Dahlia Leaves Turning Yellow


Homeowners love to grow dahlias for colorful, gorgeous flowers that bloom from mid-summer through autumn. But until the leaves turn yellow.

Chances are your dahlia leaves turning yellow as you are reading this. However, do not worry anymore as this article contains everything you need to know regarding this topic. We compiled the reasons for happening this with some effective solutions.

So, let’s get started, shall we?

What Causes Dahlia Leaves Turning Yellow?

Before you go for the solutions, let’s make sure which difficulty your plant is facing. Several causes lead dahlia leaves turning yellow. Here is a shortlist of the reasons:

  • Clay heavy soil
  • Improper soil pH
  • Nutrient deficiency
  • Diseases

Few of these reasons are similar for most plant leaves turning yellow.

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Photo of Dahlia flower
Photo by Rqs

How To Get Rid of Yellow Dahlia Leaves?

Now, let’s move into the symptoms and solutions.

Clay Heavy Soil

If you live in an area that is plagued by clay soil, your plants face a lot of problems. Dahlia leaves can turn yellow if there is clay-heavy soil. But how may you tell whether your garden has clay-heavy soil or not?

Well, to test it, take a handful of damp soil as well as squish it in your hands for a few moments. Now, open your hand and check if the soil ball you just formed crumbled. If it does not then you likely have clay-heavy soil. Another indication you may want to see- a slimy or greasy feel when the soil is wet. Also, the soil seems dusty or hard if the soil is dry or if you have any drainage issue.

So, all of the above-mentioned things indicate that your soil contains too much clay.

Solution: You can add compost to your clay soil for an improvement. To do so- choose a flower bed that you want to improve the soil and then place the compost on the flower bed. Now, dig it using a shovel or a tiller.

Otherwise, you can simply lay the compost on the top of the soil. Then let it sit for one or two seasons. It would be best if you apply the compost on the clay soil early in the fall, then let it sit till spring. The compost will be working its way into the top few inches of the clay as well as give your flower bed a good start.

The second option to improve your soil quality is gypsum because it will help to push the clay soil particles apart and also make room for proper water retention and drainage.

Improper Soil pH

Another major cause that leads dahlia leaves turning yellow is improper soil pH conditions. The expected pH is the middle range of the pH scale because this range is the best for bacterial growth in the soil to enhance decomposition.

Why is decomposition so important? Well, because this process releases minerals and nutrients into the soil and makes them available for the plants or shrubs to use. So, ultimately, fertility depends on pH. Moreover, the middle range of pH is perfect for micro-organism that converts nitrogen in the air into such a form which the plants can readily use.

Solution: If you continuously apply inorganic fertilizers to the soil, this will make your soil even more acidic over time. So, use a rotation of organic and inorganic fertilizers that will help in keeping the pH of your soil balanced.

Or, you can add amendments to the soil after testing your soil’s pH. It will also alter the soil’s pH rating.

Nutrient Deficiency

Mainly, lack of magnesium causes yellowing your dahlia leaves. Magnesium is a crucial nutrient for plants because it works as a powerhouse behind the photosynthesis.

Chlorophyll can’t capture sun energy without magnesium that is needed for photosynthesis. And yes, it is magnesium that plays a significant role to give leaves their green color.

If the soil is not rich in organic matter or is very light then there is maybe magnesium deficiency. Otherwise, heavy reasons are responsible for magnesium deficiency in the soil. Moreover, if your soil contains a high amount of potassium then plants can absorb potassium instead of magnesium.

Solution: Apply rich, organic compost annually to provide magnesium to your plants. Compost will conserve moisture as well as help to keep nutrients from leaching out during heavy rainfall.


Another common cause for yellow dahlia foliage is fungal and rot disease. Because rotten tubers fail to support the growth of healthy foliage and blooms. Leaves start fading and over time, you will see your plant leaves turning yellow.

A fungal disease named smut can cause yellow mottling in the dahlia leaves.

Another problem is chlorosis. When your plant can’t produce enough chlorophyll and over time, the leaves will fade to a pale yellow- this situation is called chlorosis.

Solution: For the disease smut, remove plus destroy the affected plants as well as all of the symptomatic leaves. Use a hand pruner to remove them. Then treat with a fungicide.

For root rot, cut away infected areas. Then, treat the cut sections with a 50:50 mixture of sulfur and hydrated lime.


Question: Should I remove yellow leaves?

Answer: If the leaves look unappealing or bother to you, you can snip them off. But it’s not necessary.

Question: How often should I water dahlias?

Answer: Provide a deep watering 2-3 times a week from a minimum of 30 minutes with a sprinkler. And, keep in mind that overwatering can cause root rot.


So, this is all we stored for you. At the end of the article, hopefully, you now know why your dahlia leaves turning yellow and how you can possibly solve it.

Dahlias require proper maintenance, so, if you take proper care from the very beginning, you will get the best outcome. Try to find out if any difficulty your plant is facing and treat them on time.

Good luck!

As an Amazon Associate I earn from qualifying purchases.

Celina Nance

It’s been a life-long wish of Celina Nance to have a lawn full of colorful flower beds. But living in Arizona city, that seems kind of impossible. But Celina Nance didn’t stop and created a full-form balcony garden instead. And he often shares stuff that he does/solves/innovates throughout the journey.

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