In this post, we will talk about soil requirements for cacti. We will discuss the best soil for cacti – which ones to buy or how to make your own homemade cactus soil. We will also talk about sterilizing cactus soil, and discuss each ingredient that can be used for making a soil mix. Please note that each type of cacti has its own soil requirements, and you can find general information in the post.
Should I buy or make cacti soil?
You should try making your own cacti soil even if you are a beginner. The problem with potting mixes for cacti is that they not suitable for each type of cactus. If you want to potentially have a collection of cacti in the future, making your own soil and experimenting is a way to go. When experimenting, make sure to follow general guidelines.
Most of the time, making your own soil mix for cacti will be cheaper than buying a bag of a potting mix. This is especially true if you have multiple plants. But if you decide to buy cacti soil, make sure it is suitable for your group of cacti (desert, jungle and others).
It is a good idea to buy ready a potting mix if you don’t have many cacti, any time to make the soil or don’t want to experiment (and potentially kill few plants during this process). All cacti hobbyists experiment with making soil mixes and see what works best for them.
Few of the soil mixes that you can buy for your cacti are:
- This Bonsai and Cactus Gritty Mix like this.
- Succulent and Cactus soil mix that is soil-free – you can add some sand for desert cacti and charcoal.
- Cactus soil mix that contains coir, perlite, pumice, sand, and stalite
Soil texture is very important for cacti
Different types of cacti will need a different type of medium/soil to grow in. The medium will be similar, but there will be some differences in soil mixes for desert, epiphytic, lithophytic cacti and others.
Apart from specific soil ingredients, cacti require a specific soil composition and texture. Having said that, it is important that cactus soil is airy and quite loose, especially when wet. Cacti soil must allow good drainage and airflow. What is more, the soil mix should soak in the water and re-wet very well.
What is more, naturally most desert cacti grow in soil that is low in nitrogen. Too much nitrogen in the growing medium can cause your cactus to grow very fast, causing the stem to stretch and spines to weaken. Cacti soil must not contain any manure, as it will lead to growth of fungus that cacti’s roots cannot fight. And, don’t use any organic fertilizers for cacti (except for epiphytic cacti).
Importance of pH levels in cacti soil
Almost all cacti require an acidic soil to grow and thrive. Some cacti species will need higher acidity soil than 
others. Generally, you need to make sure that the cacti soil mix is in the pH range of 5-6. Genus of Epithelantha, or button cacti, can do well in a more alkaline soil mix with pH levels of 6.5.
But generally speaking, any soil mix with pH that is less than 4 and higher than 7-7.5 will cause death of cacti. This type of soil mix is not suitable. If you have prepared a soil mix and pH levels in it are too high, you can lower pH levels by adding some peat.
But note, that there are different types of peat and some are more acidic than others, so you will need to add it gradually, then mix and check again.
To determine pH levels in the soil, you can use a meter that measures moisture, pH and light levels like this.
The best ingredients often used for making cactus soil
- Peat – it is one of the main ingredients for making a cacti soil mix. Peat makes the cacti soil mix porous and lowers the pH levels. The only downside that peat can bring is difficulty with soil re-wetting.
- Pumice/perlite – choose one of these ingredients to make your soil mix airy. Perlite is usually more available for sale and is easier to find. One of these ingredients is essential to let the water travel in the soil mix.
- Gravel/lava rocks – gravel or other rocks will be coarse and will help to make the soil mix loose and airy.
- Sand – sand will also help to make your cacti soil airy. Make sure to choose coarse sand.
- Potting soil – you will need potting soil to mix with other ingredients. You can buy some ready standard potting soil or make it yourself – mix peat and sand.
- Coir – it will help retain moisture in the mix and will provide structure. Use to replace peat moss.
- Turface like this– which is high fired calcined clay. This ingredient will promote good drainage and water flow in the soil. Can be used instead of gravel or other rocks.
- Charcoal – charcoal is a soil conditioner that will help prevent diseases by absorbing impurities.
So, how to make a homemade cactus soil?
You will need to prepare cacti soil depending on the type of a cactus you have – desert vs. jungle (hot area inhabitants vs. cacti inhabiting rainforests).
The soil mix for cacti will be following:
- 2 parts of a ready potting mix or made at home. To make your own potting mix add sand, perlite and peat mixed together (0.5:1:1). If you buy ready soil and it doesn’t have perlite/pumice, add it yourself. You can use coir instead of peat. Desert cacti need more sand, so add less for other types of cacti.
- 0.5 part of turface or gravel/rocks
- Some charcoal – few spoons
- Some fertilizer such as bone-meal or egg shells. Add around 1 teaspoon per 3 quarts.
You can experiment with different ingredients and see what suits you the best. You will also need to see what ingredients are available to you. When potting your plants, add some more gravel/rock to the bottom of the pot to avoid any potting mix from coming out from the drainage holes.
Epiphytic cacti naturally grow on and around the trees by attaching themselves to tree branches for support. These types of cacti prefer soil that gives them more support and holds moisture for longer.
So, for epiphytic cacti add more peat in the soil, or even better – orchid bark that will make the soil airy but will also provide support and retain the moisture. Desert cacti will need more sand.
Decorative rocks for cacti pots
You can also add some decorative rocks on the surface. But make sure they don’t prevent water flow and saturation. This will often suit cacti that you water from the bottom.
Sterilizing cacti soil before using it
As we have discussed, cacti are often very sensitive to any bacterial or microorganism growth in the growing medium. This is especially true if you use ingredients from outdoors or have bought them.
If the soil mix is contaminated, it will cause death of a new cactus or even spread of the infection to other cacti. This is why it is a good idea to sterilize the soil mix before using it. One of the ways to sterilize the cacti soil mix is by heating.
To do this, place the soil mix in a glass container or a pot, place it in another large pot with hot water and keep it on a slow cooking mode. This method is also called bain-marie. Keep heating the water inside the pot until it reaches a boiling temperature of 100 degrees Celsius (212 Fahrenheit).
This can take 20-30 minutes, depending on the amount of water. After it has reached boiling temperatures, turn the cooker off and leave the soil mix to cool down. A good tip is to leave the soil mix outside for few days before potting your plants.