How to Propagate Dahlias from Seed | Gardener’s Path (2024)

I caught the dahlia bug many years ago, but haven’t won the lottery yet so, as much as I’d like to, I can’t fill my garden with piles of new tubers each spring.

So you’d better believe I threw a garden party when I mastered growing dahlias from seed.

For the price of one tuber, I can buy enough seeds to fill up my entire garden with dahlias, and even collect them from my existing plants!

How to Propagate Dahlias from Seed | Gardener’s Path (1)

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Our guide to growing dahlias has all you need to know to cultivate these beautiful flowers in your landscape.

If you want to breed dahlias to create new and unique specimens, growing from seed is a skill you must have.

When you take a cutting or divide a tuber, you’ll grow an exact genetic replica of the parent. But plants started from seed combine the characteristics of both parent plants.

You might end up with something magical and new that no one has seen before. Just imagine the accolades as you share your new dahlias with friends and fellow growers.

And it all started from a little seed. Are you dreaming of growing dahlias on the cheap or producing new types?

Here’s what we’ll go over in this guide so you can make that happen:

What You’ll Learn

  • When to Start
  • Where to Buy Seeds
  • Harvesting Seeds
  • Sowing Seeds

Dahlias grown from seed will develop tubers by the end of the summer.

You can save these and store them over the winter, if you want, or leave them in the ground if you live in the right climate in Zones 8 to 11.

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But, before you can do that, we’ve got to plant those puppies.

When to Start

Dahlias are sensitive to cold temperatures and unless you live somewhere that never freezes, you’ll need to start the seeds indoors before putting them outside when it’s warm enough.

You should start the process of germination a month or two before the last predicted frost date in your area with the idea of planting out a month after the last predicted frost date.

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If you are starting them in a cold basement or your other seedlings tend to take a long time to grow, give them two months. Otherwise, a month should be fine.

You can also direct sow into the garden if you live somewhere warm enough that dahlias can stay in the ground year-round.

This process is less reliable since you don’t have any control over the environmental conditions and herbivores like birds and voles seem to particularly love stealing them.

If you go this route, wait until the soil has warmed to 65°F before sowing.

Where to Buy Seeds

You won’t find seeds for some of the more elaborate dinnerplate dahlias or ball cultivars available, but there are many open-faced (single) or semi-double options out there.

If you aren’t sure what these types are, learn more about dahlia groups in our guide.

For example, Eden Brothers carries the stunning ‘Figaro,’ which has daisy-like flowers in deep purple with sunny yellow centers.

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‘Figaro’

Or, if you want something with a bit more color, consider Unwins Bedding, a mix of a variety of colors also available at Eden Brothers.

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Unwins Bedding

These daisy-like dahlia flowers come in multiple bright colors including white, yellow, orange, red, and pink.

If you’re ready to harvest your own, keep reading.

Harvesting Seeds

As mentioned, dahlias started in this way won’t grow true, which means they won’t look exactly like the plant you collected the seeds from.

If you want an exact replica, you need to grow from tubers.

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Dahlias are octoploids, which means they have four more sets of chromosomes than most flowering plants.

This provides incredible genetic diversity, but it also makes it extremely challenging to predict what plants grown from seed will look like.

You can try to cross two plants you love and hope the traits you desire will appear, but you can’t be sure. It’s a hit-and-miss process.

If you want to try crossing two plants, you will first need to cover your chosen receptive flowers in mesh or nylon bags to prevent natural pollination.

Then, when the dahlia flowers have fully opened and pollen has developed on the stamens, take the pollen from an open flower using a toothpick. Types with large, full heads make it a bit more difficult for you (and other) pollinators to find the pollen.

You might need to pluck some of the petals away from the center of the flower to find the pollen.

Rub this pollen on the stigmas of your chosen flowers. You’ll find the pods on the inside of the blossoms, but they aren’t ready until the blooms have aged and faded.

This happens in the fall for most types. Leave the blossoms on the plant until the first freeze is on the horizon.

Keep the blossoms covered in mesh bags to prevent birds from making off with your seeds.

To harvest the heads, cut the spent flower head away from the dahlia stem and gently rub the pods in your hand to release the seeds inside.

Some pods might be empty and some might have heaps. Set them on a towel or baking sheet to allow them to dry.

Once they feel totally dry, put the seeds in jars or envelopes and place them in a cool, dry area to store them until sowing time in the late winter or early spring.

Some may not be viable, but there’s no way to really know until you sow them and wait for them to germinate. I always sow more than I think I’ll need to compensate for any duds.

Sowing Seeds

To start, fill a tray with seed starting mix. You can also use potting soil, but don’t use one that contains fertilizer.

A seed starting mix is made without soil for a light, airy, water-retentive substrate that supports germination and growth without becoming oversaturated.

Arbico Organics carries an excellent product called Tank’s Pro-Lite Seeding & Potting Mix. It’s available in 16-quart bags.

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Tank’s Pro-Lite Seeding & Potting Mix

Moisten the soil and then gently sprinkle the seeds on top. Place a thin layer of the medium over them and gently press down on the surface of the soil with your hands.

Set the containers on a heat mat set to maintain temperatures of 70 to 80°F and don’t panic if you don’t see any seedlings for a few weeks.

Dahlias aren’t in a hurry to pop up but that doesn’t mean they won’t.

Your setup should be near a window with bright, indirect light as the seedlings will require light as soon as they emerge. You don’t want any direct sunlight at first, though.

If you’d like to, you can cover the tray with plastic or glass to help the soil retain water. Whether you go this route or not, keep the soil moist but not wet – it should feel like a well-wrung-out sponge at all times.

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As the seedlings emerge, you’ll eventually want to thin them out so they are about four to six inches apart. But, because the seeds tend to germinate sporadically,wait until the majority of the seeds have sprouted. I generally wait a month before thinning.

When the seedlings are about six inches tall and all risk of frost has passed, you can transplant them outdoors after a period of hardening off.

To harden them off, take the whole tray outside and set it in a sunny spot that’s protected from the wind for about an hour. Then bring it indoors. The next day, leave it outside for two hours. Keep adding an hour a day over the course of about a week.

After they are hardened off, transplant into the garden or into permanent containers. Dig holes six inches apart and make sure each hole is large enough to accommodate the roots.

Gently remove the seedlings from the tray, set them in the prepared holes, backfill with soil, and water in well.

If the resulting plant is one that you love, propagate it via tubers in the future so you can guarantee that it will be replicated faithfully.

Let’s Get This Party Started!

I have to confess that for me it isn’t all about saving money or developing new cultivars. I take a lot of pride in turning a little seed into a big, beautiful plant. It’s extremely fulfilling.

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What’s your goal with growing dahlia seeds? Are you hoping to breed a few new styles and shapes? Or just looking to save a few bucks? Let us know in the comments section below.

There’s so much more to learn about these colorful flowers. If you’d like to expand your knowledge about growing dahlias, you might find these useful:

  • Prevent Dahlias from Falling Over: Support Options for Your Plants
  • When and How to Water Dahlias
  • Why Dahlias May Fail to Bloom (And What to Do About It)
How to Propagate Dahlias from Seed | Gardener’s Path (2024)

FAQs

How to Propagate Dahlias from Seed | Gardener’s Path? ›

Moisten the soil and then gently sprinkle the seeds on top. Place a thin layer of the medium over them and gently press down on the surface of the soil with your hands. Set the containers on a heat mat set to maintain temperatures of 70 to 80°F and don't panic if you don't see any seedlings for a few weeks.

How to propagate dahlias from seed? ›

Specifically, sow seeds 5mm deep in seed-raising mix and keep them nice and moist. If you are sowing in spring or summer, you can do so directly into their final growing position in the garden if preferred. If you've played your cards right, your dahlia seedlings should appear in 10-14 days.

Will dahlias grown from seed produce tubers? ›

Yes! Dahlias grown from seed will produce tubers by the end of the summer. If you live in a climate where you can overwinter them in the ground, it's as simple as cutting the stocks down to the soil level. Mulching them will give them added protection through the winter.

How long does it take for dahlias to sprout from seed? ›

Germination will usually be fairly rapid, 10-14 days, quicker if the temperature is higher. When the leaves of the seedlings touch they can be potted up. Most of the seed will germinate together so the compost can be removed from the pot and broken up for the seedlings to be removed.

Can you scatter dahlia seeds? ›

Seeds should be started indoors at least 4 to 8 weeks before you want to plant them out. Dahlia seeds germinate sporadically, so be patient—they will come up but it can take up to two weeks. Direct-seeding into the garden isn't recommended.

Do dahlias grown from seed come back next year? ›

Will dahlia seeds turn into tubers? At the end of the growing seasons your dahlia seeds will have produced viable dahlia tubers that you can dig up and save for the following season. These dahlia tubers will produce identical plants to what was grown this year.

Do you pinch out dahlias grown from seed? ›

Pinching Dahlias

Like all pruning, pinching is a way of working with your plants, not against them, to produce the best possible plant. It can be difficult to do after taking so much care to grow your seedlings in the first place, but it's for the best.

Why are dahlias so hard to grow? ›

Dahlias send up shoots and unfurl new foliage quite quickly. All that growth requires a hefty amount of water. Dry soil stymies vigorous growth and bloom production. Aim to keep soil around dahlia tubers consistently moist after the first leaves emerge.

Can you collect seeds from dahlias? ›

These popular plants are traditionally grown from tubers, but did you know you can also grow dahlias from seeds and even harvest dahlia seeds from your existing plants to grow new ones? Harvesting dahlia seeds is simple, though there is no guarantee that the seeds you germinate will replicate the parent plant.

What month do you take dahlia cuttings? ›

We just make sure to keep trays evenly moist on heat mats and that works really well for us. Keep taking cuttings from the mother tubers until mid to late April. We usually take five to seven cuttings from each mother tuber.

Are dahlias easy to propagate? ›

It is actually far easier to propagate by division, especially for a beginner. Division Dahlias can be propagated at planting time by dividing the tubers. It is important to know the different parts of the tuber and know what they are for to be able to divide them.

Are dahlia cuttings better than tubers? ›

Tubers will produce a clone, or a plant exactly like the plant of the “mother” tuber. Propagation of dahlias by taking cuttings is the best method to increase stock of a favorite plant or to over-winter varieties that have tubers that are difficult to store.

Do dahlias like sun or shade? ›

Dahlias love to be in a sunny location— an area that receives at least 6-8 hours of direct sunlight is preferred. Dahlias will also grow in shady areas but generally will be taller and require more staking and care. Dahlias love to be in the dirt.

What month do dahlia seed germinate? ›

The main growing season is from March to June. Seeds need to be sown in early March or April. Start your seeds indoors for a higher rate of success. Germinate your seeds indoors in seedling cups in a mix of cocopeat and compost and place it in a well-ventilated area.

Do dahlias reseed themselves? ›

The dahlias we commonly cultivate in gardens today naturally reproduce themselves in two ways at once. They produce abundant flowers that (when pollinated and properly ripened) make beautiful seeds, and they also produce abundant tubers when grown well.

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