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When Do Dahlias Bloom?

Most dahlia plants will begin blooming in mid-summer around July. Dahlia flowers generally continue blooming until winter when killing frosts arrive. However, dahlias can sometimes fail to bloom if conditions are not ideal. Even things that seem good (like too much organic fertilizer) can cause blooming issues. If your dahlias are blooming late, you want to make sure the plant is getting enough sun and water to bloom on time.

When do dahlias bloom?

What Month Do Dahlias Flower?

Traditionally, dahlia flowers arrive in July. The rule of thumb is that they arrive about 8 weeks after planting. Since the ideal planting time is May in many regions, this means you’ll typically see your first blossoms in July. Dahlia varieties are known for blooming all at once or relatively close together. Thus, it’s usually easy to spot a late bloomer quickly. 

  • July is the traditional flowering month for decorative dahlias.
  • Dahlias tend to bloom as a group, making it easy to find problem bloomers quickly.

Dahlia growers recommend keeping an eye on any late bloomers for about a week after the first bloom. If they continue to fail to bloom after that week, then you know something is wrong.

Why Are Your Dahlias Not Blooming?

Dahlias can fail to bloom or bloom late for several reasons. Below, we’ll go into the most common issues that can prevent dahlia blooms and how to fix them.

Overfertilized or Wrong Soil Type

Too much nitrogen from fertilizer encourages dahlias to grow green foliage but prevents flowering. This results in bushier plants with flower buds that struggle to blossom. Be sure to cut back on fertilizer if you notice your plant is growing more true leaves and not flowering.

  • Avoid fertilizers with excess nitrogen as that can stunt bloom development.
  • Make sure you plant your dahlias in sandy, slightly-acidic, well-draining soil.
  • This fertilizer is perfect for promoting dahlia flower production.

Additionally, dahlias need well-drained soil. Sandy soil is best because it keeps excess water from pooling on the soil. Mildly acidic soils will also produce the best growth conditions for your dahlias.

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Not Enough Pruning

Dahlias need occasional deadheading to spur additional bloom growth. Deadheading is when you prune dead flower heads off of your plant. If you leave dead flower heads on, the plant will not grow new flower heads. Use a sharp knife or pruning shears to clear away dead flower heads.

  • Remove flower heads after they have bloomed.
  • Pruning dead flowers (called “deadheading”) helps encourage regular flower production.

Many flowering plants switch to seed production once they have flowers. This means that less energy will be devoted to growing single flowers than to spreading seeds. Deadheading helps delay seed production and refocuses the plant on growing beautiful flowers again. It is one of the best pruning tactics to get more dahlia flowers.

Your Dahlias Lack Water

Lack of water can prevent your dahlia from producing beautiful blooms. Dahlias need 1 inch (2.5 cm) of water per week before blooming and 2 inches (5 cm) of water per week after blooming. This helps maintain adequate soil moisture for the dahlia root ball. 

  • Water dahlias with 1 inch (2.5 cm) of water every week until they flower.
  • Once your dahlias begin flowering, double your watering to 2 inches (5 cm) of water per-week.

Another option for watering your dahlias is to set up drip irrigation. This will regularly leak water into your dahlias and ensure consistent soil moisture. Be sure to water dahlias regularly no matter which method you go with.

Not Enough Sunlight

Dahlias thrive in full sun, meaning 6–8 hours of sunlight each day. Direct sunlight is best for dahlias. If your dahlias are not flowering, it could be because they’re not getting enough sunlight. Dahlias in containers, for instance, may need up to 10 hours of indirect sunlight to make up for the lack of direct light. For more information, check out our guide to sunlight needs for dahlias.

  • Dahlias achieve their best active growth in full sun conditions.
  • Be sure to give your dahlias additional hours of sun if they’re growing in indirect light.

Make sure your flower bed or dahlias in containers are placed in a sunny spot. This will help to encourage the beautiful growth of flower heads. If they don’t receive adequate sunlight, your dahlias won’t produce any flowers.

Do Dahlias Flower All Year?

Dahlias typically flower from July until the plant dies in winter. Killing frosts are the big enemy of dahlia blooms. One frost will kill your dahlias. Dahlias are not particularly winter hardy so you may want to take precautions to protect them from the danger of frost if you wish to encourage late-year blooms.

  • Dahlias begin blooming in July and stop blooming when winter arrives.
  • Once the chance of frost increases, your dahlias will stop blooming.
  • You can help your dahlias bloom later into the year by keeping your flowers warm.

You can prolong dahlia flower lifespans by protecting your flowers from the cold. Growing dahlias indoors, using a heating pad to maintain soil temperature, and other tricks can help. However, even these can’t put off the inevitable. Dahlias are annuals that will not survive the winter.

How Late Will Dahlias Bloom?

Dahlias will bloom up until cold temperatures arrive, typically in October or November. Dahlias begin blooming in July. If your dahlias have not yet begun blooming in July, there is likely an issue preventing blooming. 

  • Dahlias can continue to bloom as late as November.
  • Dahlias rarely begin blooming later than July.
  • If you have a dahlia that hasn’t bloomed by late summer, something is likely wrong.

Dahlia tubers that haven’t bloomed in July likely have something wrong. If this is the case, it is time at this point to start figuring out what could be causing the issue.

How Long Do Dahlias Bloom?

Dahlias tend to bloom for about 4 months. Dahlias stop blooming when frost sets in, so bloom length vary by climate. In cold climates, you may only get 3 months of bloom. In hot climates, you can sometimes get as many as 5 months of flower production from your dahlias.

  • Dahlias bloom for an average of 4 months depending on your regional climate.
  • Cold climates will only produce blooms for 3 months, hot climates for up to 5.

A dahlia enthusiast will recommend growing dahlias indoors or in a greenhouse. This will help maximize the lifespan of your dahlia flowers. This way, you can enjoy up to 5 months of incredible blossoms.

What Time of Year Do Dahlias Bloom?

Dahlias begin blooming in July. Once they start blooming, dahlias flower for 3–5 months. If your dahlias do not bloom by August, you should evaluate your flowers for potential issues. Here are the important lessons we covered when it comes to dahlia blooms:

  • Most varieties of dahlias bloom in July.
  • Dahlias don’t flower all year but will stay in bloom until winter frosts kills the plant.
  • Dahlias rarely begin blooming later than July.
  • If your dahlias aren’t blooming by August, check for common issues like overfertilization, insufficient sunlight or water, or not enough pruning.

By providing low-nitrogen fertilizer, increasing watering once flowering begins, and deadheading old blossoms, you’ll get more from your dahlia plant. These factors—combined with adequate sunlight—contribute to a riot of gorgeous blossoms.

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