A cactus is a hardy plant that does well without a lot of attention. However, repotting your cactus every now and then is an essential part of making sure your beloved plant stays as healthy as possible. So how can you tell when it’s time to repot your cactus?
You should repot your cactus if its roots are growing through the drainage holes, which signifies that your plant is root-bound and has outgrown the container. A withered or top-heavy cactus is also a sign that you should repot it soon. Typically, you should repot a cactus every 2-4 years.
The rest of this article will elaborate on when you should repot your cactus and the best ways to do so. Let’s get started.
Cactus Growth and Potting Needs
Cactaceae is a large and diverse family of plants with modified stems and leaves well-adapted to arid conditions. Most members of this family are slow-growing, especially those commonly selected as houseplants.
These indoor cacti species typically have a dense network of fibrous roots that grow shallowly in the soil. Because of this, they generally prefer to be snug in pots only about an inch (2.5 cm) wider than their diameter.
When grown in snug conditions indoors, compact cacti species grow about 1/2 to 1 inch (1.25-2.5 cm) annually. This slow growth rate allows you to repot your cactus at least once every 2-4 years to ensure it doesn’t overgrow its container and become root-bound.
Taller cacti species, such as the Myrtillocactus geometrizans or the blue myrtle cactus, can grow relatively faster, requiring repotting every 2 years.
Regardless of the species, cacti generally like a loose, fast-draining substrate, such as a mix of sand, pumice, and perlite. This combination is typically nutrient-scarce, but luckily for cacti, they don’t feed on nutrients a lot. They can thrive by receiving fertilizers only once (or thrice) a year.
As such, some novice gardeners might not feel the need to fertilize or repot their cactus at all.
However, waiting too long to repot your cactus can cause root-binding issues, nutrient deficiencies, and even promote pest infestations. Moreover, flowering tropical cacti species may need more frequent repotting (every two years) because they need richer soil than desert cacti species.
You should make regular repotting a habit to boost your cactus plant’s overall health.
Signs Your Cactus Needs Repotting
Cacti are sturdy plants that don’t require much care in terms of water and fertilizers. When placed in an area with adequate sunlight and given a regular watering routine, these plants can thrive for many years in an indoor space without needing much else.
However, you’ll know when your cactus is unhappy in its pot and will need a new one when you see the following signs:
1. Roots Growing Through the Drainage Holes
Roots growing through the drainage holes of your cactus’s pot is a tell-tale sign that your plant needs to be repotted.
The roots of a cactus can only grow for so long in one container. After a while, your cactus will outgrow its container. And if it stays too long in a pot that is too small for its roots, the roots will grow in circles around the container until the root mass is bound together and cramped.
While this might not seem like that big of an issue, root binding is a significant problem that can cause adverse effects. A root-bound cactus will have trouble distributing water and nutrients throughout the plant, which can negatively affect the plant’s health and even lead to death if not corrected in time.
Repotting is a quick and easy way to address a root-bound cactus. By providing your plant with a new container, its roots will have room to grow and unwind.
However, it’s best to repot your cactus before it becomes root-bound, exactly why you should stay proactive with your repotting habits and provide your cactus with a new container every 2-4 years. That way, you can prevent root binding and keep your cactus healthy.
To learn more about root-bound cacti, check out my article, where I discuss how you can tell if a cactus is root-bound and whether you should replant it: Do Cactuses Like to Be Root Bound? What You Need to Know
2. Growing Aerial Roots
Another sign that your cactus should be repotted is the growth of aerial roots, which are small, thin, branch-like roots that sprout from the parts of your cactus that are above the ground rather than within the soil. These roots are usually a light pink, brown, or white color.
A plant will grow aerial roots if it’s not getting all of its needs met in order to absorb carbon dioxide, water, and nutrients from the air. While the roots themselves are not harmful, they are a sign that you should make a few adjustments to your plant care.
One reason why a cactus might grow aerial roots is that it needs to be repotted. If your cactus is in a container that’s too small for its size, it won’t have enough access to nutrients in the soil to support it.
While aerial roots can be caused by other issues as well, repotting is always a good idea if you notice the growth of these roots.
To learn more, I recommend checking out my guide on cacti and aerial roots. You’ll discover what causes the condition and what you can do about it: Why is Your Cactus Growing Aerial Roots? 6 Causes
3. Withering or Discoloration
A withering or discolored cactus is a sign that you need to repot it as soon as possible.
Your cactus is withering if it is gaining a yellow or yellowish color, appears shriveled, or is either too wet or too dry. All these indicate that your cactus is not doing well and can do with some environmental adjustments.
Again, if a cactus has outgrown its container, its roots will not have enough space to grow. And if a cactus has fewer roots than needed to support its size, it can experience some serious deficiency issues, as the roots will not be able to meet the plant’s nutrition and hydration demands. Withering can occur if these requirements are not adequately met.
While withering can also be a sign of over or underwatering, or even some cactus diseases like bacterial or fungal rot, it can also be a clear indicator that it needs to be repotted.
4. Lopsided Growth Disproportionate to Pot Size
Another sign that repotting is long overdue is when your cactus is disproportionate to its pot size or appears lopsided.
This is one of the easiest ways to tell if your cactus needs to be repotted. If your cactus is simply too big for its container, it will need a new one to stay healthy and access all the nutrients and hydration it needs.
Keep in mind that most indoor cacti will do well in a container an inch (2.5 cm) wider than the plant in diameter. If you can’t see the potting mix anymore or the narrow spout of the watering can can’t make it through the gaps between the succulent stems, it’s time to repot your cactus.
5. Your Cactus Has a Disease
If your cactus has a disease, repotting is a great way to rid it of the infection, promote healing through healthier root growth, and give it a new, clean space to thrive.
There are many cactus diseases out there, most of them being viral, bacterial, or fungal. While additional treatment is always necessary, repotting can provide your plant with a clean space to heal and grow free of contaminants.
Think of it as making your bed with clean sheets or cleaning up surfaces to prevent the spread of harmful microbes. While the disease will need to be addressed separately, repotting your cactus boosts the chances of successful recovery significantly.
6. Pest Infestation
Another sure sign that your cactus needs to be repotted is if it’s infested by pests.
Here are some signs that your cactus might have pets:
- Appears shriveled or withered
- Yellow or sickly parts
- Brown spots (usually a sign of spider mites)
- Swarmed by small flies (fungus gnats)
- Unhealthy, chewed-up leaves
- Scaly appearance
Pest infestations need immediate treatment before repotting your cactus. For instance, you can manually remove the pests, like aphids and mealybugs using tweezers and drop them into a tub of soapy water. You can also wipe them off using cotton balls soaked in rubbing alcohol.
If the spines are too long and there’s little surface area to wipe the cotton balls on, you can use a highly diluted neem oil solution with 1 teaspoon neem oil, 1 teaspoon Castille soap, and 1 liter (0.26 gal) of distilled water. Spray this solution on your cactus and wipe it on the foliage of other infested houseplants to eliminate the pests in your indoor garden space.
Once treated, you can observe any more signs of pests. If cleared, repot your cactus in a fresh and sterile potting mix. This will give your cactus a fresher environment and free it from infestations that could have been in its previous soil.
Pro-tip: Treat the cactus before repotting. A newly repotted cactus will struggle in its new environment more if it’s also trying to fend off pest attacks at the same time.
If you’re repotting your cactus for reasons involving pests, you can mix in a little bit of cinnamon with the new soil to work as a natural pesticide that won’t harm you or your plants.
How to Repot a Cactus
This section will elaborate on the exact steps you need to take to successfully repot your cactus without damaging the plant, as well as provide tips on how to make the process easier.
1. Choose the Right Soil
Before you start the repotting process, the first thing you want to do is choose the right soil.
Soil selection is one of the most crucial parts of repotting. Without the right soil, your cactus can face tons of drainage and nutrition-related problems that can negatively impact its health. This is why choosing the right dirt is important, especially a mixture specifically designed for cacti.
Desert cacti can do well in a loose potting mix composed of sand and perlite. They need excellent drainage and don’t need many nutrients. Feeding them with weak fertilizers 1-3 times a year should suffice.
On the other hand, tropical cacti need richer soil with a bit of moisture retention. To provide these qualities, you can add 10% coco peat into the standard cactus mix. Coco peat can hold moisture and nutrients from fertilizers better and release them when the roots need them.
2. Select a Good Pot
Once you have the right soil on hand, it’s time to choose a good pot. There are two factors to consider: size and material.
When repotting your cactus, it’s vital to make sure your pot is the right size. A good rule of thumb is always to make sure the pot is 10% larger than the cactus’s diameter.
For better idea as to how big that is, you can refer to the following:
- Compact and globular indoor cacti species can use a new pot 1 inch (2.5 cm) wider than the previous pot when repotted after 2 years or 2 inches (5 cm) wider in 4 years.
- Moderately fast-growing indoor cacti like the blue myrtle and silver torch will need a new pot 2 inches (5 cm) bigger every 2 years, depending on how quickly they grow in your home environment.
- Flowering tropical cacti (like the mistletoe cactus) that bloom every year can use a pot the same size when repotted during the growing season. More than pot size, you need to replenish the soil nutrients to encourage them to bloom again. You can upsize the pot by 1 inch (2.5 cm) only every 2-3 years.
While size is very important, it’s also critical to get the right kind of pot. Water drainage is one of the most important parts of plant care, as a lack of adequate drainage will lead to root rot and even drowning. You should always purchase pots with drainage holes at the bottom.
You can either buy a terracotta pot with drainage holes and a matching tray or keep your cactus in a plastic container with adequate drainage holes within a more decorative pot, like a ceramic one.
The pot will work if it’s the right size, has drainage holes, and has something to catch the water leaking out.
3. Mix Soil With Perlite for Drainage
If your potting mix doesn’t have it yet or if you’re making a homemade cactus mix, you can amend your soil’s drainage by adding perlite. You can add one part perlite to one part soil.
This additive is great for making sure your soil has the ability to drain water correctly, which is good for cacti’s health, as they survive on little water, and too much water retention can cause a lot of issues.
4. Water Your Cactus 2-3 Days Before Repotting
This step will ensure your cactus is well-hydrated and wouldn’t need more moisture immediately as it settles in the new pot. Doing so will reduce the risk of transplant shock and improve the chances of survival. It will also make it easier to remove the cactus from the potting mix.
5. Use Gloves to Gently Remove the Cactus
For this step, it’s vital that you wear gardening gloves. Doing this will help protect both you and the plant. Most cacti have sharp spines that can be painful to the touch, so it’s really important to make sure your skin is covered.
For those with really long spines, you can also use a pair of kitchen tongs to hold the cactus as you slide it out of the old pot.
Once your gloves or tongs are ready, follow the steps below:
- Loosen the potting mix along the inner edges of the pot.
- Hold the cactus at the base as you tilt the pot to slide the potting mix and cactus out.
- Carefully remove the old potting mix from the old roots using your gloved fingers.
But if you’re certain the old soil wasn’t contaminated, you don’t have to remove it. The goal is to minimize the disturbance on the root ball.
6. Hold the Cactus Inside the Pot and Fill With Soil
Don’t dig a hole in the pot and shove the cactus inside, as this can damage the roots. Instead, prepare the pot and the new potting mix separately.
The best way to go about doing this is to hold the cactus inside the new container, holding the top of the roots about an inch (2.5 cm) below the top of the pot. Then fill up the pot with the fresh potting mix, covering the roots with about 1/2 inch (1.25 cm) of soil.
It can be tricky to do with only one set of hands, so it might be helpful to get assistance during this step.
Afterward, make sure to pat the potting mix down gently. You want to pat it enough to hold the cactus in place but not so much that it crushes the roots.
7. Wait 10-14 Days Before Watering Your Cactus
Once your cactus has been correctly repotted, it’s really important that you wait 10-14 days before watering it again. Watering it a few days before repotting gives it enough moisture to thrive for the next couple of weeks before it will need some more.
Repotting is a necessary part of cactus care, but it can be a traumatic experience for the plant and cause it to go into shock. It’s important to make sure it doesn’t have to deal with overwatering, which can lead to root rot. Cacti, after all, are drought-tolerant and wouldn’t mind
When it’s time to water your repotted cactus, water it deeply and let the pot sit on a drip tray. Wait until all the excess moisture drains out of the drainage holes before putting your pot on its saucer.
Should You Repot a New Cactus After Purchase?
There is a common saying in the cactus community that you should always repot a new cactus after purchase. Is this really true?
You should always repot a new cactus right after purchase. This is a good habit to practice because standard nursery soil isn’t adequate for a cactus to stay in for a long time. Repotting new cactus is also a good way to rid your cactus of any potential pests it could have obtained at the nursery.
Another reason to repot a new cactus immediately after purchase is to put it in a more suitable container, as paper or cardboard nursery pots are usually not meant for long-term use and will degrade over time.
And considering a new cactus will need to acclimate to a new environment, it’s best to ensure you get the ideal pot from the get-go. If unsure about the best pot for your new plant, don’t hesitate to ask the expert you are buying from.
Repotting is a fragile but necessary part of proper cactus care. However, it can be challenging to know when it’s time to repot your cactus.
If your cactus is root-bound, has sprouted aerial roots, is withering, is top-heavy, has pests or disease, or simply hasn’t been repotted for a couple of years, then it probably should be repotted.
Hopefully, this article has helped you better understand the repotting process and your cactus as a whole. By following these tips, you can successfully repot your plant and ensure that it lives a long, happy, and healthy life for years to come.