Choose the wrong type of soil, and your beloved cacti will die pretty quickly. So, what constitutes a healthy soil mix suitable for cacti plants? Hint: You can make your own cacti soil mix!
Cactus soil is mainly composed of coarse inorganic particles incorporated with a bit of organic base. The proper growing medium for potted cactus has excellent drainage, loose consistency, water retention, and provides just enough nutrients to the cactus.
A cactus potting mix should mimic the substrate in which cacti naturally grow – the desert soil. Basically, it has to be gritty and loose to achieve optimum growth for your plants. You can purchase the substrate or read more below to learn the tips on making cacti mix yourself.
The preferable proportion needed to make around 2 kg well-draining DIY cacti mix are:
- 6 cups pumice
- 1 cup perlite
- 2 cups coco coir
- 1 cup vermicast
Below you can find our amazon recommendation.
When making DIY substrate for cactus, always remember the basic concept. The soil mix should hold adequate water for the plant to absorb the needed moisture but only for a short time and MUST DRAIN out fast so the root system will not rot.
The good thing about making a DIY cacti mix is that it will give you control over your medium, so you can customize it according to your watering regimen, the pot you use, the climate you have, and the kind of cactus you are growing.
I live in the tropical Asian region, with abundant rainfall, high temperature, and high humidity. I will share the soil mix recipes I used for my cactus, 70% inorganic and 30% organic. Remember, what works for my plants might not work for yours.
You may opt to use other organic and inorganic ingredients. But here are the materials and their proportion that comprise my cactus mix.
The proportion I use for pumice is 6 cups for superb drainage and structure of the mix. Before using the pumice, I usually wash it under running water to eliminate the fine powder adhering to the stone’s surface and undesirable insects like ants and gnats. I dry them afterward under the scorching sun to kill potential bacteria.
Perlite keeps the soil loose and well-aerated, so I incorporate my mix with 1 cup of this inorganic material. If perlite is not available, I just mix in 1 cup more of pumice for added grit. When I handle perlite, I always wear a mask as it is pretty dusty, and I don’t want to breathe it in.
A mixture of 2 cups coco coir and 1 cup vermicast comprise the organic base of my DIY cactus medium. Coco coir holds adequate moisture, while vermicast supplies nutrients for my plant. I blend in 3 cups of their mixture to my DIY soil-less mix. I store my coco coir and vermicast in tightly sealed bags to prevent the intrusion of insects.
The so-called crumbly ball test is one expert trick to check if the cacti soil mix has a gritty consistency. Take a handful of the soil mix and squeeze as hard as to form a ball. The resulting ball or lump of the material should break apart with a minimal touch and not remain as a ball even when wet. That is a bench test for a good, gritty, well-draining cacti mix.
Above I gave you the gold recipe for cacti mix. But what about the materials you can find in many other cacti soil mixes (both from other DIY recipes and commercial ones). Knowing them will allow you to swap them if one of them is missing or create even a better one more suitable to your climate and water conditions.
Cactus soil (more correctly called mix) contains non-water retaining materials and non-compact. A limited portion of organic base ingredients and ample coarse inorganic particles are mainly used to attain a loose mixture that is free draining.
If you want a magical cacti mix formula, sorry to let you down, it does not exist! Cacti are pretty resilient plants, and until some basic needs are covered, many different cacti substrates can fit the purpose.
It is vital to use materials that provide satisfactory drainage capabilities. Take note that substrate that blocks water flow will soak and drown your plant’s precious roots. Remember, cactus roots do not like standing on wet feet for several days, leading to root rot, diseases, and insect infestation.
Can you use garden soil for cacti soil?
As much as possible, regular soil or dirt found in the garden should not be used as cacti soil. It contains pathogens harmful to the cactus, and it is way too water retentive for the sensitive cacti roots.
If blended appropriately, the materials below will work to make a suitable cactus soil.
Organic amendments hold moisture and nutrients. These ingredients come from plant debris such as pine bark, coco coir, peat moss, and compost.
Blending a small portion of organic matter provides a cactus soil the ability to absorb moisture well but without holding too much water (remember indeed to use only a tiny amount – how much? Keep reading). The absorbed moisture can be the source of hydration for the plant’s roots as the overall medium approaches dryness. Organic bases also provide nutrients for the plant as most of them have high nutrient value.
The amount of the organic-based compound depends on the environmental condition and cactus variety you’re growing. You will need a soil mix with more organic substance if you’re in a highly arid region. Furthermore, if you’re growing a cactus variety sensitive to too much moisture, opt for cactus soil with lesser organic matter.
Here are the organic materials often used for cacti substrates:
Peat moss is a common soil amendment widely used among commercial mixes. It improves water absorption without compacting the soil and can be used in minimal amounts in a cacti mix.
Benefits of using peat moss:
- Low pH value
- Good water retention
While cacti benefit from the low pH value of peat moss, using it in a significant amount is not beneficial to the plant’s roots. When peat moss decomposes, it begins to compress around the base causing severe problems to your cacti.
As the peat moss compact, it makes water and air circulation difficult. Once it gets completely dry, it is difficult to rewet peat moss.
Although peat moss is widely available, it is pretty expensive compared to other organic materials. Aside from being pricey, peat moss is non-renewable, and its production process involves several damaging effects on the environment. The majority of cacti growers quit peat moss and use the alternative coco coir as an amendment.
Coco coir is a lightweight and fibrous material obtained from a coconut husk. It is an excellent alternative for peat moss.
Benefits of using coco coir:
- Improves soil structure
- Provides good air circulation on the roots
- Holds water effectively
Cactus varieties such as Gymnocalycium love a little more moisture on their roots and would greatly benefit from coco coir. It has an excellent moisture trapping ability that makes the substrate moist. If you live in a region with a mostly dry climate, a significant quantity of coco coir will help keep moisture retention.
Here is an excellent coco coir product to amend to your gritty medium.
Pine bark is made by shredding the bark of pine trees or other evergreens.
Benefits of using pine bark:
- Provides structure; it does not compact.
- Create air pockets for air circulation
- Can lower soil pH
- Degrades slowly
Even though pine bark provides aeration, it lacks water holding capacity.
Compost is simply decomposed organic matter. It is a mixture of any organic materials such as bark, food scraps, and other plant matters thoroughly broken down.
Benefits of using compost:
- Excellent water holding capacity
- Contains beneficial bacteria
- Relatively cheap
- Provides nutrient
The increased water retention of compost provides moisture when your cactus needs it most. Using compost in your cactus mix boosts soil microbes growth which improves the quality of the medium, producing a healthier condition for your cactus. Compost includes composted worm castings/ vermicasts, composted carbonized rice hulls, and composted pine bark.
The inorganic materials that can be used in the cactus mix promote drainage and airflow. This is key for healthy cacti roots. Such inorganic materials are derived from non-living natural sources like rocks and minerals. Some options for non-organic components are pumice, lava rock, coarse sand, pea gravel, perlite, and vermiculite.
Incorporating the correct proportion of gritty inorganic particles to your cacti medium saves your plant from drowning upon watering. The porous mineral encourages healthy root development that grows freely due to the excellent air pockets it provides. If you’re growing cacti indoors, you may want a more gritty medium to prevent your plant from suffering from excess moisture.
Here are the viable options of inorganic minerals with their key benefits:
Pumice is a sponge-like volcanic rock with many tiny empty bubbles, so it is very light that sometimes floats on the water. It is the ideal mineral for the cactus mix.
Benefits of using pumice:
- Exceptional water and moisture absorption, but gradually release them
- It helps aerate plant roots
- Allows water to drain freely
- It makes the soil loose
- It has micronutrients that are good for cactus growth
While pumice stones have several advantages, it is not the most accessible product to find.
Lava rock is a molten volcanic rock that cools up and solidifies upon contact with air. Empty air pockets form upon cooling, making the material light and porous. Lava rock is packed with trace minerals and micronutrients.
Benefits of using lava rock:
- Maintain a significant amount of moisture
- Provides perfect drainage
- Supply plants suitable minerals and nutrients
- Improves soil aeration
Lava rock comes in two colors, red and black, and both work great whether mixed in the medium or as a top dressing. For uniform consistency, use lava rocks in 1/8-1/2 inch size just like the one below from Amazon.
River sand is a non-porous aggregate. Gardeners opt for coarse river sand for a more gritty medium.
Benefits of using coarse river sand:
- Ensures good drainage
- Lower price
- Widely available
- Add air space
Using river sand in large portions will prolong moisture retention and may result to root rot. When using sand in your mixture, don’t use just any sand such as play sand or beach sand as they are just too fine. Make sure you get the coarser texture sand.
Pea gravels are small, round, and non-porous stones. They are heavier than river sand and significantly larger than coarse sand.
Benefits of using pea gravel:
- Enhance drainage
- Add stability for top-heavy cactus
- Do not hold too much water
While pea gravel improves drainage, a large quantity will make the medium dense, preventing roots from growing freely.
Perlite is a non-renewable resource obtained from a volcanic eruption. It is incredibly lightweight and porous and can be an excellent alternative for sand.
Benefits of using perlite:
- Increases air space for the roots
The downside of using perlite is its lightweight property, and it tends to float above the soil mix upon watering. It cannot retain water due to its extremely high porosity property.
Every cactus grower has soil preferences suitable for the cactus variety they are growing. There are vast arrays of the pre-made commercial cacti mix available in the big box store and online stores like Amazon.
Below is a table of commonly purchased cacti soil in Amazon with its components.
|Cactus Mix Brand
|Calcined Clay and Fine Pine Bark
|Black Gold SunGro
|Pumice, Perlite, Softwood bark, and Vermicompost
|Miracle- Gro Cactus, Palm, & Citrus Potting Mix
|Sphagnum Peat moss, Forest Products, Perlite and Sand
|Superfly Bonsai Cactus & Succulent Soil Mix
|Akadama, Pumice, Pine Bark, and Haydite Clay
Bonsai Jack is a jackpot for water-sensitive cacti because it is super gritty. It has top-quality ingredients, using a large portion of calcined clay and a bit of fine pine bark.
This mixture results in an exceptionally loose and fast-draining substrate which is excellent for most cacti. Bonsai Jack is also suitable for indoor-grown cactus as it does not retain too much water that would cause root rot. If you are in an area where rain is frequent and humidity is always high, Bonsai Jack will make your roots stay dry.
Suppose you have a relatively dry and hot climate and may want to use Bonsai Jack. In that case, I recommend amending the mixture with a little more of organic matter such as coco coir and compost to hold moisture, or else you will have to water your cactus frequently.
With Bonsai Jack, you will need to feed your cactus plants twice every year because the mix itself does not have enough nutrients the cactus need.
Black Gold SunGro has pumice, perlite, softwood bark, and vermicompost. The components are primarily lightweight and porous, so expect that the substrate will drain excess water well.
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It contains pumice for drainage, but it also comprises organic materials that make drying time longer. This potting mix could be the suitable medium for cactus in dry, hot climates or for growers who always seem to forget to water.
Even if you have a humid climate, you can still use this mix, but you have to blend it with more pumice or other aggregates.
This cacti mix has an organic base ingredient of sphagnum peat moss and forest products, blended with perlite and sand.
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Its organic content fueled the medium with nitrogen, phosphorus, and potassium, while the minerals provided drainage and airflow. The peat moss does make the medium challenging to rehydrate once it gets dried entirely. You will need to water deeply to ensure that the water is absorbed.
Beginners tending to water frequently or growing moisture-sensitive cactus should amend this mixture with a good amount of inorganic particles.
Superfly Bonsai soil mix has a top-quality recipe with akadama, pumice, and haydite clay as the inorganic base and pine bark as the organic base.
It has adequate inorganic components to encourage water to drain freely, with a lesser organic mix to hold a certain amount of moisture. Like other substrates with a fewer organic content, fertilizing once or twice a year will equip your cactus with balanced nutrients.
A great cacti mix must be really gritty. A gritty mixture allows water and air to pass through easily and doesn’t turn into a solid mass as it gets dry (it does not cake).
Many newbie gardeners message me about the proper and best soil mix for their cactus. The truth is, no specific soil mixture will work for everyone else. The availability of materials in different areas will always vary, so what ingredients I have may not be accessible for you.
So, the best suggestion I can give is:
1- Right materials: Find materials that you can procure that meet the characteristics suitable for your requirements. Perhaps you have available compost from your backyard. It would make an excellent organic constituent. You just need to acquire the inorganic material, maybe from the nearest aggregate store. You can find tons of pumice from construction sites, but make sure to ask for permission first.
2- Adapt to the environment: Ensure the medium you make is suitable characteristics appropriate for your cactus. If you grow low-water cactus in a humid climate, do not make a mixture with so many organic materials that would retain too much moisture. Else, your plant will sit on a damp medium and end up rotten.
Work with what materials you have, or better yet, find suppliers that can supply the materials you need.
- Despite there is no absolute formula for cacti mix, a substrate that allows water to flow freely, gives adequate space for roots, and holds moisture for a short period is the ideal medium for cactus.
- Among the inorganic minerals viable as cacti medium amendment, pumice is the most beneficial and ideal particle for cacti substrate.
- When using pre-made commercial cacti mix, it is essential to determine if that cacti mix alone is suitable for the plant you are growing. If not, amend it with minerals or additives that are appropriate for your cactus.
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