Dieffenbachia leaves turning yellow – cause and treatment methods

Dieffenbachia is extremely popular among gardeners. This plant belongs to its own genus, belonging to the Araceae family. There are over 60 species of this flower in the wild, many of which are grown indoors.

Dieffenbachia is distinguished by its thick, robust stem, which can reach several meters. Large, oval-shaped leaves are located on the stem. Although the plant can flower, its leaves are its ornamental value.

Leaf blades are most often multicolored (green, white, yellow), but there are also species with solid green leaves. Most species have spotted spots on a green background, but some have stripes, borders, and a prominent midrib.

Over time, the lower leaves fall off, exposing the trunk. This deprives the dieffenbachia of its aesthetic value, so the flowerhead must be cut off and rerooted. Most members of the species have a single apical point. However, breeders have succeeded in producing hybrids with dormant lateral points, allowing the plant to bush out.

The most common difficulty gardeners encounter when growing dieffenbachia is yellowing leaves. The main reason for yellowing leaves is improper care of the dieffenbachia.

Care errors as the main causes of yellowing leaves in dieffenbachia

Dieffenbachia isn't fussy, but it's also far from easy to maintain. The plant immediately reacts to unsuitable growing conditions by changing the condition of its leaves. Yellowing leaves are often associated with improper care. This can include inadequate lighting, temperature, humidity, watering, as well as improperly selected fertilizer, soil, and potting soil.

Lighting

Dieffenbachias are sensitive to direct sunlight. This causes yellow-brown spots—scorch marks—on the leaves, which eventually lead to death. Yellowing and leaf drop also occur with insufficient light. The plant should be kept in partial shade in summer and on a windowsill in winter. This is the only way it will receive the necessary amount of light.

During the warmer months, when the sun is particularly strong, shade the plant with a curtain or place it near a window. It's best to place the pot on the east, west, or north side of the room. This location will protect the plant from the sun's harmful rays.

During colder months, cloudy weather prevails. To provide the plant with the necessary light, it is moved to a windowsill. In this case, it is best to move the flowerpot to the south side of the house. If this is not possible, dieffenbachias can be provided with supplemental lighting using fluorescent lamps.

Temperature and humidity

The plant is very heat-loving. Low temperatures can cause the leaves to turn yellow and eventually fall off. During the warmer months, keep the plant at a temperature of 20-30°C. From September to March, the dieffenbachia enters a dormant period. During this time, the temperature is gradually lowered to a maximum of 15°C.

The plant requires high humidity. Optimal humidity is 65%. If humidity is insufficient, dieffenbachia leaves begin to turn yellow. This yellowing begins at the tips. The lower leaves change color first, followed by the upper leaves. Eventually, they fall off, exposing the trunk.

In addition to mandatory misting, experts recommend using additional methods to increase humidity, especially during winter. The dieffenbachia pot can be placed on a tray filled with damp pebbles. A special humidifier can also be placed near the plant.

Watering

Dieffenbachia, like most houseplants, is wary of overwatering. Excessive watering can trigger rot, which can cause the plant to not only turn yellow but also die.

During the growing season, the plant should be watered as needed. Experts recommend not using a set schedule, but rather moistening the soil as it dries out. In winter, watering should be reduced slightly. During this time, the dieffenbachia is dormant, so it doesn't require many nutrients. Cold water can trigger a negative reaction. For watering, warm the water to room temperature.

Fertilizers

Yellowing of the leaves may be a result of improper fertilization. Dieffenbachia is very sensitive to soil composition. A deficiency or excess of minerals in the soil is accompanied by yellowing and leaf drop.

Finding the right balance is easy if you follow the experts' recommendations. Dieffenbachia should be fertilized only during the active growth period, from March to September. Fertilizer should be applied every three weeks. The recommended dosage should be halved. For dieffenbachia, use mineral fertilizers designed for ornamental foliage plants. It's crucial that the fertilizer be lime-free.

Priming

Yellowing leaves are often caused by improperly selected soil. First of all, it's important to remember that this plant absolutely cannot tolerate alkaline soil or lime. If the plant is removed from such soil, it should be immediately repotted into a more suitable soil, otherwise, instead of a lush flower, you'll end up with just a trunk.

When repotting, it's crucial to warm the soil to room temperature. Transplanting is done by transshipment to avoid damaging the plant's fragile roots. Dieffenbachia will also respond to damage to its root system by changing the appearance of its leaves.

The pot is not large enough

Yellowing of the lower leaves and stunted growth indicate that the pot is too small. Dieffenbachia has a very developed root system. It grows rapidly during its first five years. Therefore, young plants need to be repotted annually, while mature plants need to be repotted every two to three years.

With each repotting, the pot gets progressively larger. A good rule of thumb is to add a couple of centimeters to the diameter of the previous pot. The pot's shape isn't particularly important. If the pot is wide, the root system will grow outward; if it's deep, it will grow downward.

There have been cases where dieffenbachias became cramped in their pots even with regular repotting. In such situations, the plant should be repotted unscheduled into a larger pot.

Diseases and pests of dieffenbachia that cause yellowing of leaves

Yellowing can also be caused by more serious reasons, such as pests or diseases.

Pests

Dieffenbachia can be attacked by aphids, scale insects, and mealybugs. But the most damaging pest is spider mites. After an infestation, small brownish spots appear on the leaves. Over time, these spots grow, and the leaf turns yellow, becomes deformed, and dies. A fine webbing is visible on the underside of the leaf blade and on the petiole. If you look closely, you can see moving brown dots—the mites.

Some gardeners recommend treating the mites by treating the above-ground parts of the plant with hot water (around 40°C). Others recommend treating the plant with a concentrated solution of laundry soap. However, the most reliable way to get rid of the parasites is an insecticide.

Fungal diseases

The most common fungal diseases that cause yellowing and wilting of leaves are anthracnose, root rot, and leaf spot. These diseases can be identified in the early stages by the following symptoms:

1. Anthracnose. Black-brown spots with a yellowish border on the leaf edge.
2. Root rot. Dark spots on the root collar (the part of the plant stem near the base) and a light gray coating on the roots.
3. Spotting. Rapidly expanding brown spots with an orange border.

All of the above diseases can be successfully treated with fungicides. The number of treatments depends on the severity of the infestation. Plant parts damaged by the fungus must be destroyed.

Viral

Viral diseases include bronze disease and mosaic disease. These diseases can be identified by the following symptoms:

1. Bronze spot. Yellow spots on the leaves in the shape of a circle or ring. These leaves wilt but remain attached to the stem.
2. Mosaic. Numerous yellow and green spots appear on the leaves. The plant's growth and development suddenly stops.

Viral diseases are very dangerous for plants and are considered incurable. A plant can contract the virus from a neighboring plant or from harmful insects. Plants with the above-mentioned diseases should be destroyed, and the pot and its location should be disinfected.

Bacterial

Bacterial blight is one of the most dangerous plant diseases. While it's incurable, it can spread quickly, infecting neighboring crops. The first symptom is the formation of water-soaked, yellowish patches with well-defined borders. As the disease progresses, these patches darken, turning brown.

Bacterial disease leads to the death of the plant. To prevent the spread of bacteria, such plants should be burned. The pot and the area where it was stored should be disinfected.

Frequently Asked Questions

Yellowing is one of the most common problems when growing dieffenbachia. It can be caused by care errors or by diseases and pests. It's important to review your plant's care principles and diagnose it for common diseases.