Zamioculcas zamiifolia (ZZ for short) is native to Africa and dates back many centuries. ZZ has excellent properties for growing in homes and offices.
ZZ plants are easy to grow, easy to care for, drought tolerant, tolerate low light from the sun, and accept artificial light. This plant is slow growing in height, has dark green leaves, and is healthy and very attractive.
Therefore, this plant has become popular in offices and homes around the world. However, a common problem that many people experience is black spots on ZZ plants.
How do I determine the cause of this phenomenon? Is there any way to overcome and limit black spots on ZZ trees? Join us to find the answer in this article.
Black spots on ZZ plant – Causes and solutions
There are many causes of black spots on ZZ plants. One of the common reasons is a disease, insects, direct exposure to light, too much water, or too little water.
You can easily see 2 common types of black spots on ZZ plants: black spots on stems and black spots on leaves.
1. Black spots on the body due to direct exposure to light
If you find your ZZ plant has dark spots on its trunk, you need to check the planting location of the pot. If you grow ZZ plants in an environment with too much light or in direct sunlight, dark spots will appear.
This is completely normal and not a sign of the disease because ZZ plants are suitable for low light conditions. It will thrive in low light like other office plants.
Solution: You just need to move the ZZ plant to a location with less light. The dark spots may be difficult to go away and the plant will also grow slower due to the damage.
Ideally, you should place the ZZ plant in a place with 12 hours of indirect sunlight a day and avoid direct sunlight. The ideal location is near a window and a few steps away is best.
Because ZZ plants do not have to be exposed to direct sunlight, they can still receive the right light every day.
2. Black spots on stem or base
If the black spots on the stem or root appear pasty or humus, it is the stem or root rot. The cause of stem and root rot is often related to water problems.
Stem and root rot is a condition in which the plant is constantly wet, waterlogged, does not drain, and the leaves are always wet. The cause is due to improper watering such as watering from the top of the tree down.
In particular, ZZ plants do not like direct sunlight, so if the leaves and stems are always wet, the fungus will be favorable to attack and cause disease.
Many types of fungal spores are commonly found in the air, soil, and water. They will grow quickly in wet conditions and destroy ZZ plants.
Solution: In fact, when you discover this situation, the ZZ tree has very little chance to respawn. What is important is the degree of stem rot and root rot.
If this is new, you need to gently remove the ZZ plant from the old pot. Use a clean pair of scissors to remove rotten stems and roots. Then you put it in a new pot that has better drainage.
You should move the potted plant to a cool and dry area so that the moisture on the stem and leaves is released. You also need to check daily and water only when the soil is dry.
An important note is that you must water the soil and not wet the leaves to avoid fungal diseases.
To prevent stem and root rot, you need to water properly, water only during the day on the soil, and avoid waterlogging.
3. Black spots on leaves
Black spots appearing on the leaves of ZZ plants can be caused by excess light and leaf burn. As you know, the ZZ tree is native to Africa and lives in tropical forests. So it usually receives very little direct sunlight or no light at all.
The leaves and stems of the ZZ plant are very vulnerable if they are exposed to sunlight for too long. The common condition is leaf burn and the appearance of black spots.
If the black spots appear only on a few spots on the leaves, it is not a cause for concern. However, if the leaves turn brown, yellow, and completely wilted, the ZZ plant is likely to die.
Solution: To overcome this situation, you should not leave the ZZ plant near a window where there is too much direct sunlight.
A distance of 1 meter from the window is the ideal location for the ZZ plant to receive indirect light. For rooms that receive less light, you can move closer to the window and move when the sunlight is stronger.
4. Black spots due to too much watering
Over-watering the ZZ plant is one of the common problems that many people have.
Over-watering causes many problems for plants including brown spots appearing on leaves or stems.
When you water too much, the pot is prone to waterlogging, poor drainage, and reduced oxygen in the soil. In fact, plants need CO2 to absorb and photosynthesize through the leaves, but they also need oxygen to absorb through the roots.
Over-watering will cause the soil to become waterlogged, reducing oxygen levels and root rot.
In addition, the condition of the soil that is always waterlogged and wet will be favorable conditions for fungi to grow and harm plants.
Solution: You need to learn how to water properly and at the right time. A pre-set watering schedule is not an ideal choice. Instead, you need to test the soil moisture before you start watering.
Some factors you need to check are:
- Lift the pot, no overflow or lightweight
- Use your hand to check the moisture in the soil
- The color of the soil, the drier the soil, the lighter the color of the soil
- Use a hygrometer to control humidity every day
If you find your ZZ plant is waterlogged, move it to a new pot with drier soil. If this plant has stem and root rot, remove the rotted parts with clean scissors and monitor daily.
5. Dark spots due to dehydration
If you notice that the ZZ plant has black spots on the leaves or tops, it is dehydrated. Curling, falling leaves, and wilting are early warning signs of this.
This situation will soon be overcome if you detect it in time and water it. To be sure, you need to check the moisture in the soil, and if the soil is dry or watered regularly.
Solution: To limit water loss, you need to water the ZZ plants deeply every week. This plant also doesn’t need too much water per day, so you can water it as much as you need for a week.
You can place the potted plant in the water tray for half an hour or an hour to let the water seep into the potting soil.
In summer, the weather and temperature are high, especially during drought, you need to water more often. In winter, you only need to water once a month to prevent the plant from rotting.
6. Dark spots are caused by too much or too few nutrients
Normally, ZZ plants do not need too much fertilizer and they can grow on their own under normal conditions. However, in order for ZZ plants to grow healthy and green, fertilizer is still essential.
Too much fertilizer will also cause this plant to wilt, soften and appear in brown spots. This can cause ZZ plants to burn their roots and not grow normally.
Solution: To promote plant growth, you only need to fertilize once a month during the growing season like spring and summer. You should use liquid fertilizer and follow the instructions in the ratio.
7. Humidity in the home or office is too low
ZZ plants are native to the tropics of Africa, so they are more tolerant of moisture than many other indoor plants. However, they still need at least 40% indoor humidity to grow healthy.
If the humidity in your home is too low, ZZ plants will develop brown spots on leaves, stems, and roots.
Plants can lose water due to transpiration from leaves, but when the air is too dry, they will gradually dry out, wither and fall off.
Solution: You can use a humidifier to increase the humidity by at least 40% to 50%. You can also use water trays to create humidity in your home.
In addition, planting more trees is also an effective way to create moisture in the air.
8. Black spots caused by fungal and bacterial diseases
ZZ plants are generally known for their intense vitality and good tolerance. However, if they are in bad condition, bacteria and fungi are often easy to attack.
There are many types of fungi that damage ZZ plants such as:
Fungi of the Ascomycete, Capnodium, or Saprophytic families commonly cause brown powdery substances on the entire ZZ plant.
These fungal spores can survive in the air and cause damage to plants. You need to clean and remove brown powdery substances as they can attack and cause dark spots to appear.
Some other common fungi from the families Fusarium, Pythium, Rhizoctonia, and Phytophthora. They often cause root rot, stem rot, and black spots on leaves.
In addition, black spots appearing on the leaves can also be a sign of a bacterial attack. If you’ve killed them with a fungicide that doesn’t work, then bacteria are the culprit.
Currently, there is no cure for bacterial disease. If the ZZ plant has a fungal disease, you need to use a fungicide to kill it.
Solution: To avoid fungal diseases, you need to adhere to the following principles:
- Increase airflow in the home or office
- Reduce the humidity in the air, by not less than 40%
- Do not wet the leaves
- Avoid waterlogging and well-drained soil
How to reduce brown spots
To limit brown spots, it’s important that you know the causes, so you can come up with some standards. ZZ plants are tropical forest plants so they don’t need too much direct light.
With the soil, air, and water characteristics of the varieties from Africa, you need to pay attention to a few things:
- Avoid placing ZZ plants in direct sunlight
- Do not overwater the ZZ plant
- Fertilize once a month during the growing season like spring and summer
- Maintain room humidity at least 40%
- Treats insect and fungal infestations quickly
There are many causes that cause ZZ plants to appear with brown spots on leaves, stems, and roots. Some of the main causes are fungal diseases, bacteria, improper watering, nutrition, and humidity.
To solve this problem, you need to limit direct sunlight and water at the right time and in the right way. Use fungicides to kill early to remove fungal spores.
However, this plant is poisonous and can affect the health of humans and pets. So please consider planting it in a suitable location and use gloves when touching it.