Dahlias are renowned for their gorgeous blooms, so it can be disappointing and frustrating to find that the flowers and leaves are turning brown. There are a number of reasons why your Dahlias leaves and flowers are turning brown, and while the damage itself is not reversible, you can still save the plant and prevent future browning.
The most common reason Dahlia leaves and blooms turn brown is undesirable environmental conditions. To save your Dahlia leaves and flowers, water consistently, provide 6 to 8 hours of sunlight, ensure temperatures are over 60°F (15°C), provide well-draining soil, and treat your plant with neem oil or fungicide.
Why are Dahlia Leaves Turning Brown?
The most common reason Dahlia leaves turn brown is due to a watering issue or poor growing conditions. Dahlias prefer to have at least 6 to 8 hours of full sun daily and are not tolerant of cold soil temperatures.
They prefer evenly moist soil, protection from strong winds and adequate fertilizer that is low in nitrogen levels. Therefore, if your Dahlia leaves are turning brown, it is most likely due to an environmental problem that needs addressing.
Dahlias are tuberous flowering plants that will die back in the winter and reemerge in the springtime. They are members of the Asteraceae family, which means they are related to other popular flowering plants, including sunflowers, daisies and chrysanthemums.
If your Dahlias are planted in soil and have turned brown after a frost event, the plant has begun to die back for the season. Unfortunately, you will not be able to revive the leaves and blooms after that frost event, but fortunately, those Dahlias will return the following year for you to enjoy, so do not panic.
Dahlias are very intolerant of cold soil temperatures. While you can start Dahlias indoors in containers, if you are excited to get a head start on the growing season, be careful not to plant them too early. If you have planted your Dahlias too early, when the soil temperature has not reached at least 60°F (15°C), your Dahlia leaves will turn brown, and the plant will die back due to cold damage.
Dahlias also require a rich, well-draining soil mixture with a pH of 6 to 7.5. If your Dahlias are planted in too dense soil that does not drain effectively, their leaves turn brown due to overwatering and root rot. Root rot occurs when the roots start to deteriorate after sitting in soaking wet soil for prolonged periods of time.
Ensure the soil is damp but never soaking wet, as this can cause the roots to form lesions. Those lesions will allow bacteria and fungus to infect your Dahlias, causing the leaves to turn brown.
If your Dahlias are turning brown due to their soil conditions, the best solution is to switch out the soil immediately. However, if the root rot is severe, you may want to remove your Dahlias from the soil and trim any black, squishy or odorous roots before repotting them.
Make sure that your Dahlias are planted in a well-draining soil mix. Avoid watering excessively in the spring or during cooler temperatures, as it will take them longer to absorb the water from the soil. When your Dahlias are dormant in the winter, it’s best to avoid watering altogether, so the tubers do not rot.
Dahlias ideally need 6 to 8 hours of sunlight each day to grow consistently. So if your Dahlia’s leaves are turning brown and perhaps you are struggling with flower production or flowers turning brown, sunlight could be the culprit.
If your Dahlias are receiving too little sunlight, your Dahlias will experience stunted growth and bloom production due to a lack of nutrients. Sunlight plays a crucial role in photosynthesis; without it, your Dahlias will slowly start to die.
In addition, existing blooms will turn brown and drop off the plant, which will halt the production of new flowers. In this case, you will want to transplant your Dahlias to a place where it receives up to 8 hours of sunlight each day, preferably morning sun.
If your Dahlias are receiving too much sunlight or sunlight that is harsh during the summer heat, you may notice brown patches forming on the leaves, which could result in a sunburn. If you live in a climate with extreme heat and powerful sunlight, consider moving your Dahlias to a location that receives partial shade or protecting them. Opt for morning sunlight, where the sun is gentler.
Why Are My Dahlia Leaf Tips Turning Brown?
If your Dahlia leaves are turning brown starting at the tip, the issue is most likely underwatering. Dahlias are quite thirsty plants, and during the hotter summer months, they may require water several times a week to keep the soil moist. If your Dahlias are underwatered, they will develop brown, crunchy leaves beginning at the leaf tip and slowly moving inward toward the stem.
The best solution for an underwatered Dahlia is to give it a thorough drink and monitor its conditions. Make sure that the soil is evenly moist, but after giving it a drink, make sure that you monitor your Dahlias and the soil conditions over a few days.
If the soil takes a while to dry out again, it could mean that some of the roots have dried out and died off, so it’s best to avoid watering again. On the other hand, if the soil dries out quickly, make sure to water it again.
How Often Should I Water Dahlias?
You should give your Dahlias a drink when the soil is nearly dry but not completely dry. The general rule of thumb is to water Dahlias once weekly during the spring and 2-3 times per week during the summer months.
However, monitoring the soil conditions and watering your Dahlias when the soil is no longer moist is important. Many factors could lead to your Dahlias needing more frequent watering, such as hotter temperatures, sunny locations, and higher humidity levels.
A moisture meter is an excellent tool if you are unsure how often to water your Dahlias, as it can read the soil conditions down to the plant’s roots and will tell you if the soil is wet, moist, or dry.
How Do I Bring My Dahlias Back to Life?
If your Dahlias are in rough shape and rapidly turning brown, your best bet is to prune any brown leaves, stems, and flowers. If they are turning brown due to their environmental conditions, you will want to remove them from their current environment and give them conditions best suited to their needs. This may mean removing any salvageable parts of the plant and repotting it in a container that can access optimal conditions.
Why Are My Dahlia Blooms Turning Brown?
While Dahlia blooms will turn brown if they live in undesirable conditions, they could also be brown due to a pest or disease. Dahlia blooms are equally as attractive to many types of pests, including spider mites and thrips. Their tender, vibrant flowers are typically the first to turn brown.
If you find that your Dahlia blooms are turning brown before they even open or come to the natural end of their life cycle, you should immediately investigate, as it can be a sign of trouble.
If your Dahlia blooms are turning brown along with the leaves, it could be a fungal problem. Dahlias can get fungal infections from airborne spores, but also if the plant has been damaged in some way, creating an open wound on the plant. One particular fungal problem that affects Dahlia blooms is Botrytis blight, which will turn the flowers brown and crispy and may also affect some of the leaves.
Dahlias can also be susceptible to powdery mildew, which primarily affects the leaves and stems, but it can also turn the blooms brown as a side effect. Finally, if your Dahlias are suffering from an infection of some sort, either bacterial or fungal, they will halt bloom production as they enter survival mode.
If your Dahlias blooms are turning brown unexpectedly and you suspect it could be a fungal problem, you can treat your plants with a topical fungicide, which you can purchase at most garden centers. You can also use neem oil to treat fungal infections.
It’s important to prune any affected portions of the plant and to treat only after sunset, as some chemicals may react with intense sunlight and burn your plant. When planting Dahlias, ensure adequate space between them so there is enough airflow. This will help minimize the travel of fungal spores.
If a brand-new bloom is mysteriously turning brown, your Dahlia may have a pest problem. Both spider mites and thrips are very difficult to spot with the naked eye due to their size, but both can cause tremendous damage to your beautiful Dahlias, especially their blooms.
Spider mites can often be recognized by their infamous thin, silk webbing that they create between stems or under leaves. They will feed off the chlorophyll on your Dahlias and completely drain them of their energy. Spider mites thrive in dry, hot conditions, so it’s good to keep a close eye on your Dahlias during particularly hot, dry days.
To treat spider mites, you can blast the adults away with a hose and then use neem oil to treat your Dahlias after sunset. Unfortunately, you may have to repeat treatments a few times before completely eliminating them.
Thrips are small, thin insects that create puncture wounds in the plant to devour its nutrients. They are particularly keen on new growth, blooms, or tender parts of the foliage. So if your flowers or any new growth appear to emerge already damaged, it is a good chance that thrips are the culprit. You can treat thrips similarly to spider mites. However, they are much more challenging to get rid of and tend to spread quickly.
Other types of insects may be drawn to your Dahlias, from slugs to earwigs to even caterpillars. To prevent pest problems, it’s always a good idea to keep your garden area clean and well-weeded, prune any dead or dying foliage and periodically treat your Dahlias for pests as a preventative measure. However, if your Dahlias are healthy and given optimal growing conditions, they should easily withstand minor pest problems.
Should You Cut Off Dead Flowers on Dahlias?
If the flowers on your Dahlias have reached the natural end of their life cycle, it is a good idea to prune them off the plant. Not only will it help keep pest problems or fungal problems at bay, but it will also help to encourage more blooms to form.
Known as deadheading, you can also prune flowers and keep them for yourself, which will also help encourage more healthy blooms to develop on your Dahlias.
It can be unnerving to find that your beautiful Dahlias are starting to turn brown or their blooms are browning and dying back, and there are many reasons why this can happen.
Your Dahlia leaves and flowers may turn brown due to cold temperatures, over or underwatering, too little or too much sunlight, fungal diseases, or pests like spider mites or thrips. To save your Dahlia leaves and flowers, water consistently, provide 6 to 8 hours of sunlight, ensure temperatures are over 60°F (15°C), provide well-draining soil, and treat your plant with neem oil or fungicide.
This will ensure you prevent future leaves or blooms from turning brown so your plant can continue to produce healthy leaf growth and beautiful flowers.