Signs of Underwatered Cactus (And How to Revive It)


The myth that cacti need very little to no water for survival is very harmful and has led to many cacti plants dying. Just like any other plant, cacti also need your regular love and care and you will surely notice if your cactus is lacking water. If you suspect that your cactus is dehydrated, don’t worry, take a look at this article and find out what you can do to help it. 

The most common signs of an Underwatered cactus are Shriveling, Brittle roots, and discoloration of leaves. In addition, dry brown spots, cactus spines drying out, or leaves curling are the sure signs of underwatered cactus. There are some special watering techniques to properly water your cactus.

How Do You Tell if A Cactus is Over Or Under Watered?

Signs of Underwatered CactusSigns of Overwatered Cactus
ShrivelingWilting
Yellow colorBlack or brown color
Spines and leaves drying, curlingMushy, soft stems and spines
Brittle rootsRotten roots

Basically – underwatered cacti are generally drier, whereas overwatered cacti are mushier. 

Important note:  sometimes the symptoms of overwatering and underwatering may be similar because the plant isn’t getting enough water from the roots in both scenarios. 

For example, wilting is more common for overwatering, but depending on the type of cactus, it can also happen when the plant is underwatered. The best way to know the difference for sure is to check the roots.

Signs of An Underwatered Cactus

Indoor potted cactus showing signs of underwatering

Cactus Turning Yellow

If the body of your cactus (or the leaves on your cactus) is yellow, you’re either overwatering or underwatering your plant. The leaves and the body turn yellow when they can’t produce chlorophyll as they regularly do, and this may be due to root damage. Your plant’s roots are either rotten, or they are experiencing drought. 

Cactus Shriveling

Your cactus will shrivel if it doesn’t get enough hydration simply because there’s not enough water in the tissues of your plant, which can result in distorted growth and shrinkage.

Cactus Wilting

This will happen typically when the cactus has a more thin and upright posture. It will slowly start to droop down and soften because there isn’t enough water in its tissues to keep holding it up.

Cactus Has Brown Tips, Brown and Dry Edges

If your cactus has meatier tissue, the edges and tips might start slowly wilting and dying because of insufficient water. This is manifested as dry, brown tips and edges. It could also be severe sunburn, which happens when you underwater your plant and leave it out in the sun.

Dry Brown Spots on Leaves

Dry brown patches on the leaves of your cactus might appear because it is too close to a heat source or direct sunlight, but they’re not hydrated enough to tolerate it. By underwatering your plant, you’re making it more susceptible to sunburn and heat damage. 

Cactus Leaves Curling

Your cactus’ leaves might curl if you’re underwatering them. Since they’re not getting enough hydration, they try to hold onto and retain as much water as possible, so that’s why their leaves might curl, in order to save resources. 

This can also be a sign of overwatering – the same thing might be happening because your plant’s roots are rotten and the leaves aren’t getting water from them.

Brittle Roots

Another way underwatering manifests is by brittle roots. If your cactus’ roots aren’t getting enough moisture and nutrients from the soil, they will become dry and brittle. They will also break off in pieces if you tug on them. 

Spines Falling Off

Because of insufficient hydration, the spines on your cactus will lose their strength and shine. They will become brittle and fragile and may start falling off if you touch them, or even on their own.

Identifying The Cause

Irregular Watering

Here are some tips for watering your cactus more efficiently:

  • When watering, it should be done less often but abundantly and thoroughly, so that all the soil in the pot is soaked. Watering a cactus often, but scarcely, can cause distorted growth because the soil is moist only to half of the pot and the lower part will always remain dry. 
  • Watering your cactus with cold water can shock it, especially in the summertime. Always water your cactus with room temperature water.
  • Water your plants with distilled water, filtered water or rainwater. Tap water contains chemicals that could harm your plant.
  • Make a watering schedule. Check the moisture of your plant regularly, especially in the summer when it might need more water than usual. 
  • In late March or early April, when your plant starts “waking up”, start gently misting it with warm water to make it used to the temperature. 
  • The first spring watering after the state of dormancy is good to do with warm rainwater(or warm distilled water), about 95- 113 °F  (35-45 °C), so you don’t shock your plant after its long sleep.

Fast Water Evaporation

Even though most cacti come from the desert, they won’t enjoy it if you leave them too close to a heater or in harsh direct sunlight for a long time. 

  • Keep your cacti in bright, indirect sunlight, and don’t put them too close to a heat source. This may cause water to evaporate more quickly from the soil, and as a result, cause your cactus to shrivel up and dehydrate. 
  • If you keep your cactus close to a radiator during winter, even though it’s in a state of dormancy, water it once a month so that it doesn’t shrivel up from the heat.

Soil Mixture Isn’t Suitable 

Good water drainage is a blessing for your cactus, but it must also be able to retain a certain amount of moisture as well as adequate nutrients. The soil needs to contain at least 30% perlite and sand (together) otherwise it will stay moist all the time and cause rotting in your cactus. So, according to this, this is the best and the most basic soil mixture which you can make at home:

  • Mix 40% normal potting soil, 20% perlite, 20% organic compost/humus, and 20% fine gravel or sand. 
  • The perlite and the gravel/sand create spaces between the soil molecules, leaving room for oxygen. This prevents the soil from being constantly moist which is very bad for a cactus, further preventing root rot. The organic compost gives cacti their needed nutrients.

Tips

  • Don’t add too much sand because the soil will become dry. 
  • Avoid peat-based mixtures because it has been proven that they attract mealybugs and other pests.

Wrong Size and Type of Container

  • Keep the cactus in a pot that is suitable for its size. Don’t keep small cacti in very large pots because they won’t properly absorb water. Don’t keep big cacti in pots too small for them, because there will be no space for their roots.
  • Be sure to buy a pot with drainage holes, otherwise, the excess water which doesn’t drain away might cause root rot.

Nitrogen Toxicity 

  • Too much nitrogen will encourage cacti to put on soft growth and be more susceptible to pests and diseases. Excessive nitrogen takes water away from your plants while leaving the salt behind. This dehydrates your plant while leaving its leaves brown, yellow, wilted, or curled.
  • To avoid this, don’t fertilize your cacti and succulents more than once a month during spring and summer, and don’t fertilize at all during the winter. Let the winter months be a period of rest for your cacti in order to avoid excess salt. 
  • For cacti, you can also use a granular fertilizer. It is durable, lasts for a long time, and also dissolves slowly which is good for cacti because they absorb food slower than other, regular annual greens. 

How to Revive an Underwatered Cactus?

 Saving an underwatered cactus is much more simple than saving a rotting one. Here’s what you need to do:

Cut off Severely Affected Parts 

  • Using a sharp, sterile knife, cut off the pieces/leaves of your cactus that are brown, dry, and completely ruined. These parts won’t recover and the plant doesn’t have any use of them.
  • Don’t cut off yellow parts – these aren’t rotten, they’re just dehydrated.     

Water the Cactus 

Most cacti will perk up simply after you water them. Water the cactus thoroughly and leave it to rest. If it doesn’t perk up in a few days, inspect the roots for any damage or investigate further to identify the cause of your plant’s stress.

Repot the Plant in Clean Soil 

Cacti should be repotted approximately every other year depending on the size of the plant. Older, bigger cacti don’t need to be repotted as much as younger and smaller ones.

If your cacti are dry even after watering them, the problem might be in the soil.

If you suspect that your cactus is drying out because your initial soil mixture isn’t right, if it’s too dry or your plant’s roots became too big for the pot, repot the cactus in a clean pot and use the soil mixture which I recommended earlier. 

Tip: Use a plastic pot. Plastic pots hold moisture better than any other material. 

Place the Pot in A Suitable Environment

Your cacti might be drying out because you put them in a spot with too much direct sunlight. 

  • Put the cactus pot in bright, indirect sunlight. Cacti can take some sunlight but too much direct sunlight will dry out your plant.
  • Cacti prefer temperatures between 60°F to 75°F (16 to 23°C), which is suitable for most homes.
  • Keep your cacti away from heaters and radiators. They can dry out your plant.
  • You can put your cacti outside during spring and summer but bring them back in once the temperatures start dropping( early Autumn.
  • Don’t keep young plants in direct sunlight, they will shrivel up more quickly. 

How to Water a Cactus

Watering from above and watering from below both have their benefits.  Both are totally valid ways to water your plant and it just depends on your choice. 

Watering from Above

  • Pour water directly onto the soil and avoid getting your cactus wet.
  • Don’t water the surface of the soil only – water your plant thoroughly until the water is coming out of the draining holes at the bottom. This way, you’re flushing out excess salt, reducing the risk of wilting and dehydration.
  • Don’t pour all the water at once! This can overflow your pot and the plant might not absorb all of the water the way that it should.
  • If you have a saucer under the pot, make sure to empty the water out of the saucer after a short time(maximum half an hour). Avoid leaving your plant sitting in water for too long, because it will absorb more than it needs and this could cause it to rot. 

Watering from Below

Watering from below is a very beneficial and efficient way to water your plant. 

By watering your plant from below, you are letting your plant absorb all the water it needs on its own, so the risk of underwatering or overwatering is reduced. 

The process is really simple. Here’s how to do it:

  • Start by filling up a large container with water (large enough to fit your pot in it). Of course, your pot should have drainage holes for the water to pass through.
  • The level of water shouldn’t be too high, just enough so that the pot is dipped in the water (approximately 2 inches).
  • Keep your plant in the container until you see that the top of the soil is moist. That means that the water has reached the top and your plant has absorbed all the water it needs. This should take about 10 minutes to half an hour depending on the size of your plant.
  • Once the top of the soil is moist, take your plant out of the container and put it in its original place. 

Important note : You should keep in mind that plants shouldn’t be watered exclusively from below.  

Watering your plants with only this method can cause accumulation of excess salt and dehydrate your plant in the process, because the water and all of the nutrients are being absorbed directly and the excess can not drain away. 

Occasionally water the plant from above so that the excess salt can be flushed out of the soil.

How Often Should I  Water My Cactus?

To answer this question, it’s important to know which phase your plant is in. 

During late autumn and winter, when it’s colder, you will need to water them less frequently and less thoroughly. Cacti enter a state of dormancy during winter and they won’t absorb as much water. Some cacti don’t even need water. 

The period of growth usually lasts from April to October. During this time, cacti should be regularly watered on a weekly basis and fertilized once a month.

In the period of full growth (late spring and summer), you should water plants in smaller pots every 5 to 7 days, while larger plants in larger pots should be watered 1-3 times a month. The amount of water and the time in between watering depends on heat and light. The greater the heat and light, the sooner the soil in the pot will dry out, so it should be watered more often and more abundantly. 

Here are some more tips:

  • Test the moisture of the soil before watering. Even if you have a regular schedule, your plant may absorb water faster or slower sometimes. 

You can do this in two ways: by using your finger or by using a moisture meter. 

‣ If your moisture meter is showing you that the soil isn’t almost or completely dry, skip watering until it is. 

‣ Stick your finger an inch into the soil. If the soil is moist underneath the surface, it’s not time to water your plant yet. 

  • Smaller and younger cacti need more water because they are in the process of growing.  Older cacti don’t need as much water. 
  • Let the soil completely dry out in between watering so that the roots don’t stay moist for a long time.
  • Know your cactus’ natural habitat. This way, you will know when its growing season is as well as its watering needs. This way you can find out if you should water your cactus during its state of dormancy. Some forest cacti, like the popular Christmas cactus, need a bit more water and humidity than desert cacti.

Final words

It is always safer to underwater your cacti than overwater them. These plants aren’t needy and will thrive under rough conditions, but they do need your love after all. All you really have to remember is that the general rule of thumb is to let the soil dry out in between watering and you’re good to go.

(Sources: University of Minnesota, University of Vermont)

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

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