It can be frightening when the leaves of a beloved plant begin to turn red. The good news is that red leaves are usually the plant’s stress response to something in its environment. If you know what is stressing your plant, you can take steps to fix the problem.
Hydrangea leaves turn red from stress. This is usually caused by extreme temperatures, both hot and cold. When exposed to these extremes, the plant produces anthocyanin pigments that protect it in various ways and help prolong the life of the leaves.
I’ll walk you through the most common reasons hydrangea leaves turn red and give you some ideas on how to return them to their lush green glory.
Causes of Hydrangea Leaves Turning Red and Dying
anthocyanin pigments
In most cases, when hydrangea leaves turn red, it is due to the production of anthocyanin pigments in the leaf cells. Plants produce these pigments in response to many different sources of stress, including extreme temperatures, too much or too little light, and when attacked by pests.
There are over 600 species of naturally occurring anthocyanins, and scientists are still struggling to understand exactly how they protect plants.
Studies show that they act as a kind of sunscreen against harmful UV rays, increase the efficiency of photosynthesis and act as antioxidants, protecting against free radical damage.
The solution
The only way to Preventing plants from producing anthocyanins means ensuring that they are not under stress. For hydrangeas, that means planting them in rich, well-drained soil, watering them well but not soaking them, and making sure they get sun in the morning but plenty of shade during the hottest part of the day. .
When growing in the ground, they do not require feeding but will appreciate a compost mulch once a year. In a pot, a slow-release fertilizer specially developed for hydrangeas is a good option.
cold climate
In cool weather, hydrangea leaves usually turn red before they drop from the plant. It is a natural part of the life cycle and is generally not a cause for concern.
Hydrangeas are deciduous. This means that in autumn its leaves die before growing back in spring. During the winter, a deciduous plant is dormant, which means it doesn’t grow and doesn’t need a lot of water or food.
Before falling from the plant, the leaves of deciduous plants produce less chlorophyll (the chemical responsible for the green color of plants) and more anthocyanins.
So, as the chlorophyll fades, we see more orange and red colors appear. This allows the leaves to remain productive as long as possible towards the end of their life.
The solution
There’s no way to prevent deciduous hydrangeas from shedding their leaves in the winter, but they’ll do well outdoors unprotected unless the temperature drops below 0°F (-17, 7°C). In the spring, they will produce new growth which should be green, not red.
Some types of hydrangeas are evergreen, which means they don’t blush in winter or shed their leaves. If you want a plant with bright green leaves all year round, you can go for the climb. hydrangea integrifolia That is seemani hydrangea A try.
grow in full sun
Hydrangeas do best if they get plenty of sun in the morning when temperatures are cooler and shade in the afternoon.
If your plant is in full sun all day, it will protect itself by producing anthocyanins, which cause the leaves to turn red.
These pigments protect the leaf cells from damage and are not harmful, although they indicate that the plant is not in the desired situation.
The solution
Be sure to place the hydrangea in a location where it receives direct sunlight in the morning, but not in the afternoon. Most strains like around 4-6 hours of sun per day, some strains need more or less.
If you can’t move the plant, consider ways to provide it with some shade during the hottest part of the day. You can plant other trees or shrubs or use some kind of structure like a fence to provide shelter.
lack of light
Hydrangeas growing in too much shade can also produce red leaves because the anthocyanins can increase the cells’ ability to photosynthesize. So if your plant gets less than 4 hours of sun per day and turns red, that could be the problem.
Lack of light usually causes a pale growth that leans towards the nearest light source or, in some cases, a combination of pale and red growth.
The solution
Make sure your plant gets enough sunlight. If it’s in the shade, move it to a brighter spot while making sure it’s not in direct sunlight.
If you can’t move the plant, consider ways to increase the amount of light it receives in the morning, such as cutting other nearby trees and shrubs.
phosphorus deficiency
Hydrangeas don’t eat much, and too much fertilizer can reduce the number of flowers on the plant or even damage the root system. However, if you see the lower leaves of your plant turning purple from the tips, that’s a sign of phosphorus deficiency.
One thing to keep in mind is that when soil temperatures drop below 55°F (13°C), hydrangeas have a hard time absorbing phosphorus.
This problem is exacerbated by wet soil, which also makes it difficult for the plant to absorb nutrients. Therefore, it is essential to keep your plant in a well-drained situation.
Keep in mind that in winter most varieties of hydrangeas go dormant and don’t need nutrients, so you don’t have to worry about soil temperature preventing phosphorus uptake. in autumn and winter.
The solution
Use plenty of high-quality compost when planting your hydrangea and apply a compost mulch once or twice a year. Compost contains all the nutrients the plant needs in an easily accessible form.
Unless your soil is seriously deficient in nutrients, you probably don’t need to use fertilizer. However, if you want supplemental fertilization, use a fertilizer developed for hydrangeas and apply it once or twice a year according to directions.
Submarine
The word “Hydrangea” comes from the Greek words for water (hydros) and pot (angos). This should give you an idea of the watering needs of the plant!
Although hydrangeas don’t like wet soil, they do need plenty of moisture. This can be a tricky balancing act for even the most experienced growers!
If you notice your plant’s leaves drying out, curling and turning red, it could be a sign that it needs more water.
Be careful though: before watering more, make sure the plant is not suffering from root rot, as this can also cause symptoms of dehydration.
The solution
Once you have determined that the plant does not have root rot, it is easy to fix this problem. Simply water your plant more!
In the summer, you should probably water two or three times a week. Consider using hardwood mulch to help the soil retain water.
The soil should have good drainage, as hydrangeas do not like wet feet and are prone to root rot. Water less in winter and only when the soil is completely dry.
Xanthomonas and Cercospora leaf spot
If you notice red or purple spots gradually spreading from the lower leaves of your hydrangea, it may be Xanthomonas or Cercospora leaf spots.
Xanthomonas is a bacterial disease and Cercospora is a fungal disease, but both have similar symptoms. They spread from infected organic matter and can be quite difficult to deal with once they take hold.
Bacteria or spores are usually carried from contaminated material to the plant by splashing water, such as rain or when plants are watered from above, but it is also possible that these infections are transmitted through equipment or even by hands. (Source: Michigan State University Extension)
The solution
Try to prevent both infections by removing dead leaves and other decaying organic matter from around the plant. This ensures that there are few places for bacteria or fungal spores to hide, reducing the risk of infection.
Once established, a Xanthomonas infection is difficult to treat. There are no effective bactericides available, so the best thing to do is to remove the infected parts of the plant and hope for the best.
Some plants survive infection; some don’t. If the infection is very serious, it is better to destroy the plant.
Cercospora leaf spot can be successfully treated with fungicides if you notice the infection early. If less than 20% of the plant is infected, chances of survival are high.
For heavily infested plants, it’s probably best to destroy them and try again. Be careful not to reuse soil and pots of infected plants without first sterilizing them.
Phytophthora root rot
The Phytophthora fungus that causes root rot thrives in moist soil and is easily spread by splashing water or contaminated soil.
It is a killer for all plants and can be a particular problem when growing hydrangeas due to its water requirements. If your plant is in soggy soil, chances are it will develop root rot.
Root rot often causes symptoms of dehydration because it prevents the plant from absorbing water through the roots. If your plant has droopy, dry, reddened leaves but gets a lot of water, the problem may be root rot.
The solution
Always make sure your hydrangea is in well-drained soil. Never let it sit in soggy ground for long periods of time. Consider moving the plant or improving soil drainage if the situation becomes soggy.
Once rooted, root rot is very difficult to treat. You can try removing the infected roots, which look brown and slimy, repot them in well-drained soil, and leave them unwatered for a while.
The plant can recover. However, root rot is a death sentence for many plants and it may be best to throw the plant away and try again.
Should You Worry About Hydrangea Leaves Turning Red?
Since red leaves are a symptom of stress, they are often a sign that the plant is not happy with its situation. Although this is not necessarily a cause for concern, you should try to find out what is causing the problem and then you can decide what to do about it.
For example, red leaves in the fall are normal and do not require treatment. However, red foliage from too much sun is a sign that your plant will be much happier elsewhere. And red leaves caused by root rot mean the plant needs immediate attention.