Why is My Cactus Turning Yellow? 5 Reasons + Fixes

Cacti are remarkably hardy plants, but you can’t rule out some challenges. When stressed out, a cactus will easily change its texture or color. A yellowing cactus may signify incorrect watering, sunburn, inadequate lighting, pest infestation, or transplant shock.

You can help your plant recover and thrive by identifying the cause of your Christmas cactus’ yellowing leaves and taking appropriate action. In this guide, I have highlighted various solutions to issues linked to this problem.

Why is my cactus turning yellow?

A yellowing cactus isn’t just unsightly but a sign of distress due to the following reasons:

1. Incorrect watering

Although cacti are drought-resistant plants, they still need to be watered appropriately. Cactus always prefer the soil to dry out between each watering. Watering too often or not providing enough water can harm or kill the plant.

Cactus turning yellow is a common sign of underwatering or overwatering. Excess water in the soil stops oxygen from reaching the plant roots, thus causing them to suffocate and die. Additionally, root rot fungi thrive in waterlogged soil.

This condition spreads fast, and without early intervention, the cactus turns squishy and eventually dies.

A cactus will also turn yellow and wilt when not provided with enough water. The plant won’t manufacture and transport sugars, a process that entirely relies on water. You’ll notice black brittle roots when the cactus is severely dehydrated, indicating the root cells’ death.

How to save your plant

Saving an underwatered cactus is quite easy compared to an overwatered one. Simply water the plant thoroughly until you see excess water coming through the drainage holes at the bottom of the pot. The cactus should take less than a week to recover.

If you suspect overwatering, let the soil dry out completely. Before watering again, ensure the soil drains well, and the pot’s drainage holes are working. If there is no change within a week, remove the plant from the soil and inspect the roots.

Cut off the damaged roots, wash the plant, and let it sit for two days. Then repot it in fresh soil, specifically one designed for succulents. You may use the same pot, but ensure to clean it first using a solution of bleach.

Pro tip: Water your cactus when the soil is completely dry, and don’t let it sit in any standing water.

2. Inadequate lighting

Light is essential in photosynthesis, where plants make their own food. Without sufficient lighting, a cactus may turn yellow, leggy, and stunted. Most cacti plants thrive in a full day of direct sunlight, but a few species, like forest cacti, prefer only bright indirect light.

If you suspect inadequate lighting, you can restore your cactus’s health by placing it in a spot where it receives at least 4 to 6 hours of direct sunlight. Put it on your brightest windowsill, preferably a southeast-facing window.

Be sure to rotate it every time you water to avoid the cactus leaning on one side due to phototropism. Alternatively, use grow lights where natural light is not sufficient.

3. Sunburn

While cacti plants prefer longer hours of direct sunlight, the high intensity may scorch the plants resulting in a yellow tint on their stems. This problem is common in new plants from a greenhouse, particularly those introduced to high-intensity sunlight without acclimation.

Unfortunately, it is usually not easy to fix cactus sunburn. The plant may heal itself in the right growth conditions. Always acclimatize plants from shady regions before introducing them to the full sunlight intensity. Simply introduce them to filtered light and then a few hours of direct sunlight.

4. Pest infestation

Although rare, cacti and succulents do get occasional insect pest infestations. Insect pests such as scale, mealybugs, and spider mites are known to damage the cacti plants as they suck juices. This typically causes yellow spots on the cactus stems.

Pests are also vectors for infections, and severe infestation may cause the death of the plant.

Controlling pests on cacti plants can be difficult as they are small and hides in places that are difficult to see, explains Missouri Botanical Garden. Some of them, like mealybugs, create a cottony covering that protects their eggs and young ones from insecticides.

Good cultural practices can help prevent pest infestations on houseplants. Be sure to grow your cactus in its recommended conditions, including light, water, and soil drainage. Inspecting the plants regularly and keeping the pot clean will also keep your plants free of pests.

To get rid of mealybugs on cacti or other pests, wash them off with a strong stream of water. Remove any visible pest insects using cotton swabs dipped in alcohol. You may also strictly use recommended insecticidal soaps or agricultural oils as the manufacturer directs.

5. Transplant shock

Repotting a cactus plant into fresh soil solves critical problems such as root rot, pests, and stunted growth. However, improper procedures may lead to failure. Using incorrect soil, transplanting a stressed plant, or incorrect watering can shock the plant.

Yellowing or bronzing of tissues is the first sign of transplant shock. Later, the discolored tissue dries out and turns brown, explains Paul C. Pecknold, Extension Plant Pathologist at Purdue University. However, transplant shock in plants is something that can be prevented.

When repotting the cactus, avoid disturbing the roots as much as possible unless you are dealing with root rot. Pruning the plant before transplanting may also help reduce the shock. After transplanting, the plant should be watered thoroughly and kept away from high-intensity sunlight.

There is no sure way to cure a transplant shock in cacti or other plants. Just wait patiently as you care for the plant. Within no time, the plant will recover from the shock when the roots establish in the new growth media.

Final Thought

Cacti are naturally vibrant plants; you can easily tell when something is amiss. The discoloration of stems or leaves can signify distress due to underwatering, overwatering, pests, incorrect lighting, and improper planting.