Rhododendron is a shrub plant of the Heather family, characterized by large flowers and dense leaves. A flower is bred as an ornamental plant. Among gardeners, known under the name "Alpine Rose". The species of Rhododendron is very extensive: it includes evergreen and deciduous shrubs, as well as small trees. Heathers are known for their ability to "signal" about diseases and pests: they change the color of leaves. When rhododendron turns yellow, not everyone knows what to do. Experts advise starting with establishing a cause. This will help determine the treatment.
The main causes of yellowing of rhododendron
Rhododendron, like most garden plants, sometimes suddenly turns yellow, so it is important to know what to do in such cases. Most often, this is due to a violation of the rules of care, diseases and pests.
In healthy rhododendron leaves are emerald green
Non-compliance with irrigation rules
One of the reasons why rhododendron leaves turn yellow is a violation of the "technology" of watering. Alpine rose is hygrophilous. Lack of water is fraught with dryness, yellowing and falling leaves. Excessive hydration will also not bring benefits: the root system will begin to rot.
To find out how much moisture a plant receives, you need to take a lump of earth from under the bush. If drops are squeezed out of it, then there is too much liquid. Loose lump indicates a lack of water. Optimum moisture is manifested in the plasticity of the soil: a lump is easily formed from it.
Important! Trees will help maintain the required moisture level. If you plant an alpine rose in the shadow of a tall plant (for example, pine), the water will slowly evaporate.
Rhododendron "loves" acidified water, so it is recommended to mix it with:
- lemon;
- vinegar;
- oxalic acid.
Watering is carried out using a system of sprinklers.
Soil acidification is the key to alpine rose health
Lighting
Rhododendron quickly turns yellow in direct sunlight and "prefers" shady areas. This should be considered when choosing a place for a flower bed.
If necessary, shading is created artificially: the plant is covered with tent fabric or polycarbonate. The ideal option is to highlight an alpine rose in the shade of buildings, shrubs or trees.
Root system damage
Rhododendrons are distinguished by a shallow root system. It can be damaged not only during transplantation, but during weeding, loosening and even overheating of the soil. To prevent yellowing of the leaves, the trunk circles mulch with:
- oak leaves;
- pine needles;
- high peat;
- moss.
The layer height should be 5 cm.
Important! Loosen the soil under the rhododendron with great care. Many gardeners completely refuse such treatment.
Poor quality soil
If the gardener does not know what to do, if the rhododendron has yellow leaves, he needs to start by analyzing the soil.
For proper development, rhododendrons need acid soil: they will not receive useful substances from neutral soil. Horse peat and rotted coniferous litter are traditionally used. The composition of the soil is regulated using citric acid, electrolyte, colloidal sulfur.
Rhododendron only survives on acidic soil
Poor fertilizer
The condition of plants directly depends on the quality of fertilizers.
Rhododendrons turn yellow if you use the following dressings:
- Ash. It reduces the acidity of the soil, which leads to the occurrence of chlorosis. The disease manifests itself in yellowing between the veins of the leaves.
- Superphosphates. This type of fertilizer must be used carefully. Excess phosphate leads to a lack of iron, which provokes the development of chlorosis.
- Chlorine and lime based crust. It destroys the mycorrhiza necessary for acidification of the soil.
- Imported fertilizers in granules. Such drugs are designed for growing rhododendron in hot climatic zones. They stimulate the growth of new shoots in late August, which will die with the onset of winter.
Important! To feed rhododendrons, it is recommended to use seasonal liquid fertilizers. They are better absorbed.
Organic dressings are less effective than soluble
Inflorescences not removed
To alpine rose remained healthy, you need to remove all inflorescences in a timely manner. This will help to avoid yellowing of the leaves and make the “caps” of rhododendron more magnificent.
Inflorescences easily break off hands. The main thing is not to damage the young shoots. In place of old inflorescences, 2-3 new ones will appear, and the leaves will retain a green tint.
Pests can lead to yellowing
To understand why rhododendron leaves turned yellow, you can by examining the bushes. Garden plants are often affected by pests, and an alpine rose is no exception.
Rhododendron bug
The presence of the pest is determined by the change in color of the leaf: first it becomes pale green, then yellowish. The lower part is covered with bedbug excrement. They have the appearance of a sticky substance.
Rhododendron bug close-up
When severely affected by pests, the leaves curl up and fall off.
To get rid of bugs, rhododendron is sprayed with Karbofos or BI-58 insecticide.
Attention! Rhododendron bug can destroy the whole bush.
Mealybug
This pest is similar to tiny lumps of cotton wool. The worm sticks to the outer surface of the sheet and is attached to the internodes. Dry soil and sparse watering provoke its reproduction. Mealybug does not tolerate high humidity.
Important! Before chemical treatment of rhododendron, the pest is removed from the leaves manually. The plant is wiped with a cotton swab dipped in soapy water.
After the initial treatment, rhododendron is sprayed with a systemic insecticide. Confidor and Aktara will do.
The mealybug is easily recognizable by its resemblance to cotton balls
Aphid
One of the most common pests.
Aphid affects the back of the leaves. They gradually turn pale, becoming a yellowish tint.
They fight aphids with the help of Confidor, Actellik, Nurela D.
Aphids in a short time affects the inner surface of the leaf
Black thrips
The pest leaves gray holes at the top of the sheet. Bottom holes with a black edge. The affected areas are covered with brown and gray spots. Sick leaves turn yellow, then fall off.
Organophosphorus insecticides help get rid of thrips. For example, Atom, Fostran, Dishans, Eurodim.
Thrips eat rhododendron leaves, leaving holes in it
Khrushchev
Khrushchev is a Maybug larva.
It damages the root system, making the leaves turn yellow and fall off. In some cases, shoots dry out.
There are many insecticides that can destroy the cartilage. Most popular:
- Anti-crunch;
- Bazudin;
- Actara;
- Zemlin;
- Nemabakt.
Maybug larvae can turn into a real disaster if you do not treat rhododendron in time
"Chemistry" will quickly rid the alpine rose of various pests. The main thing is to take action in time.
What diseases can cause yellowing of leaves
Rhododendrons are particularly susceptible to infectious and fungal diseases. They weaken the plant, destroy the root system, cause yellowing and falling leaves.
Septoria
It is considered the most dangerous fungal disease in rhododendrons.
It manifests itself in the formation of red spots on leaves, rapidly increasing in size. After some time, the marks become pale. The foliage dries up, turns yellow and, finally, falls off.
Attention! If treatment is not started after the first symptoms appear, rhododendron may be left without leaves.
You can overcome the disease by removing the affected part of the bush and treating the plant with a fungicide. For example, you can use Ridomil Gold.
Septoria is easy to recognize by red marks
Chlorosis
Chlorosis often causes yellowing of rhododendrons. The disease is due to a deficiency of nutrients in the soil: nitrogen or iron. Most often, occurs in the spring. Chlorosis is manifested in a change in the color of the foliage: it becomes pale, turns yellow, becomes stained.
Chlorosis is treated with iron chelate top dressing. The most effective liquid means with which you can spray the foliage. Most often, iron sulfate and citric acid are used.
Chlorosis - a typical alpine rose disease
Fusarium
It is a fungal infection of the root system. The disease begins with yellowing, drying of the leaves, and ends with the death of the shoots.
Important! Fusarium infection requires immediate treatment with fungicides. For example, Bactofit is suitable.
Fusariosis provokes drying of foliage
What to do to save the plant
To understand what to do when the leaves of the rhododendron fade or turn yellow, you need to determine the cause. To begin with, evaluate how much moisture a plant receives. Rhododendron reacts immediately to abundant and scarce watering. Watering an alpine rose should be moderate.
With an infection of the plant, the damaged parts of the bush are carefully cut, and the leaves are treated with an insecticide on both sides. In some cases (for example, with chlorosis), treatment is supplemented with fortified dressing.
It is equally important to monitor the acidity of the soil.
Important! Indicators should correspond to 3-4.5 pH. If necessary, the soil is acidified.
In addition, there is the possibility of soil rejection during transshipment. To avoid this, an earthen lump is shaken from the roots. If the plant "does not like" the soil, the roots will not go beyond the old coma and the rhododendron will die.
What is the danger of yellowness of leaves
The color change of rhododendrons may be due to natural causes. For example, the onset of autumn. In this case, sanitize and remove dried leaves.
Autumn alpine rose changes the color of leaves
Yellowing in the warmer months is a bad sign. It can be caused by a fungal disease or the appearance of pests. Stains and damage to the leaf indicate a serious condition of the plant. In this case, you can’t do without moving the flower bed to a shaded place. It is necessary to treat the rhododendron with a chemical agent, after removing the diseased foliage.
Important! The "unplanned" yellowing of the rhododendron is fraught with the death of young shoots and the bush itself. A change in color indicates a deficiency of nutrients, a low level of soil acidity, mechanical damage and dangerous diseases. Therefore, this symptom cannot be ignored.
Prevention
As you know, it is easier to avoid unpleasant consequences than to deal with them.
Prevention of yellowing of foliage in rhododendrons is as follows:
- Moderate regular watering.
- The location of the flowerbed in a shaded place (in spring and summer, the alpine rose is especially sensitive to the sun).
- Maintaining the required level of soil acidity (within 3-4.5 pH).
- Daily spraying of leaves.
- Watering the plant with antifungal drugs and preventive treatment from garden pests.
- Refusal of loosening the soil and removing weeds: the root system is close to the surface.
Thus, in order to understand why the leaves of a rhododendron fall or turn yellow, it is necessary to analyze the living conditions of the plant. Creating a favorable environment in the country is very easy. If you properly care for the rhododendron, it will delight flowering for more than one year.
