Why Is My Cactus Losing Needles

Cacti have spines sharp enough to hurt a person or an animal. While this is obviously a downside of owning a cactus, the spines add a look that not many other houseplants can replicate.

However, just like humans, cacti start to show signs of poor health; one of these signs is losing their needles.

To learn more about why this happens, here are some reasons cacti lose needles.

Reasons Cacti Lose Needles

Pest Infestation

The mealybug is the most common bug that contributes to making your cactus lose spines. They are white with a cottony texture.

If you see white substances over your cactus, dry the plant, and remove it from the pot. Check the roots for white cottony substances. Mealybugs like hiding in the roots.

Mealybugs feed on the sap of the cactus, resulting in spine loss. If left untreated, they kill the plant.

The nematode is another pest harming your cactus. It is incredibly small, which means it’s able to stay hidden from most plant owners. Besides spine loss, a nematode infestation in your home in the USA can cause root swelling and discoloration.

The best thing to do to deal with such an infestation is to quarantine the affected cactus and disinfect it with an isopropyl solution.

Mix 70% isopropyl alcohol with 30% water, and spray the plant and its roots. Repeat the process every two to three days if necessary.


Your cactus plant might be suffering from malnutrition if you haven’t repotted or fertilized it for a few years. A severe lack of potassium can result in spine loss.

To fix this problem, you should use fertilizers with low nitrogen and higher potassium levels. Cacti do well if fertilized during their growth days.

Now, when it comes to the topic of fertilizers, you have a number of fertilizer types available to you; however, liquid fertilizers are the best. Just remember to dilute them before using them on your cacti in the USA.

Another option is slow-releasing fertilizers. They keep feeding your plant for months. The best time to fertilize your cactus is between April and August.

Underwatering and Overwatering

If you place your cactus in a sunny spot, it will eventually require water, especially during its growth period.

While watering your plant is a great way to keep it healthy, you should avoid overwatering it. Let your cactus dry before watering it again. The containers you use should have drainage holes in them to better facilitate this process.

If you live in a colder area, the worst thing you can do is keep your cactus from going through dormancy, especially during the winter.

The right temperature range for your cactus in colder regions is 55–59 degrees F. You must water it once in four to six weeks, but allow it to dry before you water it again.

Keeping your cactus outdoors or by your radiator and giving them less water causes root loss. However, keeping them indoors and overwatering them is also problematic.

Your cactus shrinking alludes to underwatering, while plump stems and leaves are signs of overwatering, so maintain a balance.

Less Sunlight

Inadequate sunlight usually happens when your cactus is native to a hotter region, and you reside in a colder area with scarce sunlight.

While some like shade, most cacti like sunlight to grow properly. The lack of sunlight results in spine loss.

Even tropical cacti need bright, filtered sunlight. Keep your cactus in a dim area for a short time. Expose it to filtered, indirect sunlight to help the plant grow and stay healthy.

Turning It Too Frequently

Cacti don’t like to be moved too much, especially when they are about to bloom. If you find your cactus leaning, you can turn it so the other side receives its share of light.

However, don’t turn them if they are about to grow flowers. By turning them during the blooming period, you will affect their blooming, affecting their roots, which further results in spine loss.


It’s common for plants to rot, and cacti in the USA aren’t an exception. If your cactus has started rotting, the spines might start falling.

Your cactus may suffer from dry or wet rot; both are bacterial or fungal growth products.

Wet rot makes your cactus appear mushy and soft. Conversely, dry rot makes your cactus appear dry and discolored. It also starts corking up from the bottom to the top.

Check for rot by pressing the cactus just a little (be careful of the spines). If there is some resistance left, it is a good sign. Moreover, examine the roots to see if there is anything unusual. Replace the soil if you see anything wrong with the roots.

Now, with disinfected scissors, cut the unusual parts of the roots. Wait for a week before watering your cactus, and place it under the sun before bringing it in.

Physical Damage

The least common reason for spine loss in cacti is physical damage. Pets and other small animals are the common culprits of physical damage.

Physical contact can damage the spines and make them fall out, especially when they come into contact with fur.

Some plant dealers sell cacti with fake flowers glued to their needles. The spines get damaged at the spot where the hot glue is used to attach the flowers.

Try to remove these fake flowers, but if you fear damaging the spines, let them come off on their own.

The damaged spot won’t regrow the affected needles, but it will eventually heal, keeping your cactus and the remaining needles intact.

Why Are Needles Important for Cacti?

They Trap Air

The spines on cacti help reduce water loss, and the only way cacti can do that is by limiting the airflow around them.

The needles on your cactus minimize the airflow, thus reducing the amount of evaporation. The air trapped around the cactus creates a buffer zone containing moist air.

Plants lose sufficient water as it evaporates off their leaves, which is where spines come in handy.

They Collect Water

In foggy regions, the spines collect the fog, which drips onto the ground. The roots absorb this fog water.

While most deserts don’t have fog, some, like Chile’s Atacama Desert, do. Coastal fog in Atacama is so common that it even has its name. The locals call it camanchaca.

If there is hardly any rain, but mornings are foggy, the cactus will use its spines to collect all the water it needs.

They Offer Shade

The spines on a cactus plant are fairly tiny, and one can’t help but wonder if they can provide ample shade to the cactus plant.

The truth is, they do. A cactus plant has millions of little needles, and collectively, they provide just the right amount of shade a cactus needs.

Some cacti also have grooves and ridges that multiply the shade these little needles offer.

They Keep Predators At the Bay

Some desert herbivores, like camels, love to munch on the cactus plant. These animals break down the plant to eat the moist sponge residing within.

Spines keep these animals away. The spiniest species of cactus is the cholla cactus. This plant keeps plant eaters like the desert tortoise, pack rat, bighorn sheep, and javelina at bay.

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What To Do If Your Cactus Loses Spines

First of all, stay patient. Needles are an essential component of the cactus’s body. The plant will try to repair the damaged stems if these needles are damaged.

As long as the cactus shows signs of health and growth, new areolas will appear, resulting in new stems and spines growth.

Patience is key as cacti grow slowly. As a result, you will have to wait for a few weeks or even months to see the new areolas grow.

However, you can speed up the growth by properly watering and fertilizing your cactus. Make sure not to overwater or underwater your cactus, as either can result in rotting. Also, too much fertilizer can stress the plant, while too little fertilizer can cause malnutrition. Furthermore, ensure to give your plant ample sunlight, and try not to turn them too frequently, as that also results in spine loss.