Why Are My Cactus Spines Turning Brown?

If you suddenly notice that your Cactus spines are turning brown, you might start to worry, as often any change in your plant’s appearance might indicate a sign of problems. However, the reason your Cactus spines are turning brown may surprise you, as they don’t necessarily mean that your plant is struggling. 

If your Cactus spines are turning brown with no signs of foliage damage, it might simply mean that the Cactus is aging and maturing, but when combined with other symptoms, brown spines could signal watering issues, soil incompatibility, or pests. 

The best way to find out why your Cactus spines are turning brown will be to look at other symptoms. If there are other signs that your Cactus isn’t doing well, such as the foliage turning brown in addition to the spines, this will indicate that there could be other problems. 

Why Are My Cactus Spines Turning Brown?

Spines Turning Brown Due to Old Age

As many varieties of Cacti age, their spines can slowly start to turn brown, as this is part of the aging process. If you have an older Cactus and notice a few of the spines turning brown and no other symptoms of stress or damage, there is likely no need to panic. Many varieties of Cacti will see their spines change colors over their lifetime.

What Color Should Cactus Spines Be?

The color of your Cactus spines is often not indicative of the health of your Cactus. As most Cacti varieties age and mature, their spines will turn reddish brown, but there are many types of Cacti with spines ranging from yellow to black. 

Some common colors for Cactus spines include:

  • Yellow
  • White
  • Black
  • Red
  • Brown
  • Gray
  • There are even some varieties of Cactus with spines that appear pink

Suppose you notice your Cactus spines are turning unusual colors with no other apparent symptoms of distress. In that case, your best bet is to research the particular variety of Cactus that you have to find out the color of its spines once it reaches maturity. 

Spines Turning Brown From Direct Sunlight

Cactus brown spikes
Cacti grow spines for many reasons, but spines can create some form of shade for some varieties. While most needles don’t produce plentiful shade, a Cactus will undoubtedly take what it can get, particularly during prolonged drought. 

This means that the spines are the last method of protection. While not harmful, sunlight exposure can cause your Cactus spines to change color and turn brown. If your Cactus gets full sunlight and you notice the spines turning brown and no other indication that it is unhealthy, this will likely be the reason. 

Cactus Spines Turning Red

Like many other houseplant varieties that will see their leaves turn reddish-purple in direct sunlight, particularly Hoyas and different succulents, there are plenty of Cactus spines that will start turning red from the sunlight. If your Cactus has a few spines turning red but is otherwise happy, it could indicate that the sun is changing the color of the spines. 

My Cactus is Turning Brown at the Bottom 

If your Cactus is turning brown at the bottom, both spines and foliage, this will indicate that your Cactus is unhappy, and you will need to address the issue quickly to avoid losing your Cactus altogether. 

High Humus Content

If your Cactus spines are turning brown at the bottom and you notice some discoloration on the base itself, this could indicate that your soil is too high in humus content.

Humus content refers to organic compost matter in the soil from other decaying plant or animal matter. If you are someone who likes to add additional compost to your plant’s soil, you may notice that your Cactus spines and even foliage turn brown at the bottom. 

Cacti prefer a more balanced soil pH with a balanced N-P-K ratio (Nitrogen Phosphorus Potassium), and soil that is high in humus content will often have a higher nitrogen content. However, while high humus content can be good for many plant species, it can damage plants that are sensitive to too much nitrogen. 

Therefore you may find that high humus content will turn your Cactus brown at the base, including the spines. Humus content can also be too dense for Cactus roots, making them more susceptible to overwatering and root rot. 

If you notice this happening, you should first change out your Cactus soil. Choose a mixture with plenty of drainage. Avoid adding compost or excessive nutrients to the soil mix and fertilize your Cactus with a highly diluted balanced mixture with an N-P-K ratio of 6-6-6, and only do so during the growing season. 

Overwatering and Rot

An overwatered Cactus with root rot may also turn brown at the bottom, including the foliage and spines. Cacti store water in their foliage, and when they aren’t receiving enough sunlight or don’t have enough drainage, the roots may be sitting in wet soil for too long, causing them to rot. 

What Does an Overwatered Cactus Look Like?

An overwatered Cactus can present in a couple of ways. This rot can spread upwards to the base of the Cactus and cause discoloration ranging from brown to black. The Cactus may start to turn mushy, develop brown or black spots, or the foliage can turn bright yellow. All of these signs can indicate that the foliage is dying. 

What are Signs of a Dying Cactus?

Dying cactus
If your Cactus foliage is turning brown along with the spines, the foliage is dying. It can spread to the rest of your Cactus if you don’t act quickly. 

Here are some signs to look out for:

  • Bright yellow foliage
  • Brown or black spots forming on your Cactus
  • Your Cactus is mushy, moldy, and unable to hold itself upright from a rotted base
  • Your Cactus is turning gray

How Do You Fix Browning Cactus?

If your Cactus foliage is turning brown along with its spines, how you treat it will depend on the reason for the browning. If it is turning brown due to being overwatered or developing root rot, you should immediately remove it from the wet soil and inspect the roots.

You may need to trim away any rotting roots, and if the foliage is severely brown, you may have to propagate pieces of your Cactus depending on the variety and start over. 

Cactus Turning Brown at the Top

Underwatered Cactus

If your Cactus spines and foliage turn brown toward the top, and these brown patches appear dry, this may indicate that it is underwatered. However, if your Cactus is incredibly parched, the dehydrated portions will affect the tip of the Cactus first. You may even notice both the leaves and spines turning yellow. 


If your Cactus is developing brown foliage and spines in various areas and not exclusively at the bottom of the plant, you should inspect it for pest problems. One particularly dangerous pest for Cacti is spider mites, particularly red spider mites

These mites will feed on the chlorophyll of plants, which can cause them to change color. They will mainly go after new growth, which is why you may find spider mite damage at the top of your Cactus rather than the bottom. This type of browning will appear dry; if left untreated, these mites can destroy your Cactus and spread to other plants. 

If you suspect your Cactus has pest problems, isolate it immediately and treat your plant with insecticidal soap or neem oil. If you treat your Cactus with neem oil, keep it away from the sunlight for a while, as neem oil can react to the sun and cause your Cactus to burn. 

How Do You Tell If a Cactus is Over or Under Watered?

Sometimes the symptoms of an overwatered Cactus appear very similar to an underwatered Cactus. If the overwatering is so severe that root rot has occurred, this prevents the roots from delivering water to the rest of the plant. 

If you notice your Cactus turning brown and suspect watering is the problem, the best way to determine whether it is overwatering or underwatering is to check the soil and roots. If the soil is soaking wet and the roots have rotted, you will know it is overwatering. If the soil and roots are bone dry, then giving your Cactus a thorough drink will solve the problem.


While Cactus spines turning brown isn’t always an indication that the entire plant is in trouble, it’s good to check in on your Cactus when you notice any changes occurring to ensure that there aren’t any other signs that it can be struggling. 

If your Cactus spines are turning brown with no signs of foliage damage, it might simply mean that the Cactus is aging and maturing, but when combined with other symptoms, brown spines could signal watering issues, soil incompatibility, or pests.

A Cactus turning brown at the bottom may indicate a high humus content in the soil or root rot from overwatering. A Cactus turning brown at the top may be due to underwatering or spider mites.

Most of the time, spines changing color can be a natural part of owning a Cactus, but if you notice any foliage damage, then there likely will be other factors turning the spines brown.