How to Grow Dahlias

Dahlias are tropical plants with gorgeous flowers, but you have to grow them during the warmer months. We live in zone 5b, so planting dahlias in our flower garden means some extra care.

Growing Dahlias is easy but they cannot tolerate frosts Dahlias need to grow and bloom during the frost-free window.

If you don’t know your growing zone you can easily Google it by typing your location and then find out your growing zone.

Although not commonly done, you can grow dahlias from seed
Although not commonly done, you can grow dahlias from seed

How to Grow Dahlias from Tubers

In general, it’s much easier to grow dahlia flowers from the tubers, not by growing seedlings. Dahlia bulbs are actually tubers, and you plant them in the spring and pull them up in the fall.

Dahlia tubers are planted in the spring after the risk of frost. You can plant them a week earlier with row covers.  If you don’t get frosts, then you don’t have to worry about this.

Be sure to draw a garden sketch of your dahlia types and where you planted them.

This is all a part of good spring garden planning. Keeping a garden journal will help once fall comes around and you need to dig them up and mark what varieties you have.

Cafe au Lait Dahlias

Where Should You Plant Dahlias from Tubers?

Dahlias prefer full sunshine. Loose soil works best for dahlias so the tubers have the space to expand. Your instructions should have spacing and depth requirements, but they grow roughly to the size of a rose bush.

The larger varieties need staking, especially dinner plate dahlias.

Stake a post on either side of the tuber when planting so you don’t damage the tubers later on. If you want to grow dahlias in containers, consider smaller flower sizes.

Enrich the soil with compost and add a light amount of organic fertilizer.

I used the perfect blend and azomite. You’ll want an organic fertilizer suited to blooming flowers, but as you need to save the tubers that’s also important.  Don’t overfeed.

Fall Dahlia Tuber Care

Dahlias are hardy to zone 8, sometimes zone 7 can offer protection for the winter. Other growing zones will need to dig out the tubers and overwinter them indoors. I waited until a light frost killed the above plant then harvested the tubers.

Pulling up dahlia tubers for overwintering

Pulling Up Dahlia Tubers

  • Pinch off the stem and the above ground plant matter
  • Gently remove soil around dahlia base
  • You should see tubers under the soil, gently lift them out
  • Separate your tubers from the central one.
  • Label them so you know what varieties you have for next spring
  • Brush off any dirt. Be gently handling them so they don’t become damaged
  • Allow the tubers to completely dry in the sun
  • Label the variety and store in peat moss or wood shavings in a cool place (garages or cooler basements work well)

Growing Dahlias from Seed

I did grow them from seed too to experiment, and those seedlings did bloom. However, it’s so much more work, and honestly, it’s not worth it. Sometimes buying seeds means more variety, but this isn’t the case with dahlias.

If you still want to grow dahlias from seed, you first have to start your seeds indoors about six to eight weeks before your last frost date. Dahlias need a lot of time to grow so they can produce flowers during the summer.

You can use paper towels to germinate dahlias from seed. Place your dahlia seeds on one wet paper towel and then cover them with another wet paper towel.

Afterwards, place the seeds and paper towels inside a zip lock bag and put it flat on a stable surface for three to five days. After that time, start checking the seeds for signs of germination. When the dahlia seeds have germinated, put the seedlings in a tray and use grow lights to help the dahlia seeds grow.

When the dahlia seedlings sprout leaves you will need to transplant them into larger containers so the roots can continue to grow. After there isn’t any chance of frost left, you can plant your dahlias outdoors.

You can grow Dahlias in containers

Do you grow dahlias? What is your favorite variety?

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