15 Common Problems With Coneflower Plants

Coneflowers are beautiful perennials that fill our gardens with brightly colored flowers all summer long. Coneflowers are easy to grow and are relatively drought-tolerant once they are established in your garden. This makes them an excellent choice for full-sun gardens.

This is a fungal disease that typically affects the leaves. Your coneflower may be suffering from anthracnose if you notice dark lesions on the leaves of your plant. These lesions will grow as the leaf turns yellow. Eventually, the entire leaf will turn brown and die. 

Anthracnose is most common in humid or wet weather. It is also found commonly in areas that are densely planted. 

Using a copper fungicide is the best way to treat anthracnose in coneflowers. Follow the label instructions for application rates. 

Aphids

Aphids are the enemy of every gardener. These teeny tiny green bugs can be found crawling up the stems of your coneflowers in the summertime. They are just about the same color as the stem, making them difficult to see. Oftentimes you will notice the side effects of an aphid infestation before you will see the insects. 

A sure sign of aphid eating is the yellowing of your stems and leaves. If the infestation has gone unchecked for long periods of time, the leaves and stems will weaken and could collapse. Another sign of aphids is the presence of ants.

The ants are not doing any harm to the plant (or the aphids, unfortunately). They are simply attracted to the sweet excrement of the aphids, referred to as “honeydew”. 

Aphids can be sprayed off of your plants with a strong hose stream. You could also use insecticidal soap to get rid of these little bugs. Removal of any infected plant parts can help the spread of the insects and any diseases they may be carrying. 

Aster Yellows

This is an interesting disease spread to coneflowers by leafhoppers as they hop from plant to plant. 

If you have ever looked at the cone of your coneflower and seen something that looks like leaves or tiny green flowers growing out of them, you have experience with aster yellows. The leafhoppers spread this disease when they encounter an infected plant.

As they hop from plant to plant and continue to feed, they infect the plants. You may also notice leaves that are curled and twisted, yellowing of the leaves, smaller and bushier vegetative growth, and flowers that will not fully develop properly. 

Unfortunately, this is a detrimental disease for your coneflowers. You should pull any infected plants as soon as you notice any of the above signs. The best way to prevent this disease is by preventing leafhoppers which can be tricky. Keep your gardens free of weeds as well as other debris that could provide shelter for the leafhoppers. 

Deer and Other Wildlife

Coneflowers are known for being relatively resistant to deer. However, when the growth is young and soft, deer have been known to nibble on coneflowers when they are in need of food. 

I personally have seen rabbits and chipmunks eating the coneflowers in my garden. The rabbits will eat the flowers, stems, leaves, you name it. If you notice that your coneflower stems are suddenly missing from your plant, but are lying on the ground nearby, you likely have a chipmunk dining in your garden. 

If you have trouble with deer eating your gardens it may be worth your while to use deer netting to keep them from getting to your precious plants. These nets are simple to use. All you need to do is lay the black netting over the plants that you are worried about, you may need to use some stakes to keep it in place.

If you have other critters in your gardens, you can use an animal-repellant sprays, some of which can be made of natural ingredients. Spraying these products on your plants will cause them to taste and smell less tasty than the animals are expecting. 

Drooping Leaves 

If you notice that the leaves of your coneflowers are severely drooping or wilting, it is likely that your plants need an extra watering session. This is a common occurrence when the heat of the summer ramps up, and garden tasks start to become overwhelming. 

Drought-ridden coneflowers may have drooping, cracked, dried, or yellow leaves. Other signs that your coneflower needs water are cracked soil around the plant and drooping stems. 

Coneflowers are tolerant of drought once they have become established in your garden. Until then, these flowering perennials need about an inch of water per week.

During the hot summer months, it is wise to use a water gauge in your gardens to make sure that your plants are getting enough water. It may be that you need to supplement natural rain with hand watering or irrigation. 

Eriophyid Mites

Just like other mites found in your garden, eriophyid mites are microscopic insects that will suck the life out of your coneflowers. These mites will cause similar symptoms to aster yellows, causing small growths to bloom out of the cone.

The difference is these growths may show hints of the petal color rather than being green. Check the undersides of the leaves and look for yellow feeding spots and any abnormal contortion of the leaves.

The good news about mite damage is that it is usually just cosmetic. You can remove the mites by spraying your coneflowers down with the spray of a hose. Trim off any affected flower heads or leaves to remove any remaining mites. 

Faded Flowers

When your garden is filled with brightly colored flowers such as coneflowers, it can be so disappointing when the colors begin to fade. Why do they?

Unfortunately, this is just a natural progression in the flower’s lifespan. The petals can fade just from too much sun exposure. Coneflowers thrive in partial to full sun. Oftentimes, full sun combined with drought-like conditions can cause the flowers to fade faster than normal. 

They also begin to fade after they have been pollinated. Pollination sends a signal to the plant that the flowers have done their job, and the plant can begin using energy to strengthen the roots. 

If you do not like the look of faded flowers, the best thing you can do is to deadhead the flowers when they begin to fade. Deadheading is a simple task, especially when you are deadheading coneflowers.

Find the stem that your fading flower is growing on and cut the stem close to the nearest set of leaves. This will keep your plant looking neat and tidy. It will also allow the plant to heal nicely. 

Lack of Flowers

There are three common reasons your coneflower may not produce flowers at the rate you hoped. 

The first is a lack of sunlight. Coneflowers love the sun and need partial to full sun. Anything less than 4 hours of sunlight per day will affect the plant’s ability to produce flowers. If you have planted your coneflower in an area that does not get enough sun, it is very easy to transplant them to a new location.

If you don’t have any areas in your yard that get enough sun, try planting the perennial in a container that you can situate on a patio or step that gets enough sunlight. 

The second is poor soil. Coneflowers grow best in well-draining soil. If you have clay soil, you may have some difficulty growing happy coneflowers. The reason for this is that clay soil will hold too much water around the root system.

This can lead to the weakening of roots to the point of no return. You can amend your soil upon planting by adding in some compost. This will help to break up the dense clay and provide the coneflower with the right soil balance that it needs. 

Finally, the third is using incorrect fertilizer. Flowering plants need phosphorus to promote blooming. Coneflowers do not require much fertilizer at all.

However, if you have been using a basic 10-10-10 fertilizer in your garden, or if the coneflowers are planted near a lawn that is fertilized, it could be getting too much nitrogen. Look for a fertilizer with a higher middle number, such as a 3-4-5.

Fusarium Wilt

This is a fungal disease that is relatively common in our gardens. This fungus causes the plants to take on the appearance of wilting. While it may be common for healthy plants to wilt in the afternoon sun, plants that are infected with fusarium wilt will appear wilted in the morning sunlight as well.

Another symptom you may notice is the edges of your leaves becoming discolored, usually browning. 

Unfortunately, there is not a really good method of control for this fungal disease. Before you do anything drastic, try watering your plant. If it does not bounce back overnight, you can feel confident that your plant is not just drought-stressed.

The best thing you can do is to remove the plant and any nearby affected tissues. You will, unfortunately, lose the plant, but you can save the rest of the plants in your garden by removing the wilted plant. 

Japanese Beetles

If you are a gardener in North America, chances are you have encountered a Japanese beetle or two. These beetles are not picky when they are choosing their next meal. These beetles are easy to identify with their copper wings and bluish-green heads. 

The grubs of Japanese beetles are common on your lawn. If your notice grub trails in your lawn, you can bet on having a large beetle population in the summer. If you don’t have any grub trails, you are not totally in the clear, as the beetles can fly and travel from garden to garden easily.

The feeding sites of Japanese beetles are easy to spot. They will munch on the leaves, leaving large holes. The beetles will leave the veining of the leaves behind, giving the leaves a lacey appearance. 

While the damage of Japanese beetles can appear daunting the good news is that it is manageable. You can fill a bucket with soapy water and knock the beetles into the bucket to remove them from the plant. You can also use a specific Japanese beetle killer available from Bonide. 

Leafhoppers 

These tiny green insects fly around from plant to plant and spread diseases throughout the Asteraceae family. The leafhoppers themselves cannot cause too much damage from their feeding.

However, if they have recently fed on a diseased plant (especially one with aster yellows) they will be spreading that disease around to other coneflowers in your yard, 

Keeping your garden clean from debris over the winter and all season long is a great way to keep leafhoppers from setting up shop in your yard.

Beneficial insects have been known to keep leafhoppers in control. You can purchase beneficial insect eggs online and sometimes at your local garden centers. 

Leaf Spots

When we refer to leaf spots, typically, we are referring to a broad group of fungal diseases that cause discolored spots on the leaves of your coneflowers as well as other plants in your garden. You may notice that the tips of your leaves have brown edges or that you may have circular or irregular brown spots on the leaves of your plants. 

Fungus is spread through the splashing of water. Be it irrigation or rainfall, the spores on the ground or on other plant surfaces nearby a healthy plant will easily splash with water droplets. 

Removing any leaves with brown spots is a great place to start in terms of caring for your coneflowers. Next, use a copper fungicide to treat your plants. This is a broad-spectrum fungicide that can help your plants to recover from any fungus infections. 

Powdery Mildew

Powdery mildew is an extremely common fungal disease found in many gardens. It is more common in shady gardens, but it is just as common in gardens where plants are close together, and there is not a lot of airflow.

If you notice a white or silver fuzz growing on your plant that looks like, well, mildew it is most likely powdery mildew. Occasionally this “mildew” will take on a purple hue. Luckily, this disease rarely damages your plants for the long term. If you leave the fungus untreated, it could distort or stunt the growth of any flower buds. 

Try to prevent powdery mildew by allowing enough space between plants. You can also prevent this disease from spreading by watering the base of your plants.

If needed, you can purchase a fungicide from your garden center that is specified for plants suffering from powdery mildew. Be sure to remove this infected growth from your garden in the fall to ensure that your garden will be fungus free in the spring. 

Stem Rot

Are the stems of your coneflowers turning brown and appearing to rot out? Well, that is likely exactly what is happening.

Because coneflowers like moderately dry conditions, excessive moisture can cause issues within the perennial. You may notice blackened stems that suddenly die. You may also notice leaves and flowers turning black and dying as well. 

Keep an eye on how much you are watering your plants. While you can’t save the rotted stems, you can make changes in your gardening habits going forward. You could be overwatering, or the soil conditions in your garden may be less than ideal for coneflowers. These are both easy enough to remedy.

Keep track of how much water your garden is getting and cut back on hand watering and allow nature to provide irrigation for a bit. When it comes to soil, the best thing you can do is begin to incorporate compost into your existing garden soil. This will fluff up heavy soil and give the roots of your coneflower room to breathe. 

Stunted Growth

Stunted growth can look a little different from plant to plant. The overall plant could be shorter than normal, or it could look weak and less vigorous. 

Frequently, this has to do with a lack of sunlight. It could also be due to a lack of water. If you are noticing that your coneflowers don’t look just right, take a hard look at your care for them.

Ensure that your coneflowers are receiving at least 5-6 hours of sun per day and are getting enough water. If these conditions appear to be in order, take a look at your soil structure and the nutrient breakdown. Having a soil test done is a great way to figure out what your soil may or may not be lacking.