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Why Are My Mums Dying? (5 Common Reasons)

Why Are My Mums Dying? (5 Common Reasons)

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Chrysanthemums, or more affectionately known as ‘Mums’, are gorgeous and colorful plants whether placed indoors or outdoors. Did you know that they’re an annual species, too? Because of that they require specific care instructions.

From my experience, Mums aren’t necessarily high-maintenance – they’re simply susceptible to a lot of things, including mildew, fungus, aphids, and more. This makes the plants hard to keep alive over the winter, too, especially if they’re outdoors.

But not to worry! My goal today is to tell you about the common culprits behind your beautiful Mums dying and how you can help revive it. Ready? 

5 Common Reasons for Mums Dying (with Solutions & Tips!)

Pay attention to what I’m about to tell you. This section diagnoses what’s wrong with your Mum while also providing solutions, tips, and easy fixes along the way. So, stick around.

1– An Immature Root System

All types of potted Chrysanthemums become root bound fast. Hardy Mums only survive winter when they have a strong root system. They can only get that when they are planted in early spring to benefit from the full sun in the summer.

As such, buying a potted Mum near fall season is likely to die when the first frost hits. The roots will not be strong enough to support it over the winter.

Additionally, how you care for Chrysanthemums depends on when you buy them and how you intend to grow them. In the spring, for instance, perennial varieties of Mums should be planted outdoors.

When working with potted Mums, on the other hand, know that you are caring for a hardy variety that can cope outdoors. If what you have is an annual variety though, often purchased after the spring, those are usually difficult to keep alive beyond a single season.

Why? Because those annual Mums are forced to bloom. They look great in garden centers and nurseries, enticing customers to buy them. But the root system will rarely be strong enough to survive more than one season.

So, in the first year, the challenge with annuals is just keeping them alive by nourishing the rooting system while providing adequate growing conditions that doesn’t force the plant to bloom too early. 

When they are immature, the best thing you can do is focus on caring for the root system. Worry about blooming once it has the nutrients and strength to re-bloom.

2– Lack of Mulch


Hardy Mums can last for years in the garden provided they are in an area that receives plenty of sunlight and that you don’t ignore them during the growing season.

No Mums are cold-hardy, though. So, while perennials are hardy to an extent, there’ll always be parts of the plant that die off in the winter.

The extent of that damage over the winter will depend on the level of protection in place – and the best protection is a deep layer of mulch. The alternative is to accept that the plant won’t survive the frost and cut it back to near ground level before the frost hits.

3– Adverse Weather & Overwatering

Very few plants fare well with too much water. For garden varieties of Chrysanthemums, heavy rainfall will result in Mums turning brown. In most cases, when that happens, the mushy parts of the plant will need to be removed.

Given that these are late bloomers, if you are in a region that frequently gets heavy downpours, invest in plastic tarps to shelter any fragile plants in your garden when the forecast calls for heavy rainfall, sleet, or hail.

Do this because Mums out in the open, with no protection, wind up drowning from too much rainwater. The vast majority of the damage is to the buds and foliage as well. At the soil level, mulch can serve as a partial barrier to protect the root system.

Unfortunately, for any late bloomer plant in the garden, when adverse weather hits, there are parts of the plant that won’t survive. Golden rule: the more parts you shelter, the easier it will be to nurse them over the winter.

4– Root Rot

Potted Chrysanthemums

Root rot is not limited to just drowning the roots, starving them of oxygen would work too. The biggest concern, however, is fungal and bacteria diseases that latch onto overly moist parts of the plant.

Did you know that potted Mums are more susceptible to root rot? That’s because they are full sun plants that do not fare well in shade. That also means that the soil dries (or should dry) faster, requiring more frequent watering.

Novice gardeners tend to wonder why their Mums are wilting, discover that it is due to a lack of water, so they go and add some more. That can be the case, but more often than not, it is the soil that isn’t optimal for the plant.

In most instances, potted Mums need to be repotted in a suitable container and with more appropriate soil than what the stores supply the plant. That’s usually a highly fertilized soil specifically enriched to force Mums to bloom.

Pro tip, though: What you really need is a super-fast draining soil.

Almost always, newly purchased Mums are root bound when you buy them. So, the best thing you can do with a new Mum is to repot in a better soil for faster drainage, and in a pot 2-inches bigger than the one the plant is in when you buy it. That ensures the roots have room to grow.

5– Overcrowding

Multiple Chrysanthemums

For Mums to survive, they need sufficient root growth. As previously mentioned, repotting in a bigger container will fix that. But what if you’re planting multiple blooming plants in a garden bed? 

With so many varieties of Chrysanthemums, you could plant an entire garden bed of Mums. If you do, best to have at least 18-inches between them to allow room for the roots to become established.

Overcrowding a garden bed can lead to the roots fighting for survival too. When roots of plants have to compete for nutrients in the soil, the usual result is none of them win.

Instead, all the plants in the garden bed do not grow as best as they could do if they were given adequate room.

A small sacrifice of space in garden beds in the first year will result in more profuse flowering in the later years when the root zones become established.

Fungal Diseases that Can Kill Chrysanthemums

Aside from the mistakes you could make above as the Mum’s caretaker, there are some fungal diseases that can creep up on your plant without you knowing. Those, too, will cause it to slowly die – so be on the lookout for the following:

1– Verticillium Wilt

Verticillium is soil-borne fungus infection that is difficult to treat. The wilting differs from what you would expect of a thirsty plant. For instance, you’ll notice yellow veins on the drooping leaves.

The yellowing of the veins is the Verticillium fungal pathogen spreading from the roots up through the plant. The farther it spreads, the less effective nutrients can be delivered.

The result is that the plant cannot get the nutrients it needs from the soil. And here’s what’s even more troubling: 

Verticillium wilt has a high resistance to fungicides. Treating Verticillium wilt of chrysanthemum plants is near impossible. 

Tip: The most reliable method to help some of the plants survive is to take a disease-free cutting and plant in sterilized soil – soil that has been heated to 160℉ for a minimum of 30-minutes.

Effectively, once the fungus is in the plant, it will die. A healthy part of the plant needs to be removed then potted. It’s similar to how you would divide established Mums, only this time, in sterile potting soil.

2– Septoria: Leaf Spot

Septoria is a fungal disease that causes dark leaf spots to appear, sometimes with a yellow halo surrounding the spot. Septoria infections start at the lower part of the leaves then spread upwards.

This disease slowly kills the plants by cutting off its ability to photosynthesize efficiently. It is spread by water, either by directly watering the leaves or by rainfall, causing the pathogens to splash to nearby foliage.

The size of the spots differs, but they can cover up to a third of an infected leaf, at which point the leaf dies. The more leaves that become infected, the faster the plant dies. The longer that goes on, the less chance there is of any healthy leaves surviving. So, move quickly!

The only way to stop the spread of Septoria is a weekly fungicide treatment. Additionally, all infected leaves would be better cut off and disposed of rather than waiting until the leaves drop.

Remember too: Fungal pathogens can overwinter in soil, essentially lying in wait to strike again next season.

3– Pythium: Root Rot and Stem Rot

Pythium is one of the more prevalent types of root rot to infect Chrysanthemums. 

It is considered a plant parasite rather than a fungus. It’s also a water mold that absorbs nutrients. When it latches onto the root systems of plants, the mold grows instead of the plant. The result is a form of root rot and stem rot.

Pythium rot starts at the base of a stem and spreads upwards. Growth of the plant will be stunted; the leaves will discolor and the plant will eventually die if it isn’t treated with a suitable fungicide that specifically targets the Pythium parasite.

When this gets a foothold, prune away diseased parts of the plant, then replant a healthy cutting.

4– Erysiphe: Powdery Mildew

Erysiphe is a type of fungi that causes a powdery mildew to dust the leaves of the plant. Unlike the other fungi we mentioned here, this powder doesn’t need water to thrive. 

Erysiphe produces tiny, powdery spores on the surface of the Mum’s tissues. These spores can spread through the air and land on other plants and Mums around. They then germinate and form new structures whose main job is to suck the nutrients from the plant cells.

The powder will also impact the plant’s photosynthesis, hindering its ability to make food.

How to stop Erysiphe from spreading? Easy! 

Start by providing enough space between the plants so there’s enough circulation. This makes it harder for the mildew to jump around from plant to plant. Water your Mums at the base and not overhead, too, as this keeps the leaves dry.

Final Thoughts

Armed with everything I just gave you, your Mums will no longer risk dying anymore. All it takes is learning the right tips to keep the plant alive and thriving during the winter times.

Make sure to observe your plant as regularly as you can, too. Watch out for the signs I mentioned here and treat problems as soon as they occur.

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