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Get a First Crack on Your Garden: Starting Dahlias Indoors

Last year, I mistakenly ruined my Dahlias’ garden allowing frostbite. And the bigger pain hit my belly when I tried to plant Dahlias in the summer. 

Soon I got my nerve with some research and successfully saved the remaining Dahlia tubers for growing.

Generally, there are multiple ways to start your Dahlias indoors, including tubers, seeds, and stem cuttings. All propagation methods need to wait for the late frost. After new sprouts, transplant them into a pot or garden and follow the usual care routine.
bloom of Dahlia
Growing the Dahlias from the seeds can be time consuming but is cost efficient as compared to that by tubers.

When growing Dahlia, temperature rules the plants considerably; if ignored, all hardships go in vain. 

Therefore, do not skim this article so you can have vibrant Dahlia blooms flourishing in your garden before the actual season arrives.

When Should I Start My Dahlias Indoors?

Dahlia (DAHL-ee-a) is a temperennial plant that produces colorful blooms in fall and summer.

Depending on your USDA zone, Dahlia can behave as both a perennial or annual plant.

If you live in USDA zone 8 or above, your Dahlia will tolerate the cold and make a dazzling comeback next year.

But if you live in USDA zones less than 8, you must take the Dahlia tubers indoors to protect them from rotting.

Dahlias are not frosty, hardy plants, so they need to overwinter to grow outdoors or in the garden.

Instead, starting these flowering plants indoors can preserve successful germination, thereby growing into bushy Dahlias. 

Starting Dahlias indoors from tubers
Before you use the Dahlia tubers, wake them up by keeping them at 60 to 70°F.

There are multiple choices for planting Dahlias, which need different periods and methods. 

In early April, you can plant the collected Dahlia tubers indoors to give Dahlias a headstart for earlier blooms.

Meanwhile, you need to sow Dahlia seeds indoors almost 2 to 4 months before the estimated date of last spring frost.

If you wish to grow the Dahlia plant from cuttings, take the stem cutting that has developed a few pairs of leaves for stem cuttings in late winter.

How Do You Start Dahlia Indoors?

Giving your Dahlia earlier push indoors means having colorful, magnificent Dahlia flowers almost a month earlier.

Furthermore, blooms will start in late July if you directly start Dahlia outdoors after the soil warms up.

starting dahlias indoors seedlings
You can start your Dahlias indoors via tubers, seeds, or via stem cutting.

You can plant Dahlias indoors and transfer them outdoors when they are old enough.

Before you make your hands dirty, gather these materials and tools!

Gardening GlovesTo protect your hand from getting dirty and getting hurt by the sharp tools
Gardening Scissors To trim away any decaying or dead roots in the tuber and for taking cutting
Multipurpose Compost MixNutrient rich potting mix to start off the Dahlia
Plant PotsSix to Eight inches plant pot with multiple drainage holes
Plastic TraysTo place the tubers, cuttings till they begin sprout out new growths

Now let us start the journey of beginning Dahlias indoors, shall we?

Method 1: Start Dahlia from Tubers

Starting Dahlias indoors from tubers is one of the most preferred methods over seeds or stem cuttings.

It is because starting Dahlias with tubers guarantees that the plant will carry the same parental characteristics.

But before you start, ensure you take out the tubers and let them become accustomed to 60°F to 70°F.

Keeping tubers in warm temperatures before planting is known as waking up Dahlia tubers.
  • Take out the potting mix and thoroughly moisten it but do not make it too wet or soggy.
  • Lay out the plastic tray with the moistened soil mix.
  • Remove any dead, damaged roots on the tuber with the help of sharp, sterilized scissors.
  • Place the tubers horizontally on the tray and label them with details of the tubers to remember.
  • Maintain the temperature at around 60 to 70°F to encourage efficient growths on tubers.
  • Once you notice new growths on tubers, consider transplanting them into individual pots.
  • Use a 6-8 inches pot with multiple drainage holes and partially fill it with potting mix.
  • Plant the individual tubers in the pot with the shoots and eyes of the tuber facing upwards.
  • Add potting mix to cover the tubers and water thoroughly.
  • Ensure to place the pot in a sunny location with full access to sunlight. 
Grow light
If the light is scarce, you can keep them under grow light to improve their performance.
  • Use artificial grow lights of the full spectrum to compensate lack of sunlight.
  • You should not water your tubers in the first few weeks to avoid rotting.
  • Wait till the outdoor garden soil becomes warm enough.

Dahlia tubers can take 2-8 weeks to develop sprouts depending on the varieties. 

You shall consider transplanting your new Dahlia plants outdoors after the last frost to let them thrive to their maximum potential.

Method 2: Start Dahlia from Seeds

Although growing Dahlias from seeds is a bit delicate, it is still the best option if you want a new Dahlia variety.

In the context of cost, starting Dahlias from seeds is much cheaper and more affordable than tubers.

Meanwhile, Dahlias grown from seeds take almost four months to make beautiful, new blooms.

Therefore, for perfect timing, you must plant your Dahlia seeds indoors 42-56 days before the last frost.

starting dahlias indoors from seeds
Growing Dahlia from seeds is cheaper compared to growing it from tubers.

Now follow these steps carefully to start Dahlias indoors efficiently from seeds.

  • Prepare or buy an ideal soil mix to initiate the germination of Dahlia seeds.
  • You can directly sow the Dahlia seeds in the soil or follow the paper towel method to germinate them.
  • Get a germination tray and fill the tray with potting mix suitable for seeds.
  • Sow the Dahlia seeds at 1.5cm depth and one inch apart.
  • Subtly cover the seeds with the potting mix and gently moisten the soil with the help of a mister.
  • Place the germination tray in a brightly lit area and maintain a temperature above 70°F. Or use artificial grow light and a heating mat under the tray.
  • Ensure the soil is slightly damp and moist throughout the process, and do not add fertilizer to the mix.

You will be able to see seeds germinating with new sprouts in 1-2 weeks. 

Once the new seedlings have developed a few pairs of leaves or have 3 inches of height, consider transplanting them into individual pots.

Meanwhile, you can wait until the outdoors is warm and welcoming for Dahlia seedlings to survive.

starting dahlias indoors seedlings
Dahlia grown from seeds usually takes 100 to 120 days to produce full fledged colorful blossoms.

You may wonder if Dahlias grown from seeds will have tubers. The answer is yes!

Dahlias grown from seeds have tubers formed at the end, but they are not worth harvesting. 

Method 3: Start Dahlia from Stem Cuttings

Another excellent method of starting Dahlias indoors is via stem cuttings.

Though the tuber is the beginning source for propagation, the cuttings can also help. 

Generally, starting Dahlias indoors from stem cuttings can help you have multiple Dahlia plants from a single healthy tuber.

Depending on the number of sprouts from tubers, you can snip off over 3-inch long stems.

Within a month, if the tuber is healthy, it will add another shoot ready for you to snip off and continue stem cutting.

Follow these steps for starting Dahlias indoors from stem cuttings without further ado.

  • Select healthy stems with more than three pairs of leaves or a height of at least 3 inches.
  • Use sterilized sharp pruners to take clean stem cuttings to avoid dangerous infections.
  • Ensure to slice a tiny portion of the tuber just above the lowest node along with the stem cuttings.
  • You can discard other lower part leaves by leaving the top two or three leaves on the cutting.
  • Apply rooting hormone on the freshly cut ends of the stem cuttings to encourage better and faster growth.
  • Use a 3-4 inch pot, fill two-thirds with potting mix, and plant the cutting into it.
  • Ensure to place Dahlia plants in a warm place with enough bright sunlight (at least 12 to 14 hours).
  • Keep the cutting 4 or 5 feet under the incandescent grow light to provide enough light.
  • Place the plants’ pot over the heating pad to maintain the temperature at 65-75°F.
  • You can also cover the pot with breathable clear plastic to trap the humidity, but too much moisture can cause rot. So, be careful!

Generally, you can notice the observable growths on the cuttings within two or three weeks.

Get some help from this video!

Tips for Starting Dahlias Indoors

If you do not want to risk your hardship journey of starting Dahlias indoors, never avoid the following tips.

  • Provide your new Dahlias with sufficient sunlight, and opt for an artificial grow light if needed.
  • Until and unless the Dahlias have solid roots developed, avoid deep watering.
  • Avoid watering the Dahlia tubers in their first weeks to prevent overwatering, causing tuber rotting.
Potted Dahlias need additional care to grow.
  • Give your plant balanced all-purpose slow-release fertilizers with lower nitrogen content.
  • Generally, fertilizers of NPK ratios 5-10-10 or 10-20-20 suit best to encourage splendid blooms.
  • Maintain the soil slightly acidic at a pH level of 6.5 to 7.0.
  • When planting Dahlias tubers, ensure to keep the eyes of the tubers facing upwards with the crown buried under the soil.
  • Once you are ready to transplant the Dahlias outdoors, find a place where the sun shines for at least 6-8 hours daily.

Though you can grow Dahlias indoors in containers, the best and ultimate environment for them is the garden or outside. 

With proper care and attention, you can enjoy the colorful blooms of Dahlia earlier than others.

Editor’s Note

Starting Dahlias indoors is a foolproof method to save the fatal outdoor condition and enjoy the aesthetic beauty of Dahlias for a longer time.

Dahlia provides three different methods for starting indoors. So, you can leverage any one process that you feel is feasible.

Also, follow the steps carefully with proper care to get blessed with profuse blooms of Dahlia. All The Best!!!

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