Growing dahlias this year? Unleash a summer explosion of blooms with this beginner’s guide to planting dahlia tubers. Learn the secrets to HUGE, healthy flowers that will steal the show.

Dreaming of a summer garden bursting with vibrant and unique blooms? Look no further than the dahlia! If you are diving into the world of dahlias for the first time, this means you’ll likely start growing them by planting their tubers.

Dahlia tubers pack a punch with their impressive size and range of colors, guaranteed to turn heads in your garden. But before you can witness their beauty, planting dahlia tubers takes a little TLC.

This beginner’s guide will walk you through the process, from prepping the perfect spot to tucking in your tubers for a season of stunning blooms.

Learn how to plant dahlia tubers with these simple tips.

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About Planting Dahlia Tubers

Because dahlias are tender perennials, you can’t plant the tubers until all danger of frost has passed. Which for me this year is April 27.

Because the hardiness zone map changed, your last frost date likely changed too, so make sure you check it before planting. This year, I’m able to get my dahlia flowers in much sooner than prior years.

Where to Buy Dahlia Tubers

You’ll most likely be shopping for dahlia tubers instead of full-grown plants. I love to scroll through the vibrant selections from trustworthy online nurseries. I usually order my dahlia bulbs online from reputable sources like Longfield Gardens and White Flower Farm to find the prettiest and most unique flowers.

Local nurseries can surprise you with gems but typically have a more limited selection. So I recommend you shop online.

Regardless of where you purchase them, it’s important to select healthy dahlia tubers that are plump, firm, and free from any signs of decay, mold, or damage. Choose tubers that have “eyes,” which are small buds or growth points on the tubers that will eventually sprout into stems and leaves.

Dahlias look best when planted in groupings. I usually go with at least three dahlia plants per variety and include a few different varieties in the same area of my garden. And if you lack growing space, yes you can grow dahlias in containers too.

dahlia tubers after getting hosed off - Overwintering Dahlias
Dahlia tubers after getting hosed off

How to Plant Dahlia Tubers

Planting dahlia tubers is a pretty straightforward process. But did you know there is a right and a wrong way to plant the tubers? Yes! Learn how to properly plant dahlia tubers and avoid the pitfalls with these simple tips.

  • Select a spot in your garden that receives at least 6-8 hours of direct sun with well-drained soil. Dahlias love to grow in loamy, fertile soil with good drainage and are not fans of heavy clay soils. You can also amend the soil with organic matter, such as compost, or well-rotted manure, to improve its drainage and fertility. It’s also a good idea to add some leaf mold to help with moisture retention.
  • When planting dahlia bulbs, dig a hole that is about 4-6 inches deep and wide enough to accommodate the tuber.
  • Place the dahlia tuber with the “eyes” facing upwards in the hole and cover it with soil. If you are planting several tubers, space them about 18-24 inches apart to allow for proper growth and airflow.
  • When you are finished planting, water the tubers well.
penhill watermelon dahlias

When to Plant Dahlia Bulbs

The perfect time to plant dahlias is a bit of a dance with nature, largely depending on your local climate. Post-frost, when the soil warms to about 60°F, is generally your green light. If you want to have a good gauge on the soil temperature, you’ll need to use a soil thermometer .

This usually means late spring to early summer for most gardeners. For those in gardening zones 7 and up, mid-April to early May is ideal, while zones 6 and below might wait until May or early June depending on your climate. With global warming, these dates have been trending earlier, so make sure you check your last frost date for the best planting time for your locality.

Eager to get going? You can start your dahlias in containers in a protected spot without watering them, just letting them wake up naturally. When the time’s right and the outdoor soil is warm, they’re ready to make their move to the garden stage.

dahlia flowers in the potager garden as we prepare for fall planting

Planting Dahlia Tubers FAQs

Do you soak tubers before planting?

I do not soak dahlia tubers before planting, but it can be helpful if your tubers look a bit shriveled or dry. Soaking them before planting is a bit like giving the tubers a pep talk before the big game. It’s not mandatory, but soaking them in water for an hour or two before planting can rehydrate them, giving them a nice boost of energy to kickstart their growth once they’re in the soil.

Fill a bucket or sink with cool water and let your tubers have a little spa moment, making sure not to leave them in too long, as over-soaking can lead to rot. After their quick soak, plant them as you normally would. This little extra step can encourage quicker sprouting and give your dahlias a strong start to their growing season.

Again, I’ve not needed to do this because the tubers I’ve purchased or overwintered look plump and healthy before planting, but I know a few gardeners that soak them.

dahlia fleurel and labrynth in the cut flower garden
Dahlia Fleurel and Labrynth

What month do you plant dahlia tubers?

The perfect month to plant dahlia tubers depends on your local climate and the risk of frost in your area. Dahlias are warm-weather lovers and can’t withstand frost, so the golden rule is to plant them after all danger of frost has passed and the soil has warmed up.

For most gardeners, this sweet spot tends to be in the late spring to early summer. Here’s a quick guide based on USDA Hardiness Zones:

  • Zones 7 and above: These areas enjoy milder winters, so you can generally start planting dahlia tubers in mid April to early May.
  • Zones 6 and below: In these cooler regions, where winters can be more severe, it’s safer to wait until May or even early June to plant.

A handy tip is to use a soil thermometer to check the soil temperature. Dahlias like it cozy, with soil temperatures around 60°F or higher being ideal for planting.

If you’re itching to get a head start or if your region has a shorter growing season, consider potting your dahlia tubers in containers indoors, placing them in a warm, sheltered spot. Just hold off on watering until you’re ready to move them outside, which helps prevent rot and encourages strong, healthy growth once they’re planted in their final outdoor spots.

Last year, we had such a mild winter here in my zone 6b garden, that I planted my dahlia tubers much earlier than I should have. Because temperatures were very warm and there was no nightly frost predicted, I planted my dahlias in my newly raised garden beds in mid-April.

That said, I was prepared to protect them with a frost blanket if we had a last-minute frost or freeze. But that never came so I got my dahlia flowers off to an early start here.

dahlia kogane fubuki in the potager garden
Dahlia Kogane Fubuki

How deep do you plant dahlia tubers?

When planting dahlia tubers, aim to tuck them into the soil about 4 to 6 inches deep. This depth provides enough coverage for the tubers to stay snug and protected while also allowing the emerging shoots to reach the surface without too much trouble.

Planting dahlias too deeply can hinder their growth in a couple of ways:

  • Struggle to sprout: Dahlias send their shoots upwards from the “eyes” on the tubers. If buried too deep, these sprouts may not have enough energy to push through a thick layer of soil, delaying emergence and weakening the plant.
  • Reduced stem and flower development: Deep planting can affect the soil temperature around the tubers. Dahlias prefer warm soil for optimal growth. Burying them deeper keeps them cooler, potentially slowing down stem and flower development.
dahlia fleurel in the potager garden by fountain
Dahlia Fleurel

Do you fertlize dahla tubers when planting?

The quality of your soil will determine if and when to fertilize dahlia tubers after planting. If you add a soil amendment like aged manure, fertilizer is not needed when you plant. However, if composted materials like pine bark, leaf mold, peat moss, or something similar are used, then add about 1/4 cup of balanced fertilizer per plant.

You don’t need to apply a high-strength fertilizer right at planting time as it’s better to focus on the quality of your soil. Organic matter not only feeds your dahlias but also improves soil structure and drainage, creating an ideal environment for tuber development.

However, the first month after planting, I recommend using a slow-release fertilizer so the application is set and forget and will make things easier for you during the remainder of the growing season. Always follow the manufacturer’s instructions for application rates.

Look for a fertilizer with an N-P-K ratio (nitrogen-phosphorus-potassium) that supports root development and overall plant health, such as a 5-10-10 or 10-20-20 formulation. The key is to encourage strong root growth without promoting too much early leaf growth, which can be achieved with a fertilizer higher in phosphorus than nitrogen.

Avoid high-nitrogen fertilizers at planting time, as they can promote foliage growth at the expense of flowers. Once your dahlias are established and start to show growth, you can switch to a more balanced fertilizer to support both foliage and bloom development throughout the growing season.

Remember, moderation is key with fertilizers; too much can harm your plants. More is not better!

dahlia cafe au lait at sunrise
Cafe Au Lait Dahlia Flower

Do you water dahlia tubers after planting?

Figuring out the watering needs of your dahlias can vary quite a bit based on your local growing conditions. Initially, your soil’s natural moisture is often adequate, meaning you might not need to water your dahlias until they showcase their first true leaves. Jumping the gun on watering can lead to soggy conditions that dahlia tubers greatly dislike, potentially causing them to rot. And we don’t want that!

When to Start Watering Your Dahlias

As soon as your dahlias display their first true set of leaves, it’s time to start a more regular watering routine. Aim for a deep soak about 3-4 times a week. I’m a big fan of using drip irrigation for this task—it gives the plants a thorough, gentle soaking.

When I water with a drip line, I let it run for around 30 minutes at a time. During those scorching hot stretches, I increase to daily watering, but always with a cautious eye to ensure the soil isn’t becoming waterlogged. The last thing any of us want is for our precious dahlia tubers to rot from too much love.

Ultimately, you’ll want to strike a good balance. So keep a close eye on both your dahlias and their soil moisture for happy, healthy blooms.

variety of dahlia flowers in a colorful cut flower garden
Different varieties of dahlias in a colorful cut flower garden

More About Planting Dahlia Tubers

Have you planted dahlia tubers before? Do you have any tips you’d like to share? I would love to know more in the comments below.

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garden blogger stacy ling with her dahlias in the cut flower garden

Garden Supplies I Use

Since I’ve been gardening for well over twenty-five years, I’m often asked about the garden supplies and tools that I use most. Here are some of my favorites that I use in no particular order.

dahlia kogane fubuki in the potager garden

Click here to shop my favorite garden supplies!

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variety of vibrant dahlia flowers in a colorful cut flower garden

Small Space Gardening: The All-You-Need Guide to Growing Showstopping Dahlias in Pots

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Thank you so much for following along.

Enjoy a beautiful day! xo

Stacy Ling

Want to learn more about me? I’m a master gardener who’s been gardening and growing things for over 25 years and author of the best-selling book, The Bricks ‘n Blooms Guide to a Beautiful and Easy-Care Flower Garden. Get the inside scoop about my background as a master gardener, education, and experience, as well as why I started blogging here.

stacy ling cutting dahlias in her garden

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2 Comments

  1. I’m getting ready to split my dahlia tubers next month. I can’t wait for dahlia season! You have so many great varieties growing in your garden, Stacy. Beautiful!