Why Is My Cactus Turning Brown?

Cacti are durable house plants requiring relatively low maintenance. Sometimes, the cactus plant tends to turn brown. Generally, it is a sign of ‘corking.’ It is the natural aging process of the plant and causes a formation of brown bark on the exterior. It is not a cause of concern. However, if the browning affects the health of the plant, preventive measures need to be taken.

Why Is My Cactus Turning Brown?

The following are some of the common reasons which lead to the browning of the cactus –

• Root Rot
• Frost
• Sunburn
• Pests & Parasites

1. Root Rot

If the cactus starts turning brown from the base, it is most likely a case of root rot. Root rot happens when the plant is overwatered and there is a presence of stagnant water left behind. It prevents the roots from absorbing essential nutrients from the soil and eventually leads to its death.

Solution

Root rot is a very serious problem as the signs only start showing at an advanced stage. The best way to save the cactus is to cut off the affected roots and treat the plant with the relevant fungicide before being re-potted in a tub with proper drainage and refilled with fresh, fertile soil.

2. Frost

Excessive frost can cause severe internal damage to the cactus. It causes the plant to turn brown. It happens when the plant is kept outdoors in extreme cold, causing the cells to rupture. Browning can also happen when the plant is kept in an air-conditioned environment or near cooling objects such as refrigerators. The plant tries to self-heal by creating calluses over the damaged areas, thus, making it look brown.

Solution

Cactus is highly susceptible to cold. The cactus should not be exposed to temperatures below 10 °C for a long period. Thus, the plant should not be kept outdoors in chilly winters. Similarly, placing the plants near open doors and windows should be avoided.

3. Sunburn

If the cactus starts browning from the top, it generally is caused by sunburn. It happens if the cactus kept in shade for a long time is exposed to direct sunlight. It causes severe tissue damage and requires immediate assistance.

Solution

While permanent sunburn is irreversible, milder sunburn can be treated by moving the cactus to a shady area and regulating the amount of sunshine it receives every day.

4. Pests & Parasites

Different types of pests and parasites can affect the cactus and cause it to brown.
Scales are small, brown bugs that feed on the essential juices of the cactus; making it look brown. Mealybugs are tiny, grey bugs that suck out the sap of the plant and cause severe damage.

Similarly, red spider mites are tiny reddish spiders that accumulate on the underside of the cactus joints. They tend to cause brown, rusty spots in the plant.

Solution

These pests can severely weaken the plant and cause it to brown. The affected plant needs to be immediately isolated and treated with the relevant pesticide. The plant should be kept away until it has healed entirely. The healed plant should be re-potted with fresh, sterile soil before being introduced to the other plants. Further, deterrents such as rubbing alcohol can be used to prevent such infestations.

So, these are some of the steps that could help you nurture your browning cactus back to health.