Cacti Plant Care Guide

How often to water a cactus? What is the best potting mix for cacti grown indoors? How to propagate a cactus? How much light do indoor cacti need?

These questions related to how to care for cacti indoors are probably on your mind if a little green, spiky friend has recently joined your plant family. No worries! Caring for cacti as houseplants is really easy.

In this detailed cactus care guide, you will find important tips and tricks on how to care for these drought-tolerant plants.

To understand how to care for desert cacti indoors, it’s important to know where they come from and what environment are these plants used to. So, where do cacti originate from? Most cacti originate from the deserts of North and South America. As you can probably imagine this means that they are used to sunshine all day long and little to no water. Cacti are pretty tough as they have acclimatized to grow in such a harsh environment and have adapted to survive in places where no other plant or soul would ever make it. This is just to give you a basic idea of how badass cacti are!

Growing in the desert, cacti are thus, used to harsh bright light, and dry climates and are extremely drought-tolerant. They have adapted to survive in such conditions by storing a lot of water in their stems. Cacti not having any actual leaves is part of their adaptation strategy to the harsh climate. Did you know that actually, cacti don’t have real leaves? What we imagine when we hear the word “cactus” is actually a succulent-like stem with branches spines and scales. Cacti don’t have any true leaves but the spines are modified bud scales, i.e. leaves.

Cactus comes from the Latin word “cardoon” and there are a lot of different varieties found in nature. So how many different cacti are out there? Quite a lot. In nature, about 300 genera and 3 000 different cacti species have been documented so far. If you are a cacti lover and a collector, you don’t need to worry though. All different cacti have pretty much the same care needs.

Cacti are beginner-friendly plants that can be grown both indoors and outdoors but this care guide will focus on caring for cacti as houseplants. As mentioned, cacti are really low-maintenance plants but they do need some TLC to stay healthy and happy. Namely, keep them warm, keep them bright, don’t drown them, and don’t touch them much because… ouch, they can be prickly!  This detailed cactus care guide includes tips and tricks on how to keep your cactus (or cacti) thriving so you can enjoy your little slice of the desert at home for long years to come.

This post may contain affiliate links. Read our Privacy Policy and Disclosure here.

Continue reading for a detailed guide on how to care for a cactus grown indoors.

1. How much light does a cactus need?

Cacti are one of the most popular houseplants due to their low-maintenance care requirements, but how much light do cacti need? Different cacti species have different light requirements. Some will happily grow in direct sun (outdoor cactus types) while others will do fine also in a medium-light location. But to suit them all, the golden middle is bright, indirect light for at least 6 hours daily.

Cacti, as desert plants, are adapted to long periods of direct sunlight, so they need bright light to thrive indoors. However, bear in mind something important: While they are adapted to survive in hot, sunny climates, cacti can actually burn if they are exposed to too much light, especially when they are still young and not properly acclimatized to the harsh rays of sunlight. Therefore, if your cactus is getting scorched by the sun, it is best to place it in a bright spot that receives indirect sunlight. Sunburn marks on your cactus will look like parts on the stem that have a yellow-tinted discoloration and a dry appearance to it. If you notice scorched marks, the light is too strong for your cactus. Move the plant a bit away from the window or use a window film or translucent curtain to filter the light.

Tip: If you want to grow a cactus outdoors, it is always advisable to gradually introduce it to more direct exposure to light by increasing steadily the number of direct light hours the plant is receiving.

Cacti will grow best in a south- or west-facing window, where they will receive several hours of natural light each day. If you don’t have a bright spot for your cactus, you can supplement it with artificial full-spectrum grow lights.

Signs that your cactus is not receiving enough light:

There are a few signs that a cactus is not receiving enough light. The cactus may start to stretch, or grow taller and thinner. The stem may become lighter in color. The cactus may also stop growing altogether or grow considerably slower, and usually, cacti that aren’t receiving an adequate light will not bloom.

Although your cactus might survive in a location that is receiving medium light, it will not thrive there. Cacti, in general, won’t tolerate a low-light location. They can survive for short periods in a low-light location but will for sure not thrive there and there is a high risk of rot issues developing due to overwatering.

How much light (PAR) does a cactus need? The PAR number varies for different cacti species but a good general rule is that for optimal growth, provide your cactus with a light source of PPFD of at least 500umol/m2/s and aim for a lighting period of 12 to 14 hours daily.

What is the cacti light requirement in lux? Again the lux number varies.At least 3, 000 lux (300 foot-candles) are needed to ensure the survival of most cacti. For optimal and steady growth, most cacti need at least 15, 000 lux ( 1, 500 foot candles) to 20, 000 lux (2, 000 foot candles).

You can use a light meter (lux meter) to measure the lux (food candles) number or the PAR (PPFD). If you don’t have a light meter on hand, there are phone apps available.

Alright, so a cactus needs direct to indirect bright light? But what does this mean? If these terms sound confusing to you (like they did to me at first too!), make sure to read our Light Guide for Plants.

2. How Often to Water a Cactus?

This is a difficult question to answer as it depends on many factors such as the type of cactus, the size of the pot, the type of potting mix, the temperature, the amount of light, etc. There is not a one-size-fits-all answer regarding how often to water a cactus and even at your home, different cacti will require to be watered more or less frequently.

Watering cacti is one of the most important plant care factors that you need to nail to ensure the survival of your cactus. Keep the following in mind: less is more when it comes to watering your cactus.

Remember how I said that desert cacti are used to harsh and dry climates? You want to mimic this at your home too. Desert cacti store a lot of water in their stems, thus, overwatering can cause them to suffer fast and it can lead to a number of problems including root and stem rot, fungal infections, and wilting.

Important: Not all cacti are desert cacti! There are cacti that are native to tropical rainforests (the Christmas Cactus or the Jungle Cacti, for example) and need to be watered more frequently, although they would also tolerate periods of dryness.

Should you water your cactus on a fixed schedule? No. Some cacti would need to be watered every week while others every 2 weeks during the growing season. While during the dormant season (October to March), some cacti wouldn’t need to be watered for a whole month or more.

You should aim to check the soil or growing media of your cactus each and every time before you water it. In other words, you should always let the soil of your cactus dry out completely before watering it again.

Before you water your cactus, check the moisture in its soil/substrate. For this, a moisture meter might come in handy and you should water your cactus when the meter shows “low” or “dry”. Usually, the level of moisture can also be checked by feeling it with your index finger, but for cacti, you would need to go all the way to the bottom and ensure it’s dry. So the finger test might not work very well for cacti. Instead, lift up your plant’s pot. Does it feel completely light? Check also the bottom part of the pot, i.e. where the drainage holes are – does the soil look dry? If the pot of your cactus feels very light, it is time to water it.

How to water a cactus:

Whenever you are watering your cactus, ensure that you are fully saturating the soil/substrate. To irrigate your cactus properly, water the plant until water starts coming out of the bottom of the pot, i.e. the drainage holes, and then stop.

Tip: To conduct this test, make a mental note beforehand of how heavy the pot feels when you just watered your cactus.

Signs that a cactus is overwatered include: the stem is soft and mushy, there are brown or discolored, soft patches on the stem, the cactus is wilting and leaning over, stunned growth, there is white growth on top of the soil of the cactus, there is an unpleasant moldy smell coming from the pot. And an invisible sign: root rot. In most cases, an overwatered cactus might be able to bounce back on its own. To help a cactus recover from being overwatered, just skip watering it until the soil has completely dried out. Also, place the cactus in a spot where it is receiving bright light and where there is enough air circulation. A small fan can help with that. After the growing media has dried out completely, you can water it again and observe whether the situation is getting better. IF your cactus is not able to recover from being overwatered, the issue might be more problematic and there might either be stem or most likely, root rot going on. If you suspect that your cactus has root rot (or stem rot), you need to act fast to help the plant survive. In these cases, the treatment is a bit more complicated than simply letting the potting media dry out. For these situations, we have a step-by-step guide on how to save plants from root and stem rot.

As mentioned, underwatering issues are really rare when it comes to cacti but of course, can sometimes occur. Signs that your cactus is underwatered are: the cactus might start looking shriveled and wrinkled. The plant might stop growing or produce any flowers. If you have accidentally forgotten to water your cactus for quite a while (this can happen to all of us!) just simply give the plant a good drink. Bottom watering your cactus in case it is underwatered can speed up the recovery process. While the plant bounces back from receiving too little water, make sure to shield it from any direct exposure to harsh sunlight as this might put unnecessary stress on an already stressed cactus.

For optimal health, longevity, and growth, it’s important that you water your cactus less frequently but fully. Since cacti require to be watered less frequently than other houseplants, and if you are using a potting mix without sufficient drainage, the soil might become hydrophobic and compact. Read our Houseplants Watering Guide on best watering tips for your cactus.

3. What is the Best Potting Mix for a Cactus?

There are different growing media that can be used to successfully grow a cactus indoors. You can opt to plant your cactus in a potting soil mix, mineral substrate, in semi-hydro and some cacti can even be grown hydroponically, i.e. in water alone.

If you are used to growing houseplants in potting soil, then, perhaps this would also be a good option for your cactus. The best soil-based growing medium for a cactus is one that is well-drained and has a high sand content. Cacti do not like to have their roots wet for long periods of time, so sandy soil that drains quickly is ideal. A cactus that is grown in a pot will need a potting mix that is specifically designed for cacti and other succulents. This type of mix will have a high sand content and will drain quickly. However, bear in mind that it’s not advisable to grow your cactus in sand alone, as it might become compact fast.

Also, don’t use just any general potting mix for your cactus as the general-purpose potting soil sold at most stores is not suited for cacti as they retain too much moisture and don’t provide enough aeration.

If you feel like going the extra mile for your cactus, then you might want to ensure that you know exactly what is in its potting soil.

Here is a simple (but effective) DIY recipe for potting soil for a cactus that you can mix at home: equal parts coarse sand (fine sand won’t provide enough aeration), perlite, and good quality potting soil. Mix the ingredients listed plus a bit of love and your cactus will surely love it. 😊

And don’t forget: always aim to plant your cactus in a pot that has a drainage hole. You don’t want a root rot situation and the water needs to be able to flow freely out after each watering so that salts are not getting built up in the soil. If you are wondering what would be the perfect pot for your cactus to grow in, the answer is a terracotta pot. Unglazed clay pots provide much better aeration compared to common plastic ones. If you opt to plant your cactus in a terracotta pot, there is also less risk of the plant being overwatered because… you guessed it! Terracotta pots breathe. Also, plastic pots are bad for the environment so opt for alternatives whenever possible.

On the other hand, you don’t need to grow your cactus in organic media and can opt to grow it in a soilless growing media. We have a special substrate for cacti and succulents that is well suited to meet the needs of these plants. The substrate in our shop stores moisture and nutrients and provides them to plants just when they need them, while at the same time ensuring a high level of aeration around the roots.

Can you grow a cactus hydroponically? Yes, especially if you are rooting one in water then you can freely continue growing it in hydro. You can also opt to grow your cactus in semi-hydro. As these plants have thin and mostly shallow roots, LECA is not ideal for them as the balls are too big. Pon and substrate for cacti and succulents, on the other hand, can be used for a cactus.

4. How Much Humidity Does a Cactus Need?

If you have tropical plants at home that require higher humidity levels to thrive, you might be wondering: do I need a humidifier for my cacti?

Remember how I mentioned that cacti are desert plants? This is very important to keep in mind when answering the question: how much humidity do cacti need.

When it comes to cacti and humidity, less is more. Most cacti feel and grow at their best when the relative humidity around them is low. Thus, normal room humidity is fine for these desert plants.

So what is the optimal humidity level for a cactus indoors? As a general rule of thumb, it is recommended that cacti be kept in an area with low humidity (between 20% and 40%) in order to prevent them from rotting. Of course, the humidity level number can vary between different cacti species but is a good starting point.

You can measure the humidity level by using a hygrometer. If a cactus experiences high humidity levels (60%+) for a long time, the plant might start rotting. If you notice that your cactus is not consuming its water as fast as it should or if there are signs of stem and root rot, then make sure to check the humidity around your plant as these all are signs of a cactus experiencing too much humidity. In such cases, using a dehumidifier or increasing the airflow around the plant, by using a small desk fan, for example, might help.

Important: Cacti don’t like their stem getting wet so avoid misting or splashing water directly on them.

Hint: If you are propagating a cactus, however, raising the humidity levels might be helpful. Just always ensure that there is a flow of fresh air around to avoid rot-related issues.

5. How Often to Fertilize a Cactus and Which Fertilizer is Best? 

Most cacti are native to desert regions and thus used to infrequent watering. Many cacti only receive rainwater a few times per year. As a result, compared to other houseplants, cacti need to be fertilized less often. Light fertilization (about one-quarter to one-half the recommended strength for most plants) monthly during the growing period is usually sufficient. However, if you notice that your cactus is not growing as vigorously as it should be, you may need to fertilize it more frequently.

During the winter period from October to March, your cactus will most likely slow down its growth rate significantly or not grow at all. This is also known as the dormant period. During this period, you don’t need to fertilize your cactus at all.

What type of fertilizer is best for a cactus?
Cacti are best suited for a fertilizer with low nitrogen content. This is because too much nitrogen can lead to the cactus becoming “leggy”. High phosphorus content is also beneficial, as it encourages strong root growth. So choose a fertilizer that has higher phosphorus to nitrogen content. There are a lot of specially formulated fertilizers for cacti and succulents that will work well for just about any cactus. You can use either a slow-release fertilizer or opt for a liquid one (which you would need to apply more often) for your cactus.

How often to fertilize a cactus indoors?
Depending on what your cactus is planted in, i.e. potting soil or hydro, your cactus would need to be fertilized differently.

If your cactus is growing in potting mix, you can use slow-release balls and apply them on top of the soil 2 times per year, once in March and once in July. Or as indicated on the packaging. Alternatively, you can also use a liquid fertilizer for your soil-growing cactus and never go over the recommended dose by the manufacturer. As mentioned, most cacti grown in soil need to be fertilized monthly with a diluted fertilizer dose. Don’t fertilize your cactus during the dormant period.

Tip: If your cactus is young, always start with a highly diluted fertilizer dose, something low like 10 to 15% of the recommended amount. Observe how the plant handles the fertilizer before increasing the dose gradually.

If your cactus is growing in a soilless substrate or hydro, use a fertilizer that has been specially formulated to be used with hydro. Regular fertilizers might burn the roots due to possibly high content of salts. For cacti grown in hydro or similar growing media that contain no natural nutrients, follow the instructions on the fertilizer label. Usually, cacti grown in soilless media need to be fertilized every second watering.

Whenever you are watering and fertilizing your cactus, adjust the pH of the water to around 5.5 after you have added fertilizer. Cacti tolerate a pH level between 4 and 6.5 but keeping the pH to as close as 5.5 as possible means that your cactus will be able to absorb nutrients at its best.

Use a pH meter to check the pH value. If the pH is too high, you can use acid (eg: citric acid) to bring it down. If it’s too low – use a base (eg: calcium carbonate or baking soda) to bring it up.

6. Do You Need to Clean a Cactus?

Cacti remain pretty dust-free in most cases so they don’t need a regular cleaning routine like, Monstera does, for example. However, if you notice that your cactus is breaking this unwritten rule then it’s time for a little refreshing session for the little spikey boy.

How to clean cacti from dust?
If you need to clean your cactus from dust and other dirt, don’t use water and don’t shower it, remember? Cacti hate being wet. Instead, use a soft brush (a makeup brush, for example) and brush off gently the stem of your cactus. Keeping your cactus clean helps the plant photosynthesize more efficiently and prevents pests from hiding in the dust.

7. The Best Growing Temps for a Cactus

The ideal temperature range for cacti growth depends on the specific species. Some cacti, such as the Christmas cactus, thrive in cooler temperatures around 15°C to 21°C ( 60°F -70° F ). Others, such as the saguaro cactus, need warmer temperatures around 26°C to 30°C ( 80°F -85° F ).

Cacti typically prefer warm temperatures and lots of sunlight. They are desert plants, after all, well, at least desert cacti are, rainforest cacti are another story.

Some cacti can tolerate colder weather, but they will not grow as vigorously. Cacti that are specially labeled as frost-resistant can even survive temperatures even below 10 °C (50 °F). But bear in mind, that the majority of cacti will start suffering from cold damage if the temperatures are below these lows.

Therefore, for optimum growth, try to keep the temperature around your cactus between 18°C and 28 °C (65 °F to 85 °F).

8. Rotate Indoor Cacti Regularly

A cactus will always try to some extent to grow towards its main light source. Some of them, like the Pitaya Cactus, will even go to seemingly impossible lengths to get as much light as they need. Therefore, rotate regularly your cactus so that it can grow equally on all sides. Using a grow light and positioning it just above the cactus can help with that as well.

9. How to Identify and Treat Pests on Cacti

Cacti seem to not be the first choice on the menu for any pests so for the majority of the time, especially if you grow your cactus indoors, it will most likely remain pest-free.

However, there are also exceptions. The most common pests that attack cacti indoors are mealybugs, also known as soft-shell scales. Mealybugs are very easy to spot. They are about 2-4mm long, oval-shaped, and look like white, fluffy turtles crawling on your plant. Spider mites and thrips are usually not found on cacti unless some of them got lost or had no other option on their menu.Outdoors, cacti can also become the target of aphids.

Pests infestation is once again rare on cacti but a pest problem can cause stunted growth, deformed parts, and loss of vigor.

Every plant parent will tell you this: make it part of your routine to regularly inspect your cactus (and all plants) for pests. The general rule is to do it each time you water a plant but once per month should also suffice. When caught early, pest problems on plants are very manageable. A real pest infestation is a horror to get controlled.

If your cactus has suddenly become the target of pests, make sure to check our step-by-step guide on how to get rid of pests on houseplants.

How to treat a pest problem on a cactus: if you spot pests on your cactus, the first step is to isolate the plant. Next on, give it a good shower but try not to soak up the soil with too much water. After your cactus has dried out, apply an organic pesticide (eg: neem oil, garlic solution, soap). Repeat as necessary. Use chemical pesticides only as a last resort as they are harmful to beneficial insects and the environment.

10. How to Propagate a Cactus

Cacti are easy to propagate. Young plants, however, take their time and in some cases, are considered mature plants after 6 months have passed.

There are 3 ways to propagate a cactus: from seeds, offsets, or cuttings. Seed propagation of cacti is rare as not every cactus blooms eagerly indoors and some need years to reach maturity before they can flower. 

How to propagate a cactus from seeds: 

If you are lucky enough to get your cactus to flower, you might be in luck and might be able to collect some seeds. This is because a lot of cacti are self-pollinating. This means that they are able to produce viable seeds without any external assistance. Some cacti, on the other hand, might need your help to transfer fresh pollen from the anthers to the stigma. 

If the pollination of your cactus was successful, soon enough you can collect some seeds from it. Once you have seeds, they can be sown in spring or summer. Spread the cactus seed on top of sterile potting soil (or substrate) for cacti and succulents and lightly cover the seeds with sand or grit. Spray generously with water. Keep the seeds moist and warm. A propagator or a heating mat might come in handy. 

How long do cactus seeds take to germinate? This depends highly. Some cacti seeds germinate after 3 weeks, while others need months. After your seeds germinate, you can position the little cactus seedlings in a location that receives bright indirect light. Use a grow light if you don’t have a natural light source available. 

To propagate a cactus through offsets (offshoots) or cuttings, there is an important thing to keep in mind: propagate your cactus only during the growing season. Cacti become semi- or fully dormant during the winter months, hence, the chances of successful propagation are highest during their active growing phase. Thus, the best time to propagate your cactus is during spring or summer.

Does your cactus have offsets, i.e. offshoots? Then it can be propagated from them. For more information on offsets propagation, check this guide out: How to propagate plants from offsets. But to summarize: the technique is pretty simple. Offsets can be removed from the parent cactus plant in spring or summer and replanted. 

Propagating a cactus from stem cuttings

The most common way to propagate a cactus is through cuttings. You probably are already familiar with general plant propagation methods, if not, check our article on the different ways that plants can be propagated. And most likely already have experience with taking cuttings from a plant, sticking it in water until it forms roots, and then planting it.

So you might be wondering now? But I don’t see any leaves on my cacti, how do I take cuttings from a cactus to propagate? No worries, I got you and I will explain now.

Here is how to propagate a cactus from cuttings: 

If you want to propagate a cactus, using a sharp knife that has been disinfected (eg: 70% rubbing alcohol), cut away the upper part of the cactus. Yes, that’s right. Chop off the head of your cactus. Ideally, this part will be at least 4cm to 8 cm (1.5 to 3 inches) long.  

Allow for the wound to callus for about 24 hours. After this time has passed, you can place the cactus cutting in a sterile potting mix or in an inorganic substrate for cacti and succulents. Spray the top of the soil/substrate but don’t get it too soggy. Place the little darling in a bright and warm location and mist the soil from time to time. Soon enough, your little cactus cutting should start developing roots from the place where it was cut.

Psst, did you know that you can propagate a cactus in water? Yup, that’s right! Simply place the cutting in clean water (rainwater or distilled would be best) and ensure the water level covers the bottom quarter of the cutting. Change the water regularly with a fresh one and wash off any slimy stuff that might form on the cactus cutting. Wrapping the cup or glass where the cutting is all around with alluminium foil (including the opening of the cup), prevents any extra bacteria from getting in and can also speed up the rooting process as usually, roots form faster when they are in the dark. Once the cuttings have formed roots, you can either wait until they are large enough and transfer the little cactus into soil or substrate for cacti and succulents. Alternatively, you can continually grow it purely in water or in semi-hydro. 

How long do cactus cuttings need to root? Most cactus cuttings will take about four to eight weeks to root. 

How to care for a cactus cutting to ensure it roots:

Place your cactus cutting in a location where it is warm and receives bright, indirect light. If you want to speed up the process for your cactus cutting rooting, you can use a grow light if there is no natural light source available. Propagation mats are also useful if the temperatures in the room where the cutting is are below 23 °C (73.4 °F). Raising the humidity to about 60% might also speed up the rooting process. Consider a humidifier, a propagation, a humidity dome or simply use a zip-lock bag. Make sure to open the bag daily to ensure enough circulation of fresh air.

We have a step-by-step guide on how to propagate houseplants from cuttings so make sure to check it out as it explains how to avoid common mistakes when it comes to plant propagation.

11. How to Repot a Cactus

How often to repot a cactus? The time a cactus would need to outgrow its current pot varies based on different species. Some cacti need to be transplanted every 2 to 3 years, while others can happily live in their pot for 10 years. Some cacti will show signs of needing to be replanted, such as stunted growth or fewer blooms, while others may not.

Before you decide on repotting a cactus, make sure that the plant will benefit from it as repotting any plant causes them stress. Check out our guide on Repotting Done Right to make sure that your cactus needs to be replanted for its own benefit.

Unless you are dealing with a cactus problem, like stem or root rot, wait with repotting a cactus until the growing season, i.e. from March to October. This is because cacti go completely or semi-dormant during the winter months and repotting them then might stress the plants more than necessary.

Psst, did a new cactus just join your plant family by arriving in the mail? If your cactus has just arrived, allow it to rest and recover for 2 good weeks before repotting it.

So have you decided that you are definitely repotting your cactus? Let’s get right on it then!

How to repot a cactus – prepare beforehand:

Let’s get one thing out of the way. Does your cactus have needles? Get gloves. Seriously. Before you even think about repotting a cactus, arm yourself with bullet… er, thorn-proof gloves. Most cacti have very sharp and very mean needless that might stick into your skin with ease and create an allergic reaction. Don’t risk it, get gloves. Alternatively, you can use grill tongs! Ha. Silicone Tongs are soft enough to not injure a cactus, yet, they can hold the plant firmly too. So if you don’t have thorn-proof garden gloves, use silicone tongs to repot a cactus.

Naturally… If your cactus is still a baby or it doesn’t have needles, no need for the extra security equipment.

Next on, choose the next size pot for your cactus. Don’t go 10 sizes bigger when choosing the new pot for your cactus as it might not keep up with the extra moisture in the soil and… you guessed it, rot might occur. Would be also great if you choose a terracotta pot for your cactus for the extra breathing abilities of this material. Also, prepare fresh growing media for your cactus. You can choose to use either a potting mix for cacti and succulents or a mineral substrate.

Got everything on hand to repot your cactus? Time to get down to business.

Hint: It’s much easier to get a cactus out of its pot when the potting mix is dry.

How to repot a cactus – the procedure:

Put on your gloves or grab the silicon tongs and gently pull out the cactus from its current pot. It should come out fairly easily if the media inside is dry. If the pot is plastic, you can gently squeeze it while pulling the cactus up to free it. IF the pot is terracotta, use something, like a pen, to push the plant up. To do this: insert the pen into the bottom hole of the plant (you know, the drainage hole), and gently push while still holding the cactus and pulling it up. Once your needle-boy is out, it’s time to pot up the cactus in its new pot.

Don’t try to separate old potting media (unless there is some issue like rot or smells funky) from the roots as cacti have a really gentle root system.
Plant the cactus by feeling approximately one-third of the pot with the growing media, then positioning the cactus in the middle and adding additional soil or substrate. Water the cactus thoroughly after repotting it. Place it in a warm location that receives bright, indirect light.

13. Cactus Care: Common Issues with Cacti

Due to their natural origin, the desert, cacti are pretty tough and are resilient to almost anything. However, there is one thing that can bring a cactus down – water. Overwatering a cactus is perhaps the number one reason for these, otherwise really hardy plants, to become sick.

Stem and root rot issues are a common occurrence with cacti precisely because of improper watering routine. If a cactus doesn’t receive enough light, isn’t planted in a potting mix with enough drainage, and doesn’t have enough airflow around it, the plant can’t drink as well as it should. As a result, water doesn’t vaporize fast enough from the soil and rot settles in.

How to save a cactus that has been overwatered? Often, if you have overwatered a cactus, the plant might be able to bounce back on its own. In these cases, provide the cactus with light (grow lights can help) and airflow (a small desk fan, for example), and if needed – decrease the humidity (use a dehumidifier if needed). These simple steps will aid the drying process of the soil. Wait until the soil has completely dried out before watering the cactus again and observe how the plant feels in the following weeks. If your cactus doesn’t have a serious rot-related issue going on, it should go back to its perky (and pokey!) self soon. If your cactus starts looking worse instead of better, however, there is a good chance that it suffers from either stem or root rot. In this case, head over to our detailed guide on how to save plants from rot.

Fungal and bacterial diseases are not really common on cacti as these plants tend to grow in less-humid environments. However, sometimes, especially if a cactus is grown outdoors, fungal diseases might appear.

Signs of fungus on a cactus: Fungal spots will show up on your cactus either as an extra growth or as tissue wounds. The most common fungus on cacti is powdery mildew.

Powdery mildew looks like off-white-colored spots on your cactus. You can wipe them off but they will appear again. Powdery mildew favors cold, wet, and dark conditions. It is one of the most common types of fungal diseases on plants outdoors in winter and early summer when there is a lot of rainfall, humidity, and lack of sufficient light and airflow. Just like with any other fungi, if you remove its favorable conditions, it will stop from growing on your cactus.

Rust fungus, also called rust disease, is another common type of fungal problem on cacti. Rust fungus looks like orange to rusty-colored patches on the stem of the cactus. The spots might look like extra growth on the plant at first but later can develop into brown and dry parts of missing flesh.

How to get rid of fungus on cacti:

If you suspect that your cactus has a fungal disease, isolate it immediately from the rest of your plants. Next on, access how much the fungus has spread. Is it at the top of the cactus? The sides? Is it covering the complete plant? In certain cases, i.e. if the fungus is only on the top part of the plant, the best would be to cut this part away as any injured tissue will not recover. On the other hand, Ii the fungus has taken over the bottom part of your cactus, consider cutting the upper healthy part and propagating it. If the fungus has spread all over your cactus and there is no option of cutting it off without damaging too much the plant, then leave it be.

Spray the whole cactus with an appropriate fungicide. A copper-based fungicide or sulfur powder will work well for most types of fungi. Repeat as necessary and observe the plant closely. Provide it with bright, indirect light, good airflow, and hold back a bit on watering it. If your cactus is not getting better after multiple fungicide applications and correcting environmental triggers, then consider disposing of it for the sake of your other plants.

How to prevent fungal diseases on a cactus: As with most plant-related problems, prevention is easier than treating a disease. Of course, there is no golden recipe for 100% prevention of fungal issues but the following are the guidelines to keep in mind to keep your cactus healthy and fungus-free.

To prevent fungus diseases (like rust or powdery mildew) on a cactus: Ensure that the environment around your cactus is not fungus-friendly. I.e. don’t mist your cactus, don’t keep the plant in high humidity, and ensure adequate airflow and sufficient light. Hold back on watering until you are sure that the potting soil has had adequate time to dry out. Use a pot with a hole and a substrate with good drainage.

Edema on a cactus:

What is edema? Edema, also called oedema, are physiologically-related imperfections that sometimes can be seen in plants. Edema spots are not a virus, a fungus, or any other form of a disease. Edema spots are usually harmless to a cactus, are not infectious to other plants, and are just a physical imperfection, indicating that there is some problem with transpiration. What is transpiration? Similar to a human’s blood circulation, transpiration in plants is the movement of water throughout the different parts of a plant. At some point, water needs to exit the plant through evaporation. However, when the cells have taken too much moisture than they can get rid of, they rupture.

How does edema look on a cactus? Edema, or oedema, spots look like dots on the stem of a cactus that are rather dark brown, a bit elevated (like a blister), and look moist. These spots occur on a cactus when the plant is not able to get rid of excess moisture. In other words, somewhere along the whole process of transpiration (i.e. at the point of evaporation), the roots of your cactus have taken up more moisture than the plant needs and can transpire. As a result, the cells on your cactus have taken up more than they can process. The build-up of moisture causes excess pressure and the cells bursts and die. You can’t really cure edema spots on a cactus but you can prevent even more from appearing.

To prevent edema spots on a cactus ensure that your plant is planted in a growing media with excellent drainage. Soil that is too compact around the plant’s roots is not suitable for a cactus and apart from rotting issues, can lead to edema. Also, ensure that your cactus is receiving enough light and that there is good airflow around it. Always allow sufficient time for the soil of your cactus to dry out between watering.

You see now that apart from pests, most issues on a cactus are caused by water. To keep your cactus happy, healthy, and thriving always ensure that its roots have enough oxygen, don’t water it too soon, and provide it with sufficient light. Don’t mist your cactus in any case and try to not splash any water on the stem while watering it. Bottom-watering your cactus might help you achieve that. Check out our detailed guide on how to water houseplants for tips on when is best to bottom-water a cactus.

14. Can You Grow Cacti in a Terrarium?

Yes, you can grow a cactus in a terrarium. Cacti are well suited to growing in containers and terrariums as they are slow-growing. They are drought tolerant and do not need much water, making them ideal plants for growing in a closed environment.

Just a word of caution: generally cacti prefer an environment that resembles the condition of a desert. One placed in a terrarium will be exposed to higher levels of humidity, thus, ensure that you are providing your terrarium-grown cactus sufficient light and are not watering it too often. Also, use an open terrarium for your cactus, i.e. one without a lid.

We have specially tailored terrarium substrate mixes for cacti. Make sure to check in our shop for the DIY Terrarium Cacti & Succulents Set.

And hey, do you have everything prepared to build a little desert paradise for your cactus in a glass? Head over to our step-by-step guide on How to Make a Plant Terrarium to get started then!

15. Are Cacti Toxic?

Even though they have sharp needles (most of them at least, Jungle Cactus, I don’t mean you), cacti are not toxic to humans and animals. Eating them can cause some stomach discomfort, however, so it is best to be avoided. An allergic reaction can develop if a cactus needle pierces the skin for some people, so they are also best left alone and untouched.

Cactus Care: Final Thoughts

In this detailed plant care guide, different factors of caring for a cactus indoors were covered. Cacti are great beginner plants for beginners due to them being really easy to care for, and pretty much resistant to most pests and diseases.

Even though cacti are low-maintenance plants, they still need some care and attention so that they can thrive indoors. The following tips will help you care for your cactus and keep it looking at its best: place your cactus in a bright location, let the soil of your cactus dry out between waterings, and feed your cactus at least bimonthly during the growing season and enjoy all of its needly-glory. When the time is right, you can easily propagate your cactus from seeds or cuttings.

If you decide to grow your cactus in a bit not so common way, then go ahead and give terrarium gardening a go. Cacti are well-suited to be grown in a terrarium!
We hope that the information in this cactus care guide will make your cactus-growing journey even more enjoyable and that your little (or big!) poke-y friend will keep you company for years to come. Happy growing! 😊