Dahlia Tuber Parts: Eyes and Crowns

Dahlia Tuber Eyes and Crowns: Understanding What You've Received

You've just received your dahlia tuber from us. It looks like a wrinkly brown carrot, or possibly a small bunch of wrinkly brown carrots. There are no leaves, no shoots, no obvious signs of life. You may be wondering which end is up and whether the thing is even alive.

It is. This guide explains the parts of a dahlia tuber, how to identify the crown and the eyes, and how to tell the top from the bottom. Once you can see what you are looking at, planting and dividing become straightforward.

(Images courtesy of Summer Dreams Farm in Michigan, USA, from their excellent Dahlia Tuber Splitting Guide)

The Parts of a Dahlia Tuber

A dahlia tuber has three parts that matter. The tuber body is the fat, fleshy storage root. It stores the food that powers next year's growth. The neck is the narrow section connecting the tuber body to the crown. And the crown is the knobbly bit at the very top where last year's stems were cut off. This is where everything happens.

The growing points, called eyes, sit on or very close to the crown. They are the dahlia equivalent of potato eyes, except dahlia eyes only appear on the crown, never anywhere else on the tuber body. In spring, each eye swells and produces a new shoot that becomes a flowering stem. A tuber without an eye attached to it will never grow. This is the most important thing to understand about dahlia tubers, and it is the most common mistake when dividing: slicing off a nice fat tuber that has no eye and wondering why it never does anything.

On a dormant tuber, the eyes are still quite easy to spot, rather like a small wart on the crown:

And here is an eye that has started to sprout. The black line marks the point where the neck ends and the crown begins:

How to Find the Eyes on a Dahlia Tuber

Look at the crown. Right at the top, where the old stems were cut, you should see small raised bumps. In early spring, after a few weeks in warmth, these bumps swell visibly and may start to turn pink or green. These are the eyes.

If you have just received your tuber in March and it has been stored cold, the eyes may not be visible yet. They are there. They are just dormant. Place the tuber on a windowsill or in a warm room for a week or two and watch the crown. The eyes will show themselves.

Some tubers arrive with eyes already sprouting, especially if they come later in the season. You might see short pink or green shoots, anything from a few millimetres to a couple of centimetres. These are perfectly fine. Just handle the tuber carefully so you don't snap them off. If one does break, the tuber will produce another shoot from a neighbouring eye. It is a setback, not a disaster.

(Photo used with permission from Clara Joyce Flowers. You can see the round scar where the original shoot was broken off, and the new shoot growing right beside it.)

Which End of a Dahlia Tuber Goes Up?

The crown goes up. The fat end of the tuber body points down. Think of it as a parsnip: the pointy end goes down, the thick end where the leaves were is at the top. Except dahlia tubers often come in clusters, like a bunch of parsnips joined at the top, which makes it less obvious.

Look for the remains of old stems. They are always at the crown, which is the top. If the tuber has visible eyes or sprouts, those are also at the top. Plant with the crown about 10cm below the soil surface.

If you really cannot tell which end is up, plant the tuber on its side. The shoots will find the light. It takes them a little longer, and the stem makes a bend at soil level, but it works. Dahlias are not as fragile as they look in the packet.

What If My Dahlia Tuber Has No Visible Eyes?

If your tuber has just arrived in March and there are no visible eyes, don't panic. Tubers that have been stored cold all winter are dormant. The eyes are there but tiny. Pot the tuber up in a small pot (2–3 litres) of damp compost and keep it somewhere warm and light. A greenhouse, conservatory, or bright windowsill will do. Within two to three weeks you should see swelling at the crown, and shortly after that, green shoots.

If nothing has happened after four weeks in warmth, check that the tuber is firm. Squeeze it gently. If it feels solid, be patient. Some varieties are slow starters. If it feels soft or spongy, it may have rotted internally. Cut the tuber in half. Healthy flesh inside is cream or white. Brown, black, or hollow means the tuber is dead.

Very occasionally a tuber arrives damaged, with the crown broken off. A tuber body without a crown attached will not produce shoots. If this happens, get in touch with us and we will replace it.

Dividing Dahlia Tubers: Why Eyes Matter

Understanding eyes becomes critical when you divide a dahlia clump. After a season in the ground, your single tuber will have multiplied into a clump of several tubers all joined at the crown. Dividing this clump gives you multiple plants for next year. But every division must include at least one eye. A fat tuber with no eye is just a piece of food storage that will sit in the compost and slowly rot.

Wait until March when the eyes are visibly swelling. This makes it much easier to see where to cut. Use a clean, sharp knife. Each division needs one or more eyes on a piece of crown, connected to a tuber body with an intact neck. If the neck is broken and the tuber body is separated from the crown, neither piece is viable.

Let the cut surfaces dry for a day before potting up. Some people dust the cuts with sulphur powder, but we have never found it makes much difference. A clean cut and a day of drying is enough.

For the full division and planting method, see our how to grow dahlias guide. For getting your divided tubers started indoors, read starting dahlia tubers in spring.

Frequently Asked Questions

What does a healthy dahlia tuber look like?

A healthy dahlia tuber is firm, plump, and feels solid when squeezed. The skin may be wrinkled from storage and the colour ranges from pale cream to dark brown depending on the variety. None of that matters. What matters is firmness. If it feels like a potato, it is fine. If it is soft, spongy, or hollow-feeling, it has rotted.

My dahlia tuber has broken. Will it still grow?

It depends where the break is. If a tuber body has snapped off but the crown is intact with eyes still attached, the dahlia will grow perfectly well from the crown. The detached tuber body will not.

In the image above, you can see where the crown meets the necks of the tubers. If you were to cut off all the necks and tuber bodies, the remaining crown would still grow shoots and recover with new tubers for the following year. So if your dahlia got a knock in transit and has a tuber or two hanging by a thread, plant the crown with its remaining tubers as normal. You won't see a noticeable difference in size or flowering.

Inspect any broken-off tuber for a piece of crown with an eye. If you find one, you have two plants. If there is no eye on the detached piece, throw it away. If the crown itself has broken off completely and no eyes remain, the tuber will not grow. Contact us for a replacement if this happens.

Can I plant a dahlia tuber that has already sprouted?

Absolutely. Sprouted tubers often establish faster than dormant ones because they already have active growth. Handle them carefully to avoid snapping the shoots. Plant at the normal depth with the sprouts just below the soil surface so they reach the light quickly. If a shoot does break off, the tuber will produce another from a nearby eye.

How many eyes does a dahlia tuber need?

One is enough. A single eye will produce a single shoot, which branches as it grows and produces a perfectly good plant. More eyes means more shoots and a bushier plant sooner, but one is all you need. When dividing tubers, aim for at least one strong eye per division.

Browse our full range of dahlia tubers. We supply A-grade Dutch-grown tubers that we double-check before dispatch, and every one has a viable crown with healthy eyes ready to grow.