Underwatered Cactus: How To Identify, Treat and Prevent It

By | Updated on November 2, 2023

Are your cactuses not doing so well? If you think they may be underwatered, read on to learn how to identify and fix the problem.

Cacti are known for their ability to go long periods without water and still survive.

However, this is only true if they have been cared for properly up until that point.

In this article, we will discuss how to identify the symptoms of an underwatered cactus and ways to treat them so that they can thrive again.

What Are the Risks of Underwatering a Cactus

Underwatering and overwatering are both common problems when it comes to indoor plants.

In the right conditions, a cactus will thrive and bloom with vibrant colors that can brighten up any room.

An underwatered cactus is a cactus that has not been given enough water, either because you’ve consistently watered it too infrequently or because it has been grown in less-than-ideal conditions. 

While this may not initially seem like a very big problem, the consequences of underwatered cacti can be severe and long-lasting.

The consequences of underwatered cacti can include:

Stunted Growth or Complete Failure To Grow 

This is because water plays a significant role in photosynthesis.

If your plant isn’t getting enough water, it will not produce chlorophyll and cannot carry out normal processes like converting carbon dioxide and sunlight into glucose.

This is the most severe consequence of underwatered cacti and can be irreversible in many cases.

If your plant’s growth has been stunted due to insufficient water, it may simply never grow again at all, even after proper watering practices are resumed.

Dehydrated Cactus (Drought Stress)

Underwatering a cactus does not always result in death or permanent damage; instead, when this happens, plants will often lose their green coloration and appear “dull” for a while before finally recovering with fully hydrated roots.

However, over time these periods of dehydration take a cumulative toll on the plant’s health until there is noticeable lasting damage which cannot be reversed by additional watering alone.

Root Rot

If your cactus is kept in an area with poor air circulation and too much moisture, this can result in root rot.

The roots of a cactus that has been left underwater for too long become infected by various forms of fungi and bacteria.

Like dehydration, these infections are usually fully reversible as soon as you resume proper watering practices.

However, if they have progressed far enough to cause permanent damage, there may be some lasting effects on plant health even after treatment has begun.

Root Loss or Death 

The most extreme consequence of underwatered cacti occurs when all water supply to the roots is cut off entirely.

If this happens, the roots’ cells will become dehydrated and die; if enough of these cells die, the entire root system (and consequently the plant itself) may rot and eventually fall apart entirely.

This is a very serious condition that can be fatal to cacti – but it’s also completely preventable as long as you take care not to allow your plants to dry out too much between waterings.

How Does Underwatering a Cactus Occur?

If you are new to growing cactus plants, it is easy to make mistakes like underwatering.

They require very little water compared to other houseplants and succulents, but there is a right and wrong way of doing things.

The most common mistake people make is to water their cactus too infrequently.

The frequency with which you need to water your cacti depends on where it’s being kept and the type of potting soil mix it has been planted in, but generally speaking, they should be watered once a week at most during warmer months.

During wintertime, when there are no growing cycles taking place, reduce watering until spring comes again.

If you live in areas with high temperatures year-round, these plants can take more frequent showers if needed without causing any damage or stress-related problems because the heat will dissipate much faster than for those living near coasts or other cooler climates.

The only time you should water your underwatered succulent is when the soil feels dry to the touch.

By this, we mean it won’t take long for a finger inserted into the top couple of centimeters of soil to feel dry enough to warrant watering.

If you wait too much longer than this before giving them a drink, they will become stressed out and more difficult to revive as time goes on if their droopy appearance continues without being watered back up again.

Once you have watered your cactus, wait a few days and check if it needs more water.

If the soil is still moist to touch after this time frame, hold off on watering until next week when they should be ready for another drink.

How To Tell If Your Cactus Is Underwatered

It may be difficult to tell if your cactus is underwatered.

Underwatering usually occurs gradually over time, so the cactus will not look drastically different from day to day.

However, there are a few signs you can look for to determine if your cactus is underwatered.

Signs of an Underwatered Cactus

It is essential to know the signs of an underwatered cactus so you can take action early on. This will increase the chance of your cactus recovering.

The most common signs of an underwatered cactus are:

The Cactus Is Light Green or Yellowish

When a cactus is underwatered, it will lose its dark green color.

This usually occurs gradually over time, so the change in color may not be noticeable at first.

You can look out for other signs of an underwatered plant if your cacti start to turn light green or yellowish.

The Spines Are Falling off Easily

When a cactus is well watered, its roots extend deep into the soil and absorb water.

However, when underwater, their root systems do not function properly because the lack of nutrients in the soil causes them to die back.

This leads to weak spines that fall off very quickly – another common sign of an underwatered cactus. 

The Cactus Is Wilting

Wilt is another sign of an underwatered cactus.

Their spines cannot hold up the plant properly due to a lack of nutrients, causing them to lose their form. 

This causes plants that were once upright and firm in shape to become limp or droopy over time.

Decay at the Base of the Plant

When roots cannot absorb enough nutrients from the soil due to lack of water, they will stop growing and start deteriorating over time, leading to decay at the base of the plant.

This usually happens gradually, so you may not realize right away if your cacti are underwatered or not.

The Cactus Spines Turn From Black to a Light Brown Color

When a cactus is underwatered, its spines turn from a dark black or brown color to a light brown.

This usually occurs gradually over time, so the change in color may not be noticeable at first.

You can look out for other signs of an underwatered plant if your cacti start to turn light green or yellowish.

The New Growth on Your Cacti Is Weak and off Center With Older Growth

When a cactus does not have enough nutrients, it will affect how it grows new limbs. 

In this case, you’ll notice that newer growth is somewhat malformed, and they’re less symmetrical than older ones – another sign of an underwatered cactus.  

How To Save an Underwatered Cactus?

The best way to determine whether the cacti you have is underwatered or not is by checking the soil.

If it feels dry and hard when you squeeze it between your fingers, then chances are its roots are dying back due to lack of water. 

Once you’ve identified that your cactus needs more water, make sure to follow these steps:

Water Thoroughly but Do Not Overwater 

It might be tempting to give them a lot of water all at once because they look like they’re in dire need.

However, overwatering cacti can lead to root rot if you overdo it – something that’s almost impossible for the plant to recover from.

Water Them Every Two Weeks During the Winter and Once a Week in Summer 

Watering frequency depends on how hot it is where you are located – hotter climates require more frequent watering than cooler ones. 

For example, if your cactus gets three hours of sunlight or less per day, water around one to two times a month throughout the year.

However, if they receive six hours of sun exposure daily, then aim for twice-weekly watering until fall when temperatures cool down again.  

Use Soil That Drains Well So Excess Water Can Seep Out Freely 

Water thoroughly and allow water to drain out freely. 

Cacti tend to do best with fast-draining soil, allowing excess water to flow through quickly so they can absorb it as needed.

Many commercial cactus soil mixes are available for this very purpose these days – look for one with sand or perlite added to the potting mix. 

This will help improve the drainage of your cactus roots, which also helps prevent root rot from forming when you overwater them.  

Use a Container With at Least One Bottom Drainage Hole 

Make sure there is at least one drainage hole on the base of their container so excess water can seep out easily without getting trapped inside, where it could cause root rot instead. 

This is especially important if you are planting them in a clay pot with no holes on the bottom.  

Water Deeply but Do Not Water Frequently 

Watering frequency will depend entirely on how much sunlight your cactus gets daily. 

If they get at least three hours of direct sun exposure, then water once every two weeks during winter and once a week throughout spring/summer when temperatures rise again to prevent wilting.  

However, if they’re getting less than that (or none), try watering around once or twice monthly, depending on their size.

Smaller plants can be watered slightly more often, while larger ones need less frequent watering until fall comes again.

Repot the Plant in Fresh Soil if Necessary

An underwatered cactus may need to be repotted in fresh soil if its roots are dying back too much. 

This will help promote new growth and make your cactus healthier overall – another sign of an underwatered plant is stunted or deformed new shoots.  

Repotting them can also improve drainage, making it easier for the excess water they take in to flow out freely.

How To Prevent Underwatering a Cactus?

To prevent underwatering a cactus, it is essential to understand how often you should water a cactus plant.

Watering frequency can vary depending on the cactus species you have and where it is located.

Some of them can be watered for a few days after drying out completely, while others require watering every week or two.

However, the best way to know how often you should water a cactus plant is by checking the soil.

If it has dried out completely, you need to water it. If the soil is still wet, do not add more water until you are sure that it has dried out completely.

To water a cactus properly, add the water when it is sunny and allow all of it to dry out completely. You can repeat this process for about a week or two before watering again.

To prevent underwatering, it is also important to consider the location. Cacti do better in warm, sunny locations, so it is best to place them where sunlight reaches them for most of the day.

This helps with water evaporation and prevents underwatering a cactus plant.

Final Thoughts

An underwatered cactus is not receiving enough water from the environment. 

This can be for various reasons, but most commonly, it stems from caretakers believing cacti need less water than they do and watering them accordingly. 

When watering a cactus, it is important to be mindful of the amount of water supplied.

Too much water will lead to rotting, and too little can cause damaged roots that cannot be undone.

For this reason, it is essential to be able to identify signs of underwatered cactus.

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