6 Reasons Your Cactus is Turning Yellow and How to Fix It

Reviewed by Debra LaGattuta

Hardy, adaptable, and quirky cacti species make interesting additions to your home’s decorative plant collection.

However, contrary to popular belief, these low-maintenance succulents can’t just be left on any old shelf and be expected to thrive.

When growing a cactus indoors, be water-wise, sunlight-savvy, and discerning with drainage. If you see your bright green cactus turning yellow, this is usually a warning sign that something isn't right with their care.

Identifying possible causes for the discoloration and making adjustments right away can sometimes be enough to save your plant.

Other times, if parts of the plant are still healthy, it might be best to propagate a new plant from that section so you can nurture a new healthy cactus under ideal conditions.

Learn more about why your cactus is turning yellow and strategies to salvage it.

1. Improper Watering

Irrigation errors are the most common and often deadly reason for your cactus turning yellow. Cacti are typically drought-tolerant, desert-dwelling species that like arid conditions.

If your cactus is developing a brown base and is yellow further up the stem, you could be unintentionally drowning it.

Once root rot sets in, it’s difficult to save an overwatered cactus.

While overwatering is a common killer, cacti can get dehydrated. This can also cause them to turn yellow.

Suggested Solution

Generally, allow the potting soil to dry out fully between waterings and do not let it sit in standing water.

Once you start seeing wrinkling or thinning plant stems, this is usually a sign it needs a drink. Severe dehydration can lead to root death, but it can take months for this to happen.

That’s why underwatering rather than overwatering cacti is a safer bet. However, if all roots reach the stage of being brittle and black, your plant might not recover.

2. Inappropriate Light

Cacti are generally slow-growing, sun-loving species that need a minimum of 4 to 6 hours of sunlight per day and ideally up to 12 hours to thrive.

However, every species is different, and exposure to too much intense sun (especially for species such as forest cacti) can lead to yellow scarring or splotches because of sunburn.

As this worsens, the yellow spots can turn brown and kill all or part of the plant.

This tends to be more of a problem outdoors. Typically indoors, the challenge is providing enough light; sometimes, you might need to use indoor grow lights.

Suggested Solution

You can use a shade cloth to create bright but indirect light conditions when the scorching sun is at its most intense. It’s also a good idea to gradually acclimate new cacti to their sunny spots.

3. Poor Drainage

Don’t plant your cactus in a standard potting soil. These succulents need a fast-draining medium to thrive and potting mixes specifically designed for cacti are easy to find in garden center, plant nurseries, or home improvement stores.

If the water doesn’t move through the potting mix fast enough, this can also lead to root rot and yellowing of the plant.

Suggested Solution

Use a ready-made cactus soil or mix up your own for better aeration. A typical blend ideal for cacti is three parts potting soil, three parts sand or gravel, and two parts perlite or pumice.

3. Nutrient Deficiencies

Indoor potted plants can sometimes suffer from nutrient deficiencies that lead to your cactus turning yellow.

Suggested Solution

If you have a rootbound plant growing out of the existing pot, repotting makes it easier for the cactus to absorb soil nutrients effectively.

The fresh mix will also be higher in nutrients than the old blend.

While outdoor cacti don’t typically need fertilizer, fertilizing indoor varieties once a month during the plant's growing period can be beneficial.

Where possible, use a fertilizer specifically intended for cacti that contains more phosphorus than nitrogen.

4. Pest Problems

Cacti aren’t prone to many major pest problems, but if insects such as spider mites (which thrive in dry conditions), aphids, mealybugs, or scale infest the plant, it can result in yellow spots on the stem as they suck out the sap.

Suggested Solution

Regularly inspect your plant for signs of pests. If you spot them, don’t delay in taking action. A few insects are much easier to eliminate than a full-blown infestation.

Sometimes, it’s enough to wash away the insects with a blast of water. You can also or spray the plant with neem oil or insecticidal soaps being careful to spray undersides and topsides of the foliage.

5. Transplant Shock

Transplanting a cactus isn’t too tricky. These hardy plants are relatively forgiving.

However, when repotting or planting in a new garden position, minimizing stress reduces the chance of transplant shock, which can turn your cactus yellow.

Suggested Solution

Minimize root disturbance, gently acclimate to bright conditions, and wait a week before watering to settle the roots.

6. Freeze Damage

If there’s an unexpected cold snap, freeze damage can lead to your cactus turning yellow. Less than a few hours of exposure usually only damages the outer layer of the plant.

Prolonged exposure to a hard freeze results in death.

Suggested Solutions

Overwintering your cactus indoors or in a greenhouse protects your plant from cold snaps. If freezing temperatures are certain, it’s best to grow cacti indoors.

Frequently Asked Questions

What does an overwatered cactus look like?

A yellowing stem is not the only sign you are overwatering your cactus. If you see the plant going from firm to mushy and drooping on the stem and spines, this is a sign to cut back on irrigation. The yellowing usually happens further up the stem, with the base of the plant turning brown.

How often do you water a yellow cactus?

If root rot hasn’t fully overtaken your yellowing cactus, let the plant dry out before restarting a more conservative watering regime. You might only have to water your yellowing cactus once every two to four weeks, or even less in the winter. Watering frequencies vary depending on the cactus species, home conditions, and the season.

Can you revive an overwatered cactus?

Whether you can revive an overwatered cactus that has turned yellow depends on whether root rot has fully set in. Once root rot takes hold, the plant's roots will be brown and mushy, and the inner stem can smell bad once broken open. You can try removing mushy, black roots and any rotting stem or leaf parts and repotting the plant in fresh, dry soil, but the damage might be too far gone.

Read the original article on The Spruce.