Everything You Need to Know About Growing and Caring for Your Garden Dahlias

Do you love the way dahlias look, but are not quite sure about what it takes to grow these beautiful blooms in your own garden? Here’s a guide to everything you need to know about growing and caring for your garden dahlias.

There are so many reasons why dahlias are my favorite flower.

They’re not only available in a rainbow of colors, but there are so many varieties to pick from, with different shapes and sizes. Dahlias take their time to fully bloom, but they are so worth the wait!

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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 personal opinion and things that worked for me along the way.

You’ll find dahlias in my garden, hardiness zone 8b, from mid-summer through the fall’s first freeze. I think what I like best about dahlias is the fact that they peak at a time when other flowers in the garden are starting to die off.

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Growing Dahlias in Different Climates

Dahlias are considered a tender perennial in cold regions of North America. They are only winter hardy in planting zones 8 to 11.

I’m in zone 8B here in the Seattle area, so I’m able to keep my tubers in the ground year-round. However, I make sure to put mulch or mowed up leaves around each plant for added protection during the winter months.

Gardeners in zones 2 to 7 should plant dahlia tubers in the spring, and either treat them as annuals or dig them up and store them through the winter.

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Soil Requirements

Pick a spot in the garden that has well-draining soil, and amend your beds with 2-4 inches of high-quality compost or well-rotted manure, a light dusting of bone meal, and a balanced organic fertilizer.

Mix all ingredients into the soil to distribute evenly.

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When to Plant Dahlia Tubers

Dahlias are cold-sensitive, so it’s best to plant your tubers in the spring after the ground temperature reaches 60°F, and there is no more chance of frost.

To get a head start on the growing season, some gardeners start tubers indoors and in individual containers a month before they would plant them in the ground. I tried this, but for the amount of work it took, I did not see huge results. But that’s just me.

Where to Plant Your Dahlia Tubers

Dahlias require 6-8 hours of full sun a day in order to thrive.

If you’re growing dahlias in the southern part of the country, it’s best to provide afternoon shade from the extreme temperatures.

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How to Plant Dahlia Tubers

Dig a hole 4-6 inches deep and lay the tuber on its side, horizontally, with the growing eye facing up. Fill the hole with soil. Space the tubers in the ground between 12-18 inches.

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Watering Your Dahlias

Wait to water newly planted tubers until after you see the first green shoots coming up through the ground. Watering before any new growth is visible can cause the tubers to rot.

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. You will need to give your dahlia plants more water in hot and dry climates.

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When to Pinch Dahlias and the Benefits

After dahlia plants reach about 1 foot tall, pinch them by snipping out 3-4 inches of the growing center branch. This will encourage bushier plants, as well as increase flower production and overall stem length.

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Pest and Disease Control

Slugs and snails love eating young dahlia plants, and earwigs ruin the flowers. Be sure to put down slug bait, not only after planting the tubers but throughout the season.

There have been times when I’ve forgotten to put slug bait down around my new dahlia plants and the slugs enjoyed eating the entire plant. I use Sluggo, which is an organic option that’s safe for both children and pets.

Every fall I seem to find powdery mildew on my dahlia leaves. You can proactively spray for this from late July to August to prevent this from happening to your leaves.

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Staking Your Dahlia Plants

You will need to stake your dahlia plants when they are a couple of feet tall to keep them from falling over and snapping the stems.

In areas where I have several dahlias planted in a row, I use the corral method. This method involves placing a metal T-post every 8 feet along the outside edges of the beds and stringing a double layer of bailing twine from post to post.

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The Benefits of Deadheading Dahlias

Deadheading is basically removing the spent flower heads.

To get continual flowering throughout the season, deadheading should be done consistently. It prompts the plant to produce more flowers.

Cut back just above the point where the flower stem joins a central stem.

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Harvesting Your Beautiful Dahlia Blooms

The more you cut dahlias, the more your plant will produce blooms.

• Harvest in the early morning, before the heat of the day.
• Place the cut flowers in a bucket of cool water as you are cutting from the garden.
• Remove all leaves from the stems and place the dahlias in a vase of water.
• Use flower food in the water.

Since dahlias don’t open much after being harvested, it’s important to pick them almost fully open, but not overly ripe.

Don’t use a flower for your arrangement if the back of the flower head looks like the petals are browning and dehydrated.

The flowers should last anywhere from 5-7 days if properly taken care of.

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Dahlia Winter Care and Storage

Should You Leave Your Dahlia Tuber in the Ground or Dig Them Up and Store Them for the Winter?

Dahlia plants will blacken after the first fall frost. Once this happens, cut all but 1-4 inches off the plant.

They are hardy to zone 8 and can be cut back and left in the ground to overwinter. I spread mulch or mowed up leaves around the plant to add protection.

In most areas, the winters are too cold to leave the tubers in the ground. For other zones that have colder winters, the tubers should be carefully dug up with a pitchfork or shovel in late fall before the hard frost, and stored through the winter. Be careful not to damage them.

CLICK HERE for more information about overwintering your dahlia tubers.

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Dividing Dahlia Tubers

You should divide dahlia tubers every year because of how quickly they grow. If they get too large, they will rot or become too heavy to lift and store.

Once the tuber clumps have dried, split them in half with sharp pruners so the pieces are easier to work with.

Then you can divide these tubers individually. In order for a tuber to be viable, the eye or eyes must be connected to an unbroken tuber. You can read more about dahlia splitting in my blog post.

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Storing Dahlia Tubers Until Spring

After dividing your tubers, wash the clumps to remove all the excess soil. Dip the clumps into a 5% bleach-95% water solution and lay them out to dry in a cool place, such as a basement or garage for a couple of days.

Once the dahlia tubers are dry, pack them in slightly dampened peat moss or sawdust, and then in a box lined with newspaper.

You can also individually wrap them individually in pieces of plastic cling wrap.

Store them in a well-ventilated, frost-free place, from 40-45º F is ideal, 35-50º. Try to keep the tubers from touching each other, in case one of them rots.

Check tubers monthly throughout the winter, and dispose of any that have started to rot. Read my blog post How to Store Dahlia Tubers During the Winter Months here.

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Dahlia To-Dos in the Spring

I personally leave my tubers in the ground all winter in hardiness zone 8b. Usually, in April, I dig up the dahlia clumps of tubers and split them at that time. You can read more about How to Divide Dahlia Tubers in the Spring here.

If you have stored the tubers for the winter, then you have most likely already divided the tubers before storing them away for the winter.

Remember that each tuber must have at least one eye, or the tuber will not bloom. The eyes are located at the base of the stem and look like little pink bumps.

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I hope you have learned a little something about how to grow and care for dahlias.

This stunning cut flower does take a bit of work such as dividing, storing, and staking. But you will not find a more beautiful flower that produces so many blooms.

Leave a comment below with any other tips or ideas you may have about dahlias. I’d love to hear from you.

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More Gardening Inspiration

An Early Summer Garden Tour

Are you ready for some garden inspiration?

My garden buddy Stacy from Bricks ‘n Blooms is sharing her early summer garden tour in New Jersey. Wait until you see what she’s done in the short amount of time she’s lived in her new home. It’s a little piece of paradise for sure.

Until next time,

Happy Gardening!

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