Plant Care

Why are Chrysanthemum Leaves Turning Black? (Quick Answer)

In this article we want to answer this question: Why are Chrysanthemum Leaves Turning Black? What could be the reasons for this phenomenon?

Chrysanthemums are quite resistant flowers that grow in almost every area. But in some cases chrysanthemum (mums) leaves start to turn black and it is difficult to understand why.

To save the chrysanthemum, it is important to correctly determine the causes of blackening of the leaves:

Why are Chrysanthemum Leaves Turning Black:
1. Septoria (Leaf spot)
2. Ascochyta Chrysanthemi
3. Gray rot (Botrytis)
4. Waterlogging
5. Air Temperature Imbalance

One of the main causes of blackening of the leaves of chrysanthemums are fungal diseases. It is important to understand that all such infections accumulate in the soil, in the roots, on fallen leaves, in the case of long-term cultivation of a crop in one place.

The harmfulness of the disease also increases in thickened plantings, with sharp air temperature fluctuation, over drying or waterlogging.

1. Chrysanthemum Septoria (Leaf spot)

Chrysanthemum leaves begin to turn black when affected by Septoria or Leaf Spot ( Septoria obesa or S. chrysanthemella). This fungi disease will remain in plant residues for years and spread through water splashes, especially in humid environments.

First, yellowish-brown rounded spots appear on the leaves, which later darken and become almost black. Gradually, the affected areas increase and merge to cover up the entire leaf. When the spots cover most of the chrysanthemum leaf blade, it dries up.

The dark-colored spots extend from the base of the mums upwards, causing the chrysanthemums to wither and die.

If you do not start treating septoria, then it can lead to the complete death of the plant.


Infected leaves should be cut off and burned immediately. If the disease is too strong, you will have to destroy the entire chrysanthemum before it infects its neighbors plants.

To prevent this from happening in the first place, you can spray a tea infusion made from onion skins or horsetail as a preventive measure. Many chrysanthemum species are largely resistant to fungi, but unfortunately there is no such thing as 100% protection.

For its control it is recommended to avoid wetting the foliage and carry out preventive treatments:

  1. The darkened leaves from mums are removed and burned.
  2. Infected chrysanthemums are sprayed with fungicides.
  3. To protect flower beds, black wilted leaves and vegetation should be removed.

Speaking of wilted leaves on chrysanthemum, I have identified 4 causes why are Chrysanthemums wilting and how to treat each cause.

2. Ascochyta chrysanthemi (Mycosphaerella ligulicola)

Ascochyta chrysanthemi or commonly know “flower blight of chrysanthemum” is another type of fungal disease that affects not only the leaves, but also other parts of the chrysanthemum.

First, black or gray-brown spots form on the mums leaves, which spread to the entire surface of the leaf blade. The leaves dry up and hang along the stem. Mottling may appear on the flowers, and the middle rots.

This fungus is spread by wind and splashing water and favors humid weather conditions. Decomposition of flower buds may occur before they open, and infection may spread to the peduncle. 

Symptoms such as the decomposition of flower buds appear before they open and whose infection extends to the peduncle.


As with septoria, infected leaves must be destroyed immediately to prevent the spread of the disease. Water splashes must be avoided, the substrate and pruning tools must be disinfected, etc.

For its control we will do foliar treatments with specific fungicides.

3. Gray rot (Botrytis)

If the chrysanthemums have turned black, the cause may also be gray rot (Botrytis). Chrysanthemum sp. (Sleeping Chrysanthemum) can be affected by Botrytis on buds, flowers, leaves, and stems. 

Infected mums leaves are light to dark brown (appearance of a fuzzy gray appearance requires appropriate moisture conditions). Infections begin as small black dots and rapidly expand to reach the entire bud or flower. 

Both adults and young mums seedlings are susceptible to damage, especially from cuttings. 

First of all, the leaves dry up, then the rest of the chrysanthemums. Gray rot affects all garden flowers and vegetable crops and can lead to the death of the plant.


This disease is favored by cool temperatures and high relative humidity. It is controlled with foliar treatments with specific fungicides and keeping the crop well ventilated with pleasant temperatures.

Gray rot often appears during the cold season, as well as during the flowering period. All affected mums leaves must be removed and burned.

4. Waterlogging

If the chrysanthemum is watered too often, the leaves will turn black. This is due to the fact that the water in the pot stagnates, the roots begin to rot and the plant is sick. To avoid this, you need to take a pot with good drainage. If the plant has a lot of leaves turning black, then you need to transplant the plant into another pot.

If you notice that leaves are black, you must loosen the soil and stop watering. To know when to water again, check the soil moisture by pressing two fingers 4-5 centimeters deep in the substrate.

Watering the substrate is not worth it if the top layer does not dry out to a depth of 5 cm. In winter, it is worth reducing the frequency of moistening and transferring from a hot apartment to a cool balcony or loggia. This will allow the plant to rest, gain strength and give its owner new buds.

Also, ordinary water can become the cause of blackening of the ends of the mums foliage. Often this problem occurs when the owner starts using cold water for irrigation. It should be at room temperature.

If water for irrigation is drawn from the water supply, then it is advisable to store it in an open container for 2 days. This is required so that the amount of chlorine in the liquid decreases, as well as heavy salts settle.


Regarding irrigation, the chrysanthemum needs water frequently so that the soil is always moist, but be careful with waterlogging, since excess water can rot it. In order to avoid this, the soil must be well drained. Also, spray frequently with water, without wetting the flower buds.

After watering, it must be drained. Next time, wait until the top layer of the soil dries out, only after that it can be moistened.

If the plant is watered according to the instructions, but its leaves are still turning black around the edges, a spray bottle can help. Most houseplants are of the type that best absorbs and processes water from the surface of the leaf.

5. Air Temperature Imbalance

The last reason why mums leaves turn black is a sudden change in air temperature. Low indoor air humidity is the first and perhaps the most important reason for drying and blackening leaves. 

In most cases, nothing can be done about this, since after starting the heaters, the humidity indicator almost immediately drops to 30 %. And this is almost an extreme value for many flowers. Only cacti are able to experience this painlessly.

Too high air temperature (especially coupled with low humidity) can lead to blackening and drying of leaves. For this reason, it is very important to ensure that in winter the thermometer does not fall below 60°F (16 degrees Celsius) into the dwelling and does not exceed 64°F (20 °C)

The optimum temperature for most indoor plants like chrysanthemum will be 62°F (18 degrees Celsius). Those who use additional heating devices in the house need to be especially careful.

Cold air from the window contributes to the rapid withering and blackening of the leaves. Most often, a couple of minutes is enough to start the destructive process. For this reason, it is very important to either rearrange the plant pots or initially put them in places where there will definitely not be cold air.

Important. In winter, it is advisable to keep the plants in a cooler place at a temperature of 60-62°F (18-20°C), away from heat radiators.


It usually occurs after close contact with heating appliances. If you notice black leaves on a chrysanthemum flower, keep it away from hot appliances.

If the reason lies in dry air, then a simple water spray from a spray bottle will help. The procedure is recommended to be carried out in the morning and always with settled water at room temperature. 

In the evening, you should not resort to such activities. Water may not have time to be absorbed, and the coolness of the night will provoke hypothermia of the leaves and even their possible rotting.

How to prevent Chrysanthemum Leaves from Turning Black

The following steps should be taken to prevent black leaves on Chrysanthemum:

  1. Treat the chrysanthemums with fungicides 3-4 times per season (during shoot growth and the appearance of the first leaves).
  2. You should spray not only the leaves and shoots, but also the soil around them.
  3. Monitor soil moisture and water it only when necessary using warm water.
  4. Spray chrysanthemum with fertilizer based on potassium and phosphorus to increase resistance to diseases.
  5. In the autumn, clean the soil bed and remove all the dried leaves and debris.
  6. In order to prevent fungi, wilted and fallen parts of mums in flower beds should be destroyed in a timely manner.
  7. For any garden infection, diseased leaves are best burned: they are not recommended for use as compost, so as not to transfer fungal bacteria to healthy crops.
  8. When planting chrysanthemum, choose a place exposed to full sun. For both potted and open field cultivation, mulch to protect the soil from evaporation in midsummer and protect the roots from cold in midwinter.
  9. If the disease nevertheless attacked the chrysanthemum flower, it is necessary to immediately get rid of the darkened leaves and treat the soil bed with fungicides. 


As you can see in this article, there are several reasons why chrysanthemum leaves are turning black, but the faster the causes are identified, the faster these causes can be eliminated.

Timely detection of signs of damage will help, if not to save the mums, then to maintain the health of other garden flowers. 

Are chrysanthemum leaves prone to disease?

Depending on the location and care, chrysanthemums are susceptible to disease.
Leaf spot disease is common in chrysanthemums . As the name suggests, you can recognize these by the fact that yellowish-brown spots appear on the leaves, which later turn black. With the help of regular fertilizer (alternatively long-term fertilizer) you can strengthen and protect your chrysanthemum .

Why are Chrysanthemum Leaves Turning Black?

The main reasons that cause black leaves on Chrysanthemum are: fungal disease, excessive watering, too dry air in the room and heat. If you see that the leaves have turned black, and the soil is too wet, you should limit watering for a while.

Andreea Tapu

Andreea TAPU is a passionate gardener with over 5 years of experience in cultivating a wide variety of plants and flowers in her garden. As the author and creator of, she is dedicated to sharing her knowledge and expertise with others, providing practical tips and advice to help gardeners of all levels achieve success and enjoyment in their gardening pursuits.