How to Divide Dahlia Tubers in the Spring

Did you know that dividing your dahlia tubers every year has many benefits? I’ll show you my process for dividing dahlia tubers in the spring and explain the advantages of splitting these dahlia root clumps annually.

If you’re looking to get the most beautiful flowers and best results from your dahlia plants next year, dividing your dahlia bulbs every year is essential.

Dahlias are one of my favorite cut flowers in the garden. There are so many different varieties offering the most vibrant colors and unique shapes and sizes.

They may be late bloomers, but once they do, your dahlias will be the last flower standing in your garden until the first hard frost.

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I’m a self-taught hobby gardener, not a Master Gardener. Everything I share with you on my blog is my opinion and things that worked for me along the way.

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What are Dahlia Tubers and Why Should You Divide Them?

Dahlias are perennial plants that grow from tuberous roots and are easily propagated by digging them up and dividing the tubers.

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Plant Health

Dividing dahlia tubers can help keep the plant healthy. As tubers age, they can become diseased or infected with pests.

By dividing the tubers, you can remove any damaged or diseased portion of the tuber, helping to prevent disease.

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Improved Growth

Dividing dahlia tubers can also help to improve plant growth. When tubers are left undivided for too long, they can become crowded, which can result in stunted growth and reduced flowering.

Dividing the tubers will provide more space for the plant to grow and develop.

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Propagation

Dividing dahlia tubers is an easy way to propagate new plants. Each tuber section can be planted separately to produce a new plant.

This can be a cost-effective way to increase your dahlia collection or to share your plants with others.

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Size Control

Dividing dahlia tubers can also be useful for controlling the size of the plant.

If you have a large dahlia plant that is taking up to much space in your garden, you can divide the tubers to create smaller plants.

Renewal

Dividing dahlia tubers can help to renew older plants. As dahlia plants age, they can become less productive and less vigorous.

Dividing the tubers and replanting them can help to rejuvenate the plant and promote new growth.

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When to Divide Dahlia Tubers and If You Should Overwinter Them

The right time to divide tubers is really a personal preference.

Whether you dig up your dahlia tubers for winter or leave them in the ground ultimately depends on what hardiness zone your garden is in.

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Colder Climates: Hardiness Zones 3-7

If you live in colder climates, you will need to dig up the dahlia tubers from your garden beds in the late summer or fall, before the first freeze of the season.

If they’re left in the ground, the tubers risk the chance of rotting and freezing in the winter.

Read more about overwintering dahlias in this blog post about how to dig up and store dahlia tubers HERE.

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You can choose to divide the dahlia roots just before storing the tubers for winter, or you can divide them in the spring.

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Warmer Climates: Hardiness Zones 8-11

In warmer, more mild climates, you have the choice of leaving your dahlia tubers in the ground throughout the winter season or digging them up in the fall and storing them in a cool dry place for winter.

I am in hardiness zone 8b so I personally keep my dahlia tubers in the ground under a layer of mulch that protects them throughout the winter.

I’ve tested both methods and the benefits of leaving the dahlia tubers in my garden beds outweighed the risk for me. It was so much easier to wait to dig and divide the tubers in the spring.

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Dividing Dahlias in the Spring

If you’re uncertain when you should divide dahlia bulbs, take into consideration your last frost date. You can find out information about USDA hardiness zones HERE.

The best time to divide dahlia tubers is in the early spring or when the risk of a hard frost has passed. This is when the eyes on the tuber are more visible. Sometimes if the timing is right you will even see sprouts where the eyes are, making the process that much easier.

It’s also a good time to discard any rotted or diseased tubers that haven’t made it through the winter.

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How to Divide Dahlia Tubers in Spring

In this section, you’ll learn which supplies you need in order to divide your dahlia tubers. I’ll also share the process of how to dig up, divide, and plant your dahlia bulbs this spring.

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Supplies You Will Need for Dividing Dahlia Tubers

To divide dahlia tubers you will need the right cutting tools such as clean pruners and a spading fork, shovel, or trowel. You’ll also need a tarp, buckets, and possibly a wheelbarrow.

• Clean pruners and/or sharp knife
• Spading fork, shovel, or trowel
• Tarp
• Buckets and or a wheelbarrow

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Digging Up Dahlia Tubers

When digging the dahlia tubers out of the ground, the most important thing is to lift the clumps of roots carefully to try to prevent any damage to them.

If you do break a tuber apart there’s most likely a viable eye on one of the other tubers, so don’t worry about it too much.

Start by using the right tool, such as a pitchfork or shovel and gently dig around the large clump and pull up with last year’s stock if possible.

If you’re having trouble getting the clump of dahlias out of the ground, rock a shovel or pitchfork back and forth until you can finally lift the clump out of the ground.

After digging up the tubers, wash off excess dirt before dividing them. Store them in a cool dry place like a potting shed or garage for a few days to allow them to dry.

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How to Divide Large Clumps of Dahlia Tubers

Once the dahlia clumps have dried, you can start splitting them. Dividing the clumps in half will make them easier to work with. It’s really up to you whether to divide the sections even smaller, or into individual tubers.

Every tuber must have an eye in order to be viable. Before an eye sprouts from a tuber, it will look more like a tiny bump. They’re basically where the stem comes from the following year.

Use sharp, clean pruners or a knife when cutting your root clumps. Using clean tools will help to prevent passing any diseases to the tubers.

Examine each dahlia tuber to see how they made it through the winter. Cut these tubers out of the root clump:

• The mother tuber because it’s already expended most of its energy. These offshoots usually have white or pink dots around the base of the stem rather than the typical growth eyes.

• Any damaged, rotted, or diseased tubers.
• Tubers that are small or with skinny necks and no eyes.

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Planting Dahlia Tubers

Dig a hole 4-6 inches deep and lay the tuber horizontally on its side, with the eye facing up. Space the tubers between 12-18 inches. Fill the hole with soil and press down to remove any air bubbles.

Don’t water your newly planted tubers until you see the first green shoots coming up through the ground. Watering before any new growth is visible can cause the tubers to rot.

Consistently water your dahlia plants through the growing season. After your dahlias are established, you should water your plants deeply 2-3 times a week for at least 30 minutes. I have a drip system that works really well.

Slugs and snails LOVE dahlias so as soon as you see new growth popping out of the ground, you must use some sort of slug prevention. I use Sluggo which is safe for pets. I can’t tell you how many times I have had slugs eat the plant as it was just starting out.

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Common Questions About Dividing Dahlia Tubers

Q: What Happens if You Don’t Divide Dahlias?

The dahlia clump of tubers will become too large. The dahlia’s energy is spread too thin among too many stems causing the plant to produce fewer flowers with less vibrant blooms.

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Q: How Often Should You Divide Dahlia Tubers?

In general, dahlias should be divided every two to three years, depending on the size of the plant and the growing conditions.

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Dividing dahlia tubers every year is the best way to ensure you get the most beautiful flowers. By following this process you will keep your dahlia plants healthy.

Be sure to leave me a comment with any questions.

Until next time,

Happy Gardening!

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More Garden Posts for You

How to Safely Dig Up and Store Your Dahlia Tubers During the Winter Season

How to Grow and Care for Dahlias

Cut Flower Garden Dos and Don’ts for Beginners

How to Support Garden Flowers to Keep Them From Falling Over

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