes these eyes are pretty hard to spot. Learn how to identify dahlia tuber eyes below.
Dahlias are beautiful summer-blooming flowers that brighten up any garden with their vibrant colors. While they are commonly referred to as having bulbs, dahlias actually grow from tubers – which can often cause confusion about what dahlia bulbs look like.
The truth is there’s no such thing as a dahlia bulb! The potato-like structures we plant to grow dahlias are tubers not bulbs. This is an important distinction when learning how to grow and care for dahlias.
In this article, we’ll cover everything you need to know about dahlia tubers, including:
- What is the difference between tubers and bulbs?
- What do dahlia tubers look like?
- Size, shape and viability of tubers
- The parts of a dahlia tuber
- How to split and divide tubers
- And more!
Let’s start by understanding the key differences between bulbs and tubers.
Dahlia Tubers vs Bulbs – What’s the Difference?
Though often confused bulbs and tubers are structurally different
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Bulbs are made up of modified leaf scales surrounding a central disc that houses the embryo flower. Examples are tulips, daffodils, onions.
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Tubers are enlarged stems that function as storage organs. Dahlia tubers are swollen roots that store energy for the plant.
Other key differences:
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Bulbs have distinct layers and grow from a basal plate. Tubers are composed of unstructured, undifferentiated tissue.
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Bulbs produce small bulblets or offsets around the parent bulb. Tubers do not produce offsets, but simply get larger each year.
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Bulbs go dormant after flowering Tuberous roots of dahlias function year-round
What Do Dahlia Tubers Look Like?
Now that we know dahlias grow from tubers, not bulbs, what do dahlia tubers actually look like?
Dahlia tubers resemble irregularly shaped potatoes and can vary greatly in size, shape and appearance. They are often brownish-pink in color, with a cluster of “eyes” on the crown, which is the upper part of the tuber.
Some key characteristics:
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Size: Very variable. Can be tiny like a fingernail or as large as a small potato.
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Shape: Round, oblong, finger-shaped. Variable by variety.
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Color: Varies from light pinkish-brown to dark brownish-red. Generally lighter at the crown.
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Eyes: Cluster of small bumps on the crown which sprout new shoots.
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Roots: Small hairy feeder roots emerging from bottom end of tuber.
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Scars: Scars from old stems may be visible on sides of tuber.
Here’s a photo showing a typical dahlia tuber:
A dahlia tuber with crown, eyes, roots and scars labeled. Photo Credit: Gardening Step by Step
As you can see, the tuber resembles an irregular potato with multiple growing points on the top (crown). The roots emerge from the bottom to take up water and nutrients.
Next, we’ll look at tuber size and viability…
Dahlia Tuber Size and Viability
Dahlia tubers can vary greatly in size depending on the variety and age of the plant. But size doesn’t necessarily indicate viability. Even tiny tubers can grow into full plants under the right conditions.
Here are some tips for assessing tuber size and viability:
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Minimum size: Aim for tubers at least the size of a fingernail. The smaller the tuber, the fewer blooms it may produce in year 1.
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Don’t worry about size: There’s no such thing as a tuber that’s “too small” – even tiny tubers can grow into mature plants. Focus on the overall health of the tuber.
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Bigger isn’t always better: Very large tubers may bloom poorly. The plant focuses energy on the tuber rather than establishing.
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Assess viability carefully: Look for mold, rotting, dehydration. Damage isn’t always fatal – trim off any dead parts.
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Give borderline tubers a chance: Plant questionable tubers in spring to see if they grow. You may be surprised!
Here’s a photo showing a range of viable tuber sizes, from tiny to large:
A range of viable dahlia tuber sizes compared to batteries. Photo Credit: Summer Dreams Farm.
As you can see, tuber size and shape can vary quite a bit. Focus on finding the healthiest tubers rather than the largest. Now let’s look at the key structures of a dahlia tuber…
Parts of a Dahlia Tuber
A dahlia tuber has 3 main parts:
- Crown – Upper portion where eyes/shoots develop
- Neck – Middle constricted portion that attaches crown to tuber
- Tuber – Enlarged bottom portion that stores nutrients
Here’s a diagram of a tuber’s structures:
The 3 main structures of a dahlia tuber. Photo Credit: Summer Dreams Farm
The crown contains meristematic tissue that can develop new shoots and stems. The neck connects the crown to the main body of the tuber. The tuber stores nutrients and energy to power new growth.
Let’s look more closely at the role of each part:
The Crown
- Location of eyes or growth buds
- New shoots develop from the crown
- Must be present for tuber to be viable
- Needs 1 cm2 minimum of crown tissue
The Neck
- Connective tissue between crown and tuber
- Transports nutrients between crown and tuber
- If broken, the tuber will not be viable
The Tuber
- Swollen stem that stores carbohydrates and nutrients
- Provides energy for new growth until plant is established
- Can vary greatly in size and shape
Now that we understand tuber structures, let’s look at splitting and dividing tubers for propagation…
Splitting and Dividing Dahlia Tubers
To propagate dahlias from tubers, you’ll need to split or divide the tubers into smaller sections. Here are some key tips for successful splitting:
When to Divide Tubers
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Spring – Divide just before planting
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Fall – Divide tubers as you dig them up after first frost
What You’ll Need
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Clean knife or pruners
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Dusting sulfur (optional)
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Container of dry potting mix
Step-by-Step Process
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Carefully wash tubers to remove soil. Remove any damaged/rotten tubers.
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Find the crown and identify the main tuber. Remove small, broken off pieces with no crown.
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Make your first cut vertically through the main tuber and crown to split into 2-3 chunks.
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Further divide chunks, slicing through neck of tuber but leaving 1 cm2 crown attached.
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Dust cuts with sulfur powder to prevent rotting.
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Plant tuber chunks in potting mix, or store for winter in dry medium.
Here’s a visual guide to splitting dahlia tubers:
Step-by-step process for dividing dahlia tubers. Photo Credit: Summer Dreams Farm.
The key is making clean cuts through the tubers while retaining a piece of viable crown on each section. This will yield multiple new tubers.
Caring for Dahlia Tubers
Once divided, tubers need proper care to remain healthy:
During Growing Season
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Plant in well-draining soil in full sun
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Water 1-2″ per week; avoid overwatering
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Stake tall varieties
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Deadhead spent blooms
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Mulch for consistent soil moisture and to reduce rot
After First Frost
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Cut back foliage and dig up tubers
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Allow to dry for a few days
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Remove excess soil, trim any damage
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Dust with sulfur powder
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Store tubers in cool, dry medium like vermiculite or peat moss
Proper harvesting, drying, and storage of tubers will keep them healthy from season to season.
Key Takeaways
- Dahlias grow from tubers, not bulbs
- Tubers resemble small, irregular potatoes
- Size doesn’t determine viability – look for overall health
- A tuber needs some crown tissue to be viable
- Divide tubers in spring or fall, retaining crown tissue
- Store tubers in cool, dry conditions over winter
Size doesn’t Matter (mostly)
One common concern people have when they receive a dahlia tuber is, ‘This is so small. Will this produce a quality dahlia plant?”
When it comes to tubers, size doesn’t matter – to a point. Let’s step back for a second and ask, what is a dahlia tuber? A dahlia tuber is a tuberous root of a dahlia plant. It is a starchy body that contains food, water, and nutrition for a dahlia plant to grow until it establishes a root system that will then provide food for the plant.
As long a dahlia tuber is large enough to accomplish what I described above, it is big enough. So how big is that? When I am training new employees, I explain to them I want a tuber to be at least the size of my little finger (about the size of a AAA battery). Tubers smaller than that will produce a plant but it might not produce as many flowers. It should create quality tubers that can be divided for the following year. When I am shipping out tubers, regardless of the variety, I try to make sure the smallest tubers anyone receives are the size of a AA battery. Keep in mind that a tuber that is skinnier than I described is still OK if it is longer. The battery measure is more about total volume of the tuber than the thickness or length.
Representative examples of the variety of shapes and sizes dahlia tubers come in. AA battery for size reference. 1. Peaches n’ Cream 2. Blyton Softer Gleam 3. Bonanza 4. Cafe au Lait 5. Hamari Gold
In the photo above, you can see the variety of shapes and forms different tuber come in. These are all examples of quality tubers I wouldn’t question planting in my garden or on my farm. If I had to pick a perfect size tuber, I would want it to be around the size of the two Bonanza examples (#3 in the above photo). I want to stress that not all varieties will produce tubers that are that shape or size, nor do they need to be that size or shape to produce a high quality plant.
I also want to add that there is such a thing as “too big”. If a dahlia tuber is too large, it could actually backfire on it’s ability to produce more quality tubers or develop a large root system. You can think of it as the dahlia sitting on a reservoir of so much food and water that it doesn’t need to seek out more. The top of the plant might have been productive but when you dig these in the fall you can find a single mother tuber without any new tubers. How big is too big? In general, I don’t like it if they are too much bigger than your average size coffee mug.
Keep in mind if the plant normally produces many large tubers, like Ferncliff Copper for example, it is OK if the tubers you plant are larger. If you are concerned about a tuber being too large, you can cut a portion of the back half off the tuber to help promote more root growth.
Another common question I see on various flower forums is, “My tubers dried out in storage. Will these make it?”
Dahlias are survivors. I am always shocked each year when I go out to the compost pile in late June and find tons of dahlias growing out of what I thought to be a pile of trash. While they have a will to live, there are still basic things to look out for. Since a picture is worth a thousand words, I decided to go through my tuber storage and find some examples to show you.
In the photo below, you will see a tubers ranging from perfect with no desiccation (#1) to completely dried out with no hope (#7 – #9). In my field, I will plant anything that looks like #1 – #4 without any hesitation. Each of those will produce a quality plant. With #5 and #6, it is a little more debatable. #5 has an eye actively growing but as you will see in the next photos, that does not guarantee it is viable.
Various states of desiccated dahlia tubers
In the two photos below, you see the same tubers. The first photo shows what the exterior of the tubers looks like and the second shows what the inside of those same tubers looks like after they were cut in half. When you handle a tuber, you can feel if there is any moisture left in it. Although #1 looks really shirred, it was still malleable and you could feel there was moisture inside of it. The same was true for #3, even though it looks arguably worse than #2. Although #2 had a viable eye on it, the tuber than held all the plants energy was completely dried out and would not have been able to support that eye. There was no hope for #4 and looking inside of it confirmed this. In the examples below, I would have planted #1 and #3 in my field but not #2 or #4.
In short, when you are looking at dahlias that seem dried out, it does not mean they will not be viable. You can tell by the feel of the tuber if there is still moisture inside and as long as they are not dried out, they will be fine.
Examples of dried tubers. Look at the next photo too see what they look like inside.
Examples #1 and #3 both still have white flesh inside, while #2 and #4 are completely dehydrated and brown. The black under the tuber are rocks I used to prop them up for the photo.
This is for the most part common sense, but I will talk about tuber rot for a moment. If you have a rotten tuber, it won’t grow.
What causes tuber rot? It can be fungal or bacterial. Normally it enters from a cut that was made when you lift or split, from excessive moisture on the tuber, or rot travelling down the stem of the plant into the tuber clump. It will first look brown or black and then travel deeper into the tuber.
When you find rot on your tuber, cut it away until you find only clean, white flesh within the tuber. If you find rot all the way into the neck of the tuber, it is not going to be viable. If you find rot all through the crown attached to that tuber, it is not going to be viable. Sometimes it takes a bit of dahlia surgery, but if you can remove all of the rot, the tuber should be fine.
Below is an example of a dahlia tuber that is not viable due to rot. From the outside it looked fine, but when I picked it up, I felt a soft spot and immediately knew it was not going to be viable since the neck of the tuber was rotten.
It is common to see a little mold growing on the cut ends of a dahlia tuber. A small amount of mold is OK as long as it is superficial and not entering the dahlia tuber and causing rot. You can normally squeeze the end of the tuber and tell if the rot has traveled into it.
An example of some mold growing on the cut end of a dahlia. In cases where there is only a little mold present as in this photo, it normally does not impact the viability of the tuber.
Dahlia Tuber and Splitting Guide
With spring right around the corner and things warming up, I thought it would be a great time to start something I have wanted to do for a while: start a blog. I am hoping for this to be a casual thing, mostly talking about tips and tricks for growing or different happenings here on the farm. What a better way to to kick it off than with a review on dahlia tubers?!
Over the last five years we have split over 200,000 dahlias on our farm. At this point for us it is just muscle memory but for others it can be a real challenge. Questions about splitting and storing dahlia tubers are probably the most common I receive and seem to be what people struggle with the most when it comes to these beautiful flowers. In this post I am going to concentrate on the tubers themselves rather than on their storage. If you are interested in how to store tubers, make sure you check out our Dahlia Care page for some good information on that.
Just like people, different dahlia varieties have unique characteristics and come in many different shapes and sizes. Some might have long and skinny tubers, where others are short and fat. Some might produce lots of tubers per clump, and others might only be practical to propagate from cuttings because they produce few, if any viable tubers. Some store well, while others are notoriously difficult to store without them rotting or dehydrating. In short, when working with mother nature, you cannot look at tubers as an ‘off the shelf’ widget. Each one will be unique and there is no ‘standard’ shape or form for dahlia tubers across different varieties.
Here are some examples of different dahlia clumps that I pulled out of storage before they were split. This is what they look like when we put them into storage. There is still soil on them and they are not cleaned up too much yet.
A typical clump of Rip City dahlia tubers. It is one of the most productive varieties we grow.
A little better than average clump of Sweet Nathalie dahlia tubers.
A clump of Sea Nugget dahlia tubers. The tubers are on the smaller side but a clump like this can easily split 5 or 6 times.
How to Plant Dahlia Tubers From Start to Finish
FAQ
What should dahlia bulbs look like?
To grow a healthy dahlia, it’s important to start with a tuber that has an “eye” (or growth bud) on the crown of the stem. A tuber without an eye won’t grow a plant, and tubers should be firm, with no signs of mold or rot.
What is the difference between dahlia tubers and dahlia bulbs?
Dahlia tubers are sometimes called a “bulb”, but they are technically a tuber, similar to a potato. Similar to a potato, the tuber sends up a shoot that becomes the plant, which produces leaves and flowers. Underground, the tubers multiply each year (again, like a potato).
Which way is up on a dahlia bulb?
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Identify the “eyes”:Look for small, raised areas, tiny buds, or pinkish/reddish spots on the crown (where the stem connected to the tuber).
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Plant with eyes facing up:Place the tuber in the soil with the “eyes” facing upwards, as this is where the new stems and flowers will emerge.
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Plant on their side:Place the tuber on its side with the eyes facing up.
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Planting depth:Dig a hole 4 to 6 inches deep and place the tuber on its side, with the growing eye facing up.
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Spacing:Allow at least 12 inches (30 cm) of space between plants, as dahlias can get quite large.
What does a dead dahlia bulb look like?
If your dahlia tubers are mushy, they’re most likely dead. If they’re shriveled up, there’s a chance they’re still alive.