Plant stems turning black is a serious problem. The good news is you can save your plant’s life once you identify the root cause of blackened plant stems.
Stem infections are the most common cause of this problem. Stem rot, bacterial infection, rusting stems, and blight are common in houseplants. Whereas other reasons are pest infestation and some environmental factors. Low humidity, too high or low temperature, leaf infections are easy to treat.
In this post, I will explain
How you can identify the root cause?
What are the Treatments?
How to prevent plant stems from turning black?
What are the root causes of plant stems turning black?
1. Stem rot
Stem rot is the most common reason for black stems. The fungi that cause root rot is responsible for stem rot. It is more common when your plant sits in water-logged soil. The higher percentage of moisture in the room also infects the stems.
The common infection symptoms are softening, stem turning yellow to brown, and then black. Small brown dots on a particular part of the stem.
Black stem means the infection of the advanced stage. There are fewer chances of saving your plant in this case.
Immediately trim and remove the infected stems of the plant. Also, remove other infected parts of the plant like flowers and foliage.
Use fungicides and repot your plant in a new pot in fresh potting soil.
Note: If the main plant stem is turning black. Then use stem cutting or any other method to propagate it. This is the only solution only if the main stem is infected.
2. Bacterial Canker
Bacterial canker is caused by a pathogen called Pseudomonas syringae. In this condition, you see small black lesions on the plant stems. These lesions regularly secrete the watery solution that sticks to the stem and keeps it moist. Your plant stem slowly turns black due to this watery sticky liquid.
This also impacts foliage health. The leaves above the infected part of the stem start turning yellow. In the advanced stage, these leaves start falling off and your plant eventually dies.
Take sharp shears and remove the infected or dead stems and leaves.
This problem is common in spring at the time of pruning. Therefore, apply grafting wax on the pruned stems right after you trim.
The best solution is to use copper sprays to kill the pathogen that is living on your plant.
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There is a group of plant-fungal infections that is called blight. Blight is of 2 type one is early bright and the second is late blight.
In early blight, Alternaria solani bacteria is responsible for blackening the stems. This problem is common in the early days of the active season. This is not a plant disease it is a soil fungus that infects plant health.
Because the bacteria that live in the soil infect the parts of the plant that are close to the soil. This means the bottom parts of the plant.
At first, you see brown spots later they turn black and destroy the stem.
Late blight comes from Sep to Oct. It is also a soil disease that infects the fruit, foliage, and stems close to the soil.
Cut the infected parts
Give support to your plant to increase fresh air circulation.
Do not overwater the potting soil
Use copper fungicides or bio-fungicides to solve the problem fast. Copper-based sprays give quick results.
Do not wet the leaves and stems while watering plants.
4. Rusted Stems
Plants live in warm weather, high humidity, and receive low light. Often get infected by stem rust. This can infect the foliage, flowers, fruits, and almost all parts of a plant.
The symptoms are:
Black spores on leaves and stems
Black spots on leaves, leaves turn yellow
Wilting stems and weak plant growth
Keep the surroundings clean and hygienic
Remove dry and dead parts of the plant
keep the base of the plant clean
Use Sulfur-based fungicides and apply them to the infected parts.
This gray mold is a little hard to kill. It can appear on any part of the plant. Cool and humid places are the ideal homes for botrytis.
Botrytis spores break the leaf protection layer and enter the leaf and stem tissue. They start eating the material in the stem and turn it black.
The gray mold will cover the infected parts and reduces the absorption of light. The covered foliage stats dying due to the low amount of light.
Separate the infected plant from other healthy plants.
Cut the parts that are covered under the mold and through them in the garbage bin.
Change the place of your plant to improve the air circulation
Spray fungicide and let your plant dry and heal
Once it heals properly then you can place it back with other plants
6. Pest infestation
Common houseplant pests like mealybugs, aphids, and scales blackened the plant stems. They suck the sap of the plant. And release a waste liquid called honeydew.
This liquid gets stuck to the stems and causes plant stems to turn black.
When they suck the sap, the plants become weak and stop growing. The sap includes the plant’s energy which is glucose.
When a plant does not have enough to eat it becomes weak and stops growing. This weakens the plant’s natural defense system. Your plant becomes an easy target for diseases.
Wash your plant with insecticidal soap and apply neem oil on the infected parts.
Keep the plant base clean and remove the dead parts.
Prune it regularly to improve air circulation in dense plants.
At last, separate it from other plants
Use professional pesticide sprays if the pest infestation is at an advanced stage.
How you can prevent plant stems from turning black?
To stop plant stems from turning black following are the best practices that you can follow. The main aim should be cleanliness. The following are the key points.
Increase the air calculation in the grow room. Every plant needs fresh air to stay healthy and to achieve good growth.
Keep the area around your plants clean and free from dust and other debris.
Regularly trim your plants.
Always change the growing medium at the time of repotting.
Never use the used growing medium of one plant to grow another plant.
Check the plant needs before buying.
Adjust the temperature and humidity according to the plant’s needs.