If you’re new to growing cacti, figuring out their care can be a challenge. How often do you water a cactus? Can they really go without water for months like many people think? What’s the best way to water a cactus? How do you recognize an over- or underwatered specimen?
Let’s go into watering cacti and how to make sure yours grows big and strong! A happy and healthy cactus might even reward you with some beautiful flowers.
What affects how often to water a cactus?
Before we even attempt to go into talking about how often to water a cactus, it’s important to go over some general cactus care guidelines.
There are many factors that affect how often you should be watering your cactus. Without proper soil, potting and light, your plant won’t do well even if you’re perfect about watering.
- Soil. Cacti should be grown in very light, airy soil that allows water to drain in seconds. After all, their roots have not evolved to be able to deal with moisture for prolonged periods of time.
Normal potting soil is too dense for them and holds water for too long. Go for a 50/50 mix of potting soil and perlite instead, or even a no-soil cactus mixture.
- Planter. It’s no use going for a well-draining soil mixture if excess water just collects at the bottom of the pot. You should always use a planter with a drainage hole when growing cacti.
Terracotta planters are particularly popular, as they’re porous and allow water to evaporate through their walls.
- Light. Most cacti naturally grow in arid environments with little protection from taller trees. They’ve evolved to be able to withstand a good bit of sun and they won’t appreciate being grown in the darker corners of your home. Give your cactus a spot on the brightest windowsill you can offer! You can even grow it outside during the warm summer months.
All of the above has a big impact on the amount of water a cactus needs. If you grow yours outdoors in full sun, for example, it’ll need much more frequent waterings than the exact same species grown indoors on a windowsill.
The above is also why it’s impossible to give an exact answer to questions about how often a cactus should be watered. It all depends on the interplay between light and drainage, as well as other factors like temperature.
Figuring this out can be a bit of a challenge for beginning cactus enthusiasts, but you’ll find that after a while, you get a pretty good feel for when your plants need a drink.
Tip: You can find everything you need to know about planting cacti in the article on planting succulents indoors. Cacti are succulents too, after all.
How often to water a desert cactus
Most of the cacti we grow in our homes originate from arid, desert-like environments. You’ll naturally find them in the Americas: Mexico, the Southern US, Peru, Chile, Bolivia, Brazil and more. Some species even extend into Canada!
Most desert cacti can be recognized from the fact that they have a limited surface area. Take the orb-shaped Gymnocalycium (also pictured below), for example. Most of the plant’s volume is located on the inside, which helps combat water loss. They’re perfectly adapted to keeping as much water inside as possible.
So what does all this mean when it comes to how often to water a desert cactus? Well, you’ll have to keep in mind that they haven’t evolved to withstand wet environments at all. They love water, sure, but in between waterings, they like it dry. That leads us to the following watering guidelines for desert cacti:
- Follow the guidelines discussed in the first paragraph, using a very gritty soil mixture that allows water to drain right out of the planter. Provide lots of light, including direct sun.
- When it’s time to water, you’ll want to imitate a desert rainstorm: a big downpour. These plants are not used to receiving little bits of water here and there, they prefer being flooded periodically.
- Pour water into the planter until it comes running out of the drainage hole, thoroughly soaking the soil. Make sure the water can drain right out!
- Place the cactus back in its usual location and leave it there until the soil has dried completely. You may end up watering every few days (during summertime in full sun) or maybe just every other week (indoors on a sunny windowsill).
- If your cactus is looking a bit wrinklier than usual, you’ve probably waited too long. It should bounce back, but water a bit sooner next time! If the plant remains wrinkly, its roots might not be reaching the water properly.
There are sources out there that recommend watering cacti very rarely, such as giving a tablespoon every few months. This is not the way to go about growing these succulents at all: they do appreciate plenty of moisture. It’s just that they can’t be left in moist soil for extended periods of time.
Tip: Keep in mind that like other houseplants, cacti need less water during the winter months. Because there’s less light they won’t be actively growing, meaning they don’t use up as much moisture.
How often to water a jungle cactus
Let’s move on to a type of cactus that’s less commonly known outside of houseplant enthusiast circles. Not all cacti grow in (semi-)desert environments. Some can actually be found in tropical jungle settings, often growing on trees in an epiphytic manner.
Jungle cacti, like the popular Christmas cactus and Easter cactus, can generally be recognized by the fact that they haven’t evolved to limit their surface area like their desert cousins. Take the specimen in the photo below, for example: its leaves are almost as thin as that of a non-succulent plant.
Because jungle cacti grow in habitats that usually receive plenty of moisture, they won’t appreciate being treated the same way as desert cacti. Although they still need good drainage, it’s a good idea to use a soil mix that does retain a degree of moisture.
Letting the soil dry out entirely between waterings is usually not recommended, with many jungle cacti liking their medium ever so slightly moist. Some important watering guidelines for jungle cacti include:
- Use a soil mix that matches their epiphytic nature. They naturally grow on trees, so their roots don’t like to be compacted, and they need a mixture that drains excess water but also retains some moisture. Try mixing perlite, orchid bark, potting soil, coco coir and/or peat.
- Less light is needed for jungle cacti and they generally don’t appreciate full sun. However, they should definitely not be in the dark either. Without plenty of indirect light, the plant won’t be able to use up the water you give it and start rotting.
- You can water most jungle cacti when the top inch or so of their soil has dried out; stick your finger in the medium to test if you’re not sure.
As you can see, there is a pretty big difference in watering needs between jungle and desert cacti. Don’t make the mistake of treating one like the other. Identify the species you have and water it accordingly, or it might end up too wet or dry.
Tip: If your jungle cactus appears wrinkly, have a look at the soil. If it’s very dry, you’ve probably waited too long to water. If it’s damp, you may be watering too much and there is a chance that root rot has set in.
Overwatered cactus
For the cacti that don’t make it, overwatering is probably the leading cause of death. Not just do houseplant enthusiasts sometimes tend to love their cacti to death, but cacti also tend to be placed in locations that are too dark or planters that lack drainage. A fatal combination!
So how do you know if you’ve overwatered a cactus?
- In the beginning stages, an overwatered cactus may appear wrinkly even after watering. This is because root rot has set in, meaning the roots can’t properly take up water any more.
- If the problem is not dealt with, you might start seeing black coloration appear at the base of the stem. This means the rot has progressed from the roots to the actual plant itself.
- An untreated plant can end up rotting completely, sometimes from the inside out. The whole thing becomes squishy, black, and just all-around pretty gross with a nasty smell.
Obviously, if your cactus is in the last stage of rot, there really isn’t anything you can do anymore. However, if you’re just dealing with root rot or light stem rot, there might be hope.
If you see any signs of rot, it’s time to take action fast. Take the cactus out of its container and discard the soil. Cut away any parts that show even slight signs of rot. In cases of stem rot, the guide on how to propagate a cactus will help you with this part!
Once the surgery is finished, prepare a suitable planter. Use a fresh soil mix that’s suitable for the type of cactus you’re dealing with. Pot up the plant and make sure it gets a good amount of light. Water according to the guidelines described in the previous paragraphs and with some luck, the rot won’t return.
Did you know? Stem rot on cacti can be confused with woody stems. When certain cactus species age, they might form a hard, brown layer on the bottom of the stem. If the layer is hard rather than squishy, it’s not rot; your cactus is just maturing and corking.
Underwatered cactus
If you forget to water your cactus for a bit, it can start to look pretty sad. Underwatered cacti will wrinkle, shrink and even turn yellow-brown if left for too long.
As alarming as their appearance might be, most cacti can be brought back to life with a good soak. Just don’t leave them for too long, as they do have a point of no return! You’ll also have to start paying more attention to the plant in the future, as repeated underwatering can eventually simply become too much.
Cactus and watering can photo: © mallmo on Adobe Stock.
