Everything You Need to Know About Dahlia Flowering Season

There’s no doubt that dahlias are some of the stars of summer. With flowers that come in just about every shape and color imaginable, these blooms know how to brighten up a space. Not only are they gorgeous, but they’re also long-lasting and offer rich symbolic value and lots of added benefits! With the proper care, dahlias can flower for up to four months. Keep reading to learn more about when and how long dahlias bloom.

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The Dahlia Season Essentials:

Dahlias are warm-weather flowers that bloom mid-summer through fall. They begin to bloom a couple of months after the soil warms, and continue to bloom until early to mid-fall. Both the environment and variety can impact when and how long a dahlia will bloom.


Dahlia Basics

Dahlia Basics

Dahlias are members of the Asteraceae family, along with daisies, sunflowers, and zinnias. However, unlike many of their family members, dahlias produce starchy tubers.

Rather than planting seeds, gardeners typically plant dahlia tubers. These tubers can produce flowers each year, as long as they do not succumb to cold temperatures.

Although all types of dahlias grow in a similar manner, you can find diversity in plant height, flower size, flower shape, and color (including the infamous black dahlia). There are 42 known dahlia species, but there are thousands of cultivars within these species!

Professionals break dahlias down into 12 different divisions:

  1. Anemone
  2. Ball
  3. Cactus
  4. Collarette
  5. Decorative
  6. Mignon
  7. Peony Flowering
  8. Pompon
  9. Semi-Cactus
  10. Single Flower
  11. Topmix
  12. Waterlily

While all of these divisions have variations in how their flowers look, they can all be treated similarly. Additionally, they will all bloom for a similar length of time.

Where are Dahlias Native To?

All 42 species of dahlias are native to mountainous regions in Mexico and Central America. Since these regions do not experience frost, dahlias grow as perennials.

When Are Dahlias in Season?

When Are Dahlias in Season?

In most areas, dahlias are summer and early fall flowers. Since they cannot survive cold temperatures, growers must wait until the ground warms to about 60ºF in the spring before planting dahlia tubers.

Once gardeners plant the tubers, the flowers will begin to bloom in about ten to sixteen weeks. In many places, this means the dahlia season starts in July.

Most dahlias will continue to bloom until fall frost arrives. This means dahlias will continue to bloom until mid to late fall in many areas.

Even if you live in an area without frosts, dahlia blooms will still slow in the winter due to decreasing light.

How Long Does the Dahlia Season Last?

How Long Does the Dahlia Season Last?

Dahlias will continue to bloom until they are killed by the first frost. Therefore, the length of the dahlia season depends on your climate. However, dahlia season lasts four to five months in many areas.

If you want to make dahlia season last a bit longer, you can try a few different techniques. Some of these will encourage dahlias to bloom earlier in the year, and others will extend fall blooms.

To get the dahlia season off to a quick start, you can plant tubers in a warm indoor area. This will give the plants a headstart while it is still cold outside By giving the tubers a chance to sprout and grow a bit indoors, they will bloom earlier in the year.

If you want to extend your dahlia season in the fall, you can utilize protective coverings. Frost cloth, low tunnels, and high tunnels can all be used to extend the season a bit longer.

However, since dahlias can grow four to five feet tall, covering them can take a bit of work.

Factors Influencing the Dahlia Season

Factors Influencing the Dahlia Season

Numerous factors impact the timing and length of dahlia season. These include the climate, dahlia variety, and when you plant dahlia tubers.

Climate

While dahlias are technically perennials, they are sensitive to cold. Therefore, gardeners in growing zones eight and below typically replant dahlias tubers each spring.

Since dahlia tubers aren’t cold-hardy, gardeners must wait until both the air and soil have warmed before they plant the tubers. If they plant the tubers too soon, they may become damaged or die.

A good rule of thumb is to wait until the last predicted frost date has passed before you plant your dahlia tubers outdoors. Additionally, you should wait until the soil has warmed to 60ºF.

Since the soil will warm later in the year in cooler areas, this means dahlias bloom later in the year in cooler regions. However, pre-sprouting dahlias indoors can help cooler regions catch up with warmer regions.

Additionally, a late frost can cause dahlia setbacks. Therefore, a warm spring will allow dahlias to bloom earlier than a cool spring.

Finally, cooler areas typically receive earlier frosts than warmer areas. Therefore, you can expect dahlias to bloom later into the season in warm areas.

Environment

If you’re not providing your dahlias with the proper sun, water, and soil, the plants will have a difficult time growing. And slow-growing plants mean blooms don’t appear until later in the season.

If you want your dahlia season to last as long as possible, follow these care guidelines.

Sun: Dahlias love sunlight, ensure they receive at least six hours of direct sun each day.

Soil: Choose loose and well-drained dahlia soil. Amend with compost if necessary.

Water: Aim to keep dahlia soil moist but not saturated through regular waterings

Fertilizer: Fertilize dahlias monthly with a slow-release fertilizer that’s high in potassium and phosphorus but low in nitrogen.

Additionally, you should make sure your plants have enough room to grow. Only plant dwarf varieties in dahlias, and provide adequate spacing between plants.

If you’ve planted your dahlias at the correct time but are not seeing any bloom after a few months, there’s a good chance improper care is to blame.

Pruning

While dahlias don’t need to be pruned, some growers opt to pinch or top their plants. This involves removing the terminal bud so the plant grows bushier.

If you pinch your plant, it will take a couple of weeks longer for it to flower. However, the plant will likely produce more flowers over the course of the season.

Dahlia Variety

While all varieties of dahlias are sensitive to cold, some will sprout and bloom quicker than others. In general, smaller flowers with fewer petals will bloom earlier than larger flowers.

With that said, you may notice a different variety blooms first each year.

Types of Early-Season Dahlias

Types of Early-Season Dahlias

If you’re looking for dahlias that bloom early in the year, you’ll generally want to look for small flowers. However, this is general guidance and not a rule. 

  • Kelvin Floodlight: a yellow decorative dahlia
  • China Doll: a yellow and pink waterlily type
  • Linda’s Baby: a peachy ball dahlia
  • Diva: a dark purple ball dahlia
  • Cornel: a ball shape and bright red color

Types of Mid-Season Dahlias

Types of Mid-Season Dahlias

As we mentioned above, it’s hard to say what variety of dahlia will bloom when. Factors such as temperature, water, and sunlight can all affect when a dahlia blooms.

With that said, these types of dahlias often bloom mid-season.

  • Café au Lait: a light pink décorative dahlia
  • Labyrinth: shades of pink and large blooms
  • Rebecca’s World: purple and white flowers

Types of Late-Season Dahlias

Types of Late-Season Dahlias

These varieties may bloom early in the year, but they are often some of the last dahlias to flower.

  • Spartacus: a decorative type with dark red petals
  • Breakout: pink and yellow hues and flowers up to 10” in diameter
  • Emory Paul: possibly the biggest dahlia, with flowers over a foot in diameter

Wrapping Up

Although the dahlia season depends on the climate, care, and type of dahlia, you can expect to enjoy these flowers for multiple months. So choose a few varieties and get planting! For more, see our in-depth guide to growing dahlia flowers in your garden and cutting dahlia flowers for a vase or bouquet arrangement.


Contributing Editor | Full Bio | + posts

Briana holds a B.S. in Plant Sciences from Penn State University. She manages a small market garden where she grows vegetables and herbs. She also enjoys growing flowers and houseplants at home.

Author

Briana holds a B.S. in Plant Sciences from Penn State University. She manages a small market garden where she grows vegetables and herbs. She also enjoys growing flowers and houseplants at home.

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