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Cutting Dahlias for Continuous Blooms: How To Do It Correctly

Dahlias are showy flowers with exquisite beauty, but there’s a mystery surrounding their blooming habits and vase life.

Dahlias only last 3 to 4 days in the vase before they wilt, so some people might cut the buds from the plants before they open in order to add a few extra days to the flower’s vase life. However, that often backfires.

Will dahlias bloom after cutting? Contrary to common belief, dahlias do not open after cutting. Unless the flower is at least three-quarters open and the green color in the center has disappeared, the flower is not ready for cutting just yet. If the back petals are already wilting on the dahlia, it’s already past harvest time.

Having a short vase life doesn’t deter many people from growing dahlias and enjoying their bright colors. The more you cut the flowers, the more new buds will emerge on the dahlia for continuous blooms.

Here’s how to do it the right way.

Dahlias’ Bloom Time and Cycle

Although dahlias are perennials, they tend to behave like annuals. In other words, if you keep cutting the open blooms, the plant will keep producing new flowers.

This continuous blooming makes up for the flower’s relatively short life after cutting. 

How Long Do Dahlias Bloom?

Dahlias will keep blooming for about 120 days. In other words, your dahlias have a bloom time that spans more than one season. If the dahlia blooms in the mid-summer, it will continue until the end of autumn.

Some dahlia varieties are late bloomers and will keep producing flowers well into the winter under the right conditions. 

Dahlia Growth Stages

Like many other flowering plants, dahlias go through the usual four stages of life. They start with seed germination, vegetative growth, flowering, and end with seed production.

Here’s the lowdown of each stage.

  • Germination: The seeds of dahlia take between 10 and 21 days to germinate. They need a soil temperature of around 70℉ (21℃) for successful germination.
  • Vegetative Growth: During this phase, the plant develops a robust root system and reaches its maximum height and width. The foliage grows higher and wider within the next 3 to 8 weeks. No flower buds yet.
  • Flowering: This is the longest stage of the dahlia’s life. It lasts anywhere from 10 to 12 weeks. During this stage, the plant stops producing leaves and focuses its energy on growing flower buds that bloom in the right temperatures. New buds will grow to replace any flowers that are cut or fade under cold temperatures.
  • Seeding: When the flowers open, the next step is pollination. A pollinated flower will fade as seeds develop inside of it. If you don’t cut the flowers before pollination, you can keep them to harvest the seeds for the next season.  

Dahlia Bloom Cycle

The dahlia bloom cycle is similar to other flowers. The buds emerge once the foliage is fully developed. The timing of the first flowers depends on the variety of dahlia you grow.

Some dahlias are early bloomers, and the flowers will open in mid-spring. Most dahlias start to flower in mid-summer, although some varieties, like Spartacus, are late bloomers and will continue to bloom in the winter.

Ideal Conditions for Growing Dahlias

To ensure the success of a dahlia, make sure it’s getting enough light and water and the temperature is neither too cold nor too hot. 

Soil

The ideal soil for dahlias is loamy, fast to drain, and rich. Loosen heavy soil with aged manure or compost to improve the texture and drainage. Make sure the soil pH is between 6.0 and 7.5. 

Light

Dahlias need between 6 and 8 hours of sunlight a day during the growing season. The morning sun suits the flower better since the afternoon sun makes the blooms wilt faster.

Choose a north- or east-facing spot that is protected from strong winds.

Water

Dahlias need watering 2 to 3 times a week during the peak of the summer if it hasn’t rained. For late-bloomers, water once or twice a week, and avoid getting the foliage wet.

Fertilizer

Dahlias need a mild fertilizer that is low in nitrogen. Apply the fertilizer once every 3 to 4 weeks after sprouting until the end of the bloom season.

How To Cut Dahlias for More Blooms

Several varieties of brightly colored dahlia flowers.

Dahlias behave like annuals whose ultimate goal is to grow as many flowers as they can to produce seeds. You can take advantage of this fact to increase the blooms of a dahlia.

Cut the open flowers once the green color in the center is gone to encourage more flower buds to emerge. The best time to cut the flowers is in the early morning.

You also need to deadhead the spent flowers because once the flowers produce seeds, the plant calls it a season and stops producing new flowers. 

Will Dahlias Open After Cutting?

No, dahlias will not open after cutting. If you cut a bud or an immature dahlia flower, it will remain as is until it withers and dies.

The best time to harvest a dahlia flower is when it’s three-quarters open and the center of the flower is no longer green.

What To Plant With Dahlias

Dahlias do well with other flowers. Here’s a list of the best plants to grow with dahlias.

  • Allium 
  • Blazing star
  • Black-eyed Susan
  • Anise hyssop
  • Aster
  • Bee balm 
  • Agapanthus

Related Questions:

How Long Do Cut Dahlias Last?

Cut dahlias have a vase life of between 3 and 4 days at most, but since the dahlia is a prolific plant, you’ll continue to get more fresh flowers during the long bloom season.

How Long Do Dahlias Last in the Garden?

Dahlias keep blooming for 120 days. When the blooming flowers are cut, new flowers emerge to replace them. That way you will enjoy fresh flowers throughout two seasons per year.

Can You Leave Dahlias in the Ground Over Winter?

You can only leave dahlias in the ground over winter in Zones 8 and above.

In colder Grow Zones, the dahlia will rot in the ground during the winter months, but they can be lifted and stored in a dry, cool place until spring arrives and replanted in the garden.

Conclusion

Dahlias have a long bloom season that lasts for about 120 days. To keep the dahlia producing new flowers, cut the open flowers and deadhead any spent ones.