How to Plant Dahlia Tubers

Learn how to plant Dahlia tubers in the ground to fill your gardens with beautiful blooms from mid-summer through fall.

Dahlias are easy plants to grow and yield beautiful flowers from mid-summer through fall.

Planting Dahlia tubers in the ground is relatively easy, but there are a few things to know on how to grow dahlias.

I’ll walk you through how to plant dahlia tubers in this post and show you how easy they are to grow so that your garden will be as stunning and lush as possible this summer with beautiful dahlia flowers.

How to Plant Dahlia Tubers in the Ground

I fell in love with growing dahlias several years ago. They are one of the easiest cut flowers to grow in the cutting garden and yield outstanding results.

In my early years of growing dahlias, I made several mistakes that resulted in rotted tubers or poor producing blooms.

Luckily, through trial and error and research, I have learned what works for planting dahlia tubers.

These tips have improved my success rate, and now I can grow the large dinner plate varieties (my favorites) without fail each spring.

Here are a few things you should know on how to grow dahlias from tubers and succeed with dahlias from the start.

What Are Dahlias?

Dahlias are bushy, flowering plants with tuberous roots originating in Mexico, Central America, and Colombia. Dahlia flowers have different colors and often vary from white, pink, yellow, orange, and red.

Dahlias are well known for their large prolific flower production and varied flower petals. They are a perfect cut flower because they have a long vase life and come in such beautiful colors.

Dahlias come in different sizes, ranging from petite 2-inch pompoms to huge 15-inch dinner plate blooms.

Are Dahlias Perennials?

Dahlias are considered to be tender perennials. You’ll need to determine your hardiness zone to know if they are either annual or perennial plants, according to your plant zone hardiness.

In USDA hardiness zones eight and up, they can be grown as perennials, while in zones seven and below, they must be grown as annuals.

When grown as annuals, the tubers must be dug each year and stored until the following spring.

How to Store Dahlia Tubers Before Planting

Dahlias are shipped as tubers. The tubers are grown, harvested, and then stored before being shipped in time for the growing season.

If you don’t have the opportunity to plant dahlia tubers immediately, keep them stored in their original bag in a dark, cool place until the growing conditions are right for planting.

Dahlia tubers should be kept around 40-45 degrees, ensuring they stay dry and have good air circulation.

You can also opt to sprout dahlia tubers early in pots to get a head start on the growing season. For all those details, check out my post, Sprouting Dahlia Tubers Early in Pots!

Ordering Dahlia Tubers to Plant

When your dahlia tubers arrive through mail order, you may notice different dahlia varieties have distinctive characteristics. Dahlias are all different in terms of shape and form.

There is no set standard for tubers of various types. Tubers come in many different shapes and sizes. Some might have long, skinny tubers, while others have short, fat ones.

When to Plant Dahlia Tubers in the Ground

The best time to plant dahlia tubers is in the spring after the last frost date has passed. Dahlia tubers should be planted between mid-April and early June, depending on the region that you live in.

A good rule of thumb for planting dahlia tubers is to plant them when you would plant tomatoes and to stop planting them around mid-June.

You can use the USDA Hardiness Zone Finder to see what the average frost and growing zones are for your area. Generally, it’s safe to plant dahlias around this time.

Of course, if there are any forecasted late frosts, it’s advisable to wait for these to pass before planting out. It is typically recommended to wait at least two weeks after the last frost before properly planting tubers in the garden beds.

Dahlia tubers should be planted once the ground temperature is at least 60 degrees. If you plant too early, your tubers may rot in the ground.

Dahlias need warm, well-drained soil, and you should avoid planting them in areas where the soil will remain cold and wet for extended periods.

One way to achieve blooms early is to start dahlias indoors about a month before planting. You will have a head start on the growing process by starting dahlia tubers in pots.

You’ll have tubers with new growth ready to put in the ground once the soil warms to 60 degrees.

Where to Plant Dahlia Tubers

Dahlia tubers should be planted in a site with optimal sun exposure that receives at least 6-8 hours of full sun each day if you are planting tubers in a hot climate, plant them in a location where the dahlias will have morning sun and afternoon shade.

Knowing where to plant your dahlia tubers is essential for helping your flowers thrive. Dahlias grow best in fertile, rich, well-drained, loosened soil.

Slightly acidic soil with a pH level of around 6.5 to 7 is ideal for growing beautiful dahlias.

How Deep to Plant Dahlia Tubers

Dahlias should be planted where the plant’s crown (where the tuber connects to the main stem) is at a depth of 3-4 inches of soil.

Dig the planting hole and place the tuber with the eye or stem facing upwards. Gently cover up the dahlia tuber with soil.

How Far Apart to Plant Dahlia Tubers

Small and medium-sized dahlia varieties should be planted at least 12-18 inches apart, while larger dahlia varieties should be spaced 18-24″ apart.

Before planting, ensure the space between the tubers has been measured. Dahlias are more likely to have a pest or fungal problems, such as powdery mildew, if there is a lack of airflow between the plants.

What Month Do You Plant Dahlia Tubers

Dahlia tubers are generally planted from mid-April to mid-May but no later than mid-June. The most important thing to remember is that tubers should be planted in late spring when soil temperatures have warmed to 60 degrees, and the risk of frost has passed.

Gardening Essentials You May Need

Wooden Stake: These wooden stakes are made of untreated pine, and with a chiseled end, they are easily put into the ground. They are strong enough to support the dahlias as they grow.
Garden Twine: this garden twine spool prevents tangles and, with a hole in the lid, helps to dispense the twine easily.
Bone Meal: bone meal naturally promotes the healthy growth of dahlia tubers and plants.
Sluggo Plus: if you are looking for an off-the-shelf product to deter slugs and snails, Sluggo Plus, is a great option.
Floral Preservative: extend the vase life of cut dahlia flowers by using a floral preservative.

How to Plant Dahlia Tubers in the Ground

Dahlias are excellent flowers to plant in your garden because they are beautiful and easy to grow. They come in various colours and sizes, from small tubers to large ones. They may also come in single tuber form or as a clump of tubers.

Whether growing shorter varieties or tall dahlias, there is a dahlia flower for everyone. Here is a good guideline on how to plant dahlias in the ground.

Step 1: Choose the Location

Dahlias are sun lovers that need hours of direct sunlight to flourish. To get the most out of your dahlia, plant the tubers in a location that gets at least 6 hours of sunlight per day.

Step 2: Prepare the Soil

When planting your dahlia tubers, begin by loosening the soil and digging a 4-6″ deep hole. Once you dig the hole, add a small amount of organic matter to the hole, including bone meal, aged manure, or garden compost. This will help to provide important nourishment for growing dahlias.

Dahlias will grow best in loose, fertile, well-draining soil. Avoid planting dahlia tubers in areas with soggy and compacted soil.

If you have heavy clay soil, amend it with sand or peat moss to lighten the soil and help it drain.

If your soil is sandy, you may need to add compost. Spending time to amend the soil will produce healthier plants with more flowers.

Step 3: Provide Support

If you are planting tall varieties of dahlias, you will need to provide some support for them. Dahlias have hollow stems and may break in windy or rainy conditions.

Putting the stakes in the ground before planting the dahlia tuber will ensure that you don’t damage the tuber.

To support dahlias, use a metal or wooden stake around 60″ long. Drive it into the ground 8-12″ deep.

As the stems grow, tie them to the stake every few feet to provide solid support for the plant to grow.

Step 4: Plant

Place the dahlia tuber on its side several inches deep with the eye on the tuber facing upward. Then, cover with soil. Firm the soil but do not water the tuber.

Step 5: Label

Before planting the tuber in the ground, write the name of the variety on the back of each stake. This helps to remember what has been planted and what to write on the tubers when dug up at the end of the growing season in the fall.

It is also vital to have labels if you expect to divide and sell tubers. Another option for labels is to use hanging slate weatherproof garden labels.

Step 6: Water

Dahlias do not need to be watered until after they have sprouted. I recommend planting dahlia tubers after spring rain when the ground is slightly damp, as this will help get the tubers growing. However, too much water will cause the dahlia tuber to rot in the ground.

Dahlia plants should get their first set of leaves before you regularly water them. You should then water them 2-3 times per week, preferably deep watering with a long soak using a drip line.

Drip irrigation is ideal, as it directs moisture to the roots while keeping the foliage dry.

Step 7: Fertilize

To fertilize dahlias, wait until the plant has at least three to four inches of new shoots before applying fertilizer. Organic fertilizer can be applied every 30-45 days, but no fertilization should be applied after the end of August.

Believe it or not, I use coffee grounds to fertilize my dahlias. Every 30-45 days, spread ¼” dried coffee grounds on the surface and gently work it into the top of the soil.

The coffee grounds left behind in your coffee pot after you brew coffee are a great source of fertilizer. They provide about 2% nitrogen, a third percent of phosphoric acid, and roughly 1% of potassium.

You can use them to fertilize your dahlia garden or cut flowers. It’s a free and sustainable way to keep your garden healthy and beautiful all season long.

If you choose to use organic fertilizer, go for one that is low in nitrogen and high in potassium and phosphorus.

Do not over-fertilize with nitrogen, or you risk having a bushier plant with small or no blooms, weak tuber clumps, or rot.

Step 8: Avoid Pests

Slugs and snails are a common problem for dahlia growers. These pests can cause significant damage to the plant, but with a line of defense in place, it is possible to avoid some of the issues.

I prefer to use an organic approach in my gardening. Sprinkling coffee grounds or broken eggs shells around the base of the Dahlia plant can help keep slugs at bay. If you want an off-the-shelf, easy solution to use, many growers use Sluggo Plus.

how long do dahlia tubers take to sprout

Tubers don’t sprout until they have been in the ground for at least 4 to 6 weeks; some varieties may take up to 8 weeks.

This is why I prefer to start my dahlia tubers in pots, that way, I know I am planting a viable dahlia tuber. Once the soil warms to 60 degrees, I transplant the actively growing tuber into the garden.

When Do Dahlias Bloom

Dahlias typically bloom about 8 weeks after planting, depending on the variety, usually by late July. By mid-August and September, the dahlia garden is in full bloom.

How Long Do Dahlias Bloom

Dahlias can bloom around four to five months if you’re attentive in taking care of them. With regular deadheading, dahlias will flower from July until October or whenever you get your first frost.

Do You Soak Dahlia Tubers Before Planting

I do not soak my dahlia tubers before planting. Some people do; however, one of the concerns that might arise is that they would be more at risk of tuber rot. Once a dahlia tuber is planted in the ground, it will rehydrate in the soil.

how Late Can You Plant Dahlia Tubers

To ensure the best results for your dahlia bulbs, you should plant them between mid-April and early June, depending on your regions last frost date. It is best to avoid planting dahlia tubers after mid-June.

Do Dahlia Tubers Come Back Every year

For those in a cold climate (below hardiness zone 8), dahlias will not be able to return annually as they cannot endure freezing temperatures.

On the other hand, in places with mild winters, the dahlia tubers can be left in the soil to overwinter and will bloom again in the following season.

Quick Overview Guide to Planting Dahlias

Here is a summary of the key steps for planting dahlia tubers in the ground.

Start your dahlias early. You can plant dahlia tubers in pots to get a jump start on the season. Once the soil warms to 60 degrees, transplant them into the garden.
Choose a sunny location, as Dahlias bloom best when they get a lot of good light from the sun.
Amend your garden for the best start to growing healthy Dahlias. Compost and rotted manure are both great options to add to the soil.
Add bone meal when planting the tubers. This will provide important nourishment for your growing dahlia plant, as dahlias are heavy feeders.
Position the tuber with the stem facing upwards.
Avoid watering the dahlia tubers until the young plants have their first set of leaves. If you live in an extremely hot and dry climate, it would be okay to water the dahlia tubers lightly when you plant them in the ground.
Fertilize the dahlias when they are about 8-10 inches tall. Then continue to fertilize every 30-45 days until the end of August.
Pinching dahlias when they are about 10″ tall will produce a bushier plant with more flowers. For step-by-step instructions, be sure to visit HERE!
Disbud dahlias for maximum size blooms. Learn how HERE!
Enjoy the blooms by harvesting blooms for a vase life of 5 to 7 days from stems cut at the proper stage. Harvest dahlias early in the morning when they are almost fully open. Be sure to use a floral preservative in the water to prolong blooms.

More Dahlia Flower Gardening Tips and Ideas

Learning how to plant dahlia tubers properly will get your gorgeous dahlias off to a great start. It can be a bit of work to place in the garden stakes and add amendments to the soil, but it is always worth it.