Hydrangeas are the most prominent plants in the yard because of their large blossoms. At the same time, these plants sometimes have problems and that is the topic we are going to talk about today.
Iron deficiency causes chlorosis and, as a result, hydrangea leaves turn yellow. The reasons for chlorosis can be high soil pH or root rot.
Too much sun is another reason for the yellowing of the hydrangea leaves. To fix this problem, plant your hydrangea in a spot with 6 hours of direct sun a day.
Below we will look at all the possible causes of yellowing and how to fix it.
Deficiency
The most common cause of hydrangea leaf yellowing is a lack of trace elements in the soil. This results in disruption of photosynthesis and changes the color of the leaves. There are several elements whose deficiencies can lead to negative consequences, let’s look at them.
Hydrangea leaves turning yellow because of nutrient deficiency.
Iron Deficiency
The first element is iron. It is necessary for the development of the leaves and stems of the plant. If it is not enough, chlorophyll production during photosynthesis will be disturbed and a disease called chlorosis will occur.
Chlorosis can occur not only when the soil lacks the necessary elements, but also because the soil is too alkaline or because of root rot. We will talk about these specific cases later in this article.
What does iron deficiency look like in hydrangeas?
Iron deficiency on hydrangeas looks like the yellowing of the leaves between the veins. The veins remain green, but the space between them turns pale at first and eventually turns yellow.
A typical case of iron deficiency can be seen in the photo above. This hydrangea has just begun to suffer from this deficiency and the leaves have not yet turned completely yellow.
How to fix it?
To fix iron deficiencies in the soil, you need to apply iron chelate. This is a form of iron that is easily absorbed by hydrangea roots and is commercially available online or at garden centers. Apply as much iron chelate as the label recommends and do not exceed the rate.
However, you should not expect results too quickly. Also, the yellow leaves will not turn back to green. Only new foliage will be green and healthy.
Nitrogen Deficiency
Next is a nitrogen deficiency. This element is also needed for hydrangeas to have large green leaves. Nitrogen deficiency usually occurs because the soil is too poor.
Symptoms of this problem are yellowing of the leaves, which usually starts at the tips and progresses to the center of the leaf.
How to fix it?
To fix the nitrogen deficiency, you need to add organic matter to the soil near the hydrangea. Good quality compost is best for this. You can also use cow manure, but make sure it’s well-rotted.
Simply mix half a bucket of compost or manure into the soil around the hydrangeas. Try to avoid damaging the roots.
Magnesium Deficiency
Magnesium is an essential element for photosynthesis. Although not much of it is needed, hydrangeas are very often deficient in it.
A symptom of a magnesium deficiency is chlorosis. This means that the leaves turn yellow between the veins, just like with iron deficiency.
How to fix it?
Use magnesium sulfate to fix this. You can buy it at any plant store. Next, dilute the manufacturer’s recommended amount in a gallon of water and irrigate the hydrangea.
Watering issues
Next comes the watering issues. This includes both overwatering and underwatering hydrangeas. In either case, yellowing of the leaves is possible.
Overwatering
Hydrangea leaves turning yellow because of overwatering.
Overwatering is a very common problem with many plants, including hydrangeas. Although hydrangeas are considered moisture-loving, large amounts of water can cause root rot.
A root system affected by rot is unable to absorb nutrients and water. This can cause the leaves to turn yellow.
Causes of overwatering are usually too frequent watering, poor soil drainage, long rains, or a very soggy location.
What does overwatered hydrangea look like?
Symptoms of an overwatered hydrangea include stopping its growth. New leaves and flowers will not appear.
In addition, the leaves start to turn yellow at the tips or edges. Over time, the leaves will fall off. If the weather is hot, the leaf may dry out and turn brown before dropping.
How to fix it?
To fix overwatering, water hydrangeas only when the soil is 2 inches dry. Avoid watering in winter when the plant is dormant.
Make sure the hydrangea has good drainage. Also, avoid planting it where it is very wet. For example, this may be a place where rainwater collects or a place near a pond.
Underwatering
Underwatering hydrangeas can also cause the leaves to turn yellow. If the leaves get enough water, they are able to evaporate it by lowering the temperature of the plant.
But if there is not enough water, in most cases the leaves will wilt. If the weather is sunny and hot at the time, the leaves may additionally turn yellow.
How to fix it?
Water the hydrangea when the soil is 2 inches dry, but no later. Especially closely, keep an eye on soil moisture during hot summers.
Use about 1 gallon of water or more for each plant. Be sure to mulch the root zone with 2 inches of organic matter.
How do you tell if hydrangea is overwatered or underwatered?
The main difference between an overwatered hydrangea and an underwatered hydrangea is that the leaves of the underwatered hydrangea wilt and turn yellow. At the same time, the leaves of an overwatered hydrangea simply turn yellow without wilting.
A clear sign that a hydrangea suffers from underwatering is that the soil around the roots is dry to a depth of more than 4 inches. While a sign of overwatering is very soggy soil.
In addition, the signs of underwatering appear first on the upper leaves. Whereas overwatering becomes noticeable on all the leaves at the same time.
The leaves of an overwatered hydrangea will turn yellow and fall off. In most cases, they can no longer be saved. At the same time, if you water the thirsty hydrangea immediately, the leaves can quickly recover.
Sunlight issues
Hydrangea leaves turning yellow because of too much sun.
Too much sun can cause hydrangea leaves to turn yellow. If we are talking about Hydrangea paniculata, it is the most sun-tolerant and requires some shade only in zone 7.
Hydrangea macrophylla (Bigleaf Hydrangea), on the other hand, is the least sun-tolerant and needs about 6 hours of direct sun a day except for the afternoon sun. Otherwise, it can get sunburned and the leaves will turn yellow.
Also, keep in mind that lack of sun can cause yellowing of the leaves. This usually happens to the lower leaves that get almost no light at all. They turn yellow and eventually fall off.
How to fix it?
Whichever hydrangea you have growing, give it six hours of direct sun. At the same time, it’s best to avoid planting in afternoon sun.
Ask your seller how much sun your particular hydrangea needs. Provide the right amount of sun for it. If necessary, transplant it to a new location.
Diseases
Diseases are another typical problem of yellowing hydrangea leaves. Diseases are divided into viral, bacterial, and fungal. Fungal diseases are the most common cause of leaf discoloration.
Hydrangea leaves turning yellow because of disease.
Fungal diseases
In this case, it all starts in the spring. The fungus spores get on the young leaves of the hydrangea and begin to sprout there. Sometime in the summer, brown spots appear on the leaves and the leaf turns yellow.
Some diseases affect a large part of the leaf and it turns partly brown and partly yellow.
High humidity and poor aeration in the garden will promote the development of diseases.
How to fix it?
Remove the yellowed leaves. Spray the hydrangea with a multi-purpose fungicide. Repeat spraying after two weeks.
Avoid overwatering hydrangeas. Provide good drainage and improve air exchange around the shrub.
Rot Root
Root rot is a fungal disease that affects the roots of the plant. This can happen if the plant is overwatered or if the soil drains poorly. The first sign of root rot is usually yellowing leaves.
If you suspect your plant has root rot, it’s important to act quickly. Remove the affected plant from the soil and dispose of it. Then, amend the soil with compost or other organic matter.
This hydrangea disease can definitely be avoided if you provide the right environment for your plant.
Hydrangea leaves turning yellow because of damaged roots.
The next disease is root rot. In this case, the roots are unable to supply both trace elements and water to the leaves.
As a result, chlorosis can develop and the leaves turn yellow. It is also possible that the leaves will wilt and turn brown.
Root rot can be caused by a variety of factors. In most cases, it is overwatering or poorly drained soil.
But roots can also begin to rot because of damage from planting or transplanting. Or you may have been digging around your hydrangea and damaged the roots.
How to fix it?
Avoid overwatering and only water hydrangeas when the soil is about 2 inches dry. Improve drainage around the roots or transplant the hydrangea to a less wet location.
Avoid damaging the roots when planting or transplanting.
Soil issues
If the soil does not meet some criteria, it can lead to plant problems including yellowing of the leaves. In this chapter, we will talk about the pH of the soil and how drained it is.
Hydrangea leaves turning yellow because of chlorosis.
Soil pH
The pH of the soil is very important because if it is above 7.0, the hydrangea will not be able to absorb iron and other elements from the soil. This will lead to chlorosis and yellowing of the leaves.
The symptoms will be the same as with iron deficiency. The leaves will turn yellow between the veins and the veins will remain green.
How to fix it?
Check the pH of your soil. Use a digital soil pH meter or kits to do this. If the pH is higher than 7.0 you need to acidify it.
Use an acidifier to acidify your substrate. These products are commercially available in a wide range.
Poorly drained soil
Heavy and poorly drained soil is very often the cause of root rot. This, as you already know, leads to the yellowing of the leaves.
In addition, such soils are usually poor in nutrients. This can also lead to problems.
How to fix it?
Before planting your hydrangea, add a few buckets of compost to the planting hole and mix it with the native soil.
If the hydrangea is already planted, spread the compost around the root zone and mix in the topsoil. Be very careful not to damage the roots.
Fertilize twice a year. The first time in early spring and the second time just after flowering. Use a slow-release multi-purpose fertilizer.
Abrupt changes in temperature
Hydrangea leaves turning yellow because of cold snap.
Abrupt changes in temperature are a factor that can lead to temperature stress in hydrangeas. Cold winds make the problem even worse.
If your hydrangea is temperature stressed, its leaves may turn a pale yellow. Sometimes it can lose a lot of leaves as a result.
How to fix it?
Provide a comfortable environment for the hydrangea. If necessary, cover the shrub for the duration of the spring chill.
Eliminate all cold drafts around the shrub. This is especially important if you are in the northern part of the country.
Newly planted hydrangea leaves turning yellow
Newly planted hydrangeas can experience transplant shock and their foliage will turn yellow. This is because you are sure to disturb the root system, which will have a negative effect on the whole plant.
Also, after planting, hydrangeas are very prone to underwatering. The fact is that newly planted hydrangea does not yet have a large root system and is not able to get water from the surrounding soil.
If you do not water it in time, it may turn yellow. On top of that, the new location has a different sun exposure, which also makes the situation worse.
How to fix it?
Put in an extra shade over the newly planted hydrangea for a few months. It’s best that it doesn’t get direct sun during this time at all.
Water it when the soil near the roots is 1 inch dry. At the same time, do not overwater it.
To avoid transplant shock, transplant hydrangeas only in early spring before the leaves emerge. Do this gently without damaging the roots.
People are also asking
Should you cut off yellow hydrangea leaves?
You should cut back the yellow hydrangea leaves. This should be done to prevent the development of fungal diseases. Yellow leaves usually have many fungal spores that can infest healthy leaves.
Cut the leaves in the middle of the leaf petiole to avoid damaging the hydrangea branches. Throw the cut leaves in the trash away from your yard. Always sterilize your pruning tools before and after work.
How should you apply fertilizer when the hydrangea leaves are yellow?
To properly apply fertilizer to yellow hydrangeas, first determine the pH of the soil. If it is too alkaline, use acidifiers to make it neutral or slightly acidic.
If you fertilize with a multi-purpose fertilizer, do it first in early spring and the second time after flowering. Spread the fertilizer evenly around the hydrangea.
If you use magnesium sulfate or iron chelate, you can apply it at any time except in winter. Dilute the manufacturer’s recommended amount of product in a gallon of water. Next, water the soil around the root zone.
Why are my hydrangea leaves turning yellow with brown spots?
The reason why hydrangea leaves turn yellow with brown spots is anthracnose disease. The brown spots appear on the green leaf, but over time, when there are too many spots, the leaf turns yellow and falls off.
To cure hydrangea, remove all diseased yellow leaves to the trash. Spray the hydrangea with a fungicide designed for anthracnose.
Avoid overwatering hydrangeas and water over leaves. Improve air exchange around the shrub.
How do you fix yellow hydrangea leaves?
- Adjust the soil pH level to 5.5-6.5.
- Apply iron chelate and magnesium sulfate.
- Avoid overwatering and underwatering.
- Provide hydrangeas with 6-8 hours of direct sunlight.
- Spray diseased leaves with fungicide.
- Apply a slow-release multi-purpose fertilizer in early spring.
Why are my hydrangea leaves wilting and turning yellow?
Hydrangea wilting and turning yellow due to underwatering. Lack of water causes the pressure in the leaves to decrease. As a result, they wilt and droop. If the weather was sunny at the time, the color will change to yellow.
To fix this immediately water the hydrangea with at least 1 gallon of water. Next, do not let the soil dry out more than 2 inches. Be especially vigilant during dry and hot weather.
Why do hydrangea leaves turn yellow in the fall?
The reason hydrangea leaves turn yellow in the fall is because of the seasonal shedding of leaves. Hydrangeas are deciduous plants and every year they drop their old leaves, but before that the leaves turn yellow.
You don’t need to do anything about it. This phenomenon is a natural cycle and is inherent in all deciduous plants.
The only thing you might want to do is pick up the leaves and throw them away. Don’t leave them rotting in your yard because they can be a breeding ground for disease.
Hydrangea yellow leaves at the bottom
Hydrangea’s lower leaves usually turn yellow due to lack of sunlight. As the hydrangea grows, the upper leaves shade out the lower ones. Eventually, the lower tier of leaves turns yellow and falls off.
To fix this, you need to provide the hydrangea with more sunlight. If all the leaves are evenly illuminated, they will not turn yellow.
At the same time, hydrangeas do not like too much sunlight. So if it has lost only a few of its lower leaves, there is not much point in doing anything about it. The upper leaves will provide energy and everything will be fine.