What is Cactus Compost and How is it Made?


This post will address cactus compost to include succulents, of which cacti is a single subgroup. All cacti are succulents, but not all succulents are cacti. Growing succulents is an enriching hobby – or business. With over 10 000 species, there is both great variety and beauty to be had.

Cactus compost refers to the growth medium used for cacti or succulents. Experienced growers insist that making these mixes is part of the craft, creating a species and age-specific balance between pH, nutrition, and drainage.

Succulents are growing demand, with 3,000 species now requiring some protection under CITES (Convention on the International Trade of Endangered Species). As a valuable commodity, you want to make sure that you get growing them right.  This post will help you do that.

Endangered Cacti and Succulent Plants

CITES protects four major succulent plant groups:

  • The cactus family (Cactaceae); Cactaceae is by far the most prominent and best-known group and includes over 2,000 species.
  • The succulent Euphorbia species (Euphorbiaceae) include over 700 succulent species from 2,000 in the Euphorbia genus.
  • The genera Aloe (Liliaceae) – 400 species
  • The Pachypodium (Apocynaceae) – 14 species

Virtually every North American and European home has had a cactus plant on its kitchen window sill – most likely a  brightly flowered cultivar of Schlumbergera, the Christmas Cactus.

Except for one genus, cacti are unique to the Americas. Stems distinguish the Cactaceae family with specialized felted discs called areoles that grow spines, unique to this plant family. Mexico and the nearby south-western United States are the “hot region” for species variety, with approximately 30% of cacti genera being endemic and nearly 600 native species. Secondary diversity hotspots include Brazil, northern Argentina, Bolivia, Peru, and Chile.

The consumer market for succulent plants, for example, has been fueled by the demand for desert plants for landscaping. TRAFFIC Between 1998 and June 2001, North America estimates that they gathered almost 100,000 succulents worth $3 million in Texas and Mexico to feed the landscape garden market in Phoenix and Tucson.

In the Aloe market, Canada, the Republic of Korea, and Spain have exported the largest quantities of artificially propagated plants. The major markets for live plants are the United States of America, China, and Switzerland.

Deserts are very dry places, but plants can still grow there. Desert plants collect and use water in special ways.”

– Julie Penn

Cactus Compost Ingredients

Generally, succulents need nutrient-rich, well-drained soils. You can get an optimal mix by combining different ratios of organic matter and inorganic matter (ofter referred to as grit). What the ratio ought to be and what elements should be present seems to be a matter of opinion, even among specialists.

The fun part is developing what works for you. Below I provide quite a bit of guidance and some base-mixes which you can adapt for your use.

A word of caution: commercial potting soil claiming general purpose is a possible starting point, but mixing your own is better. You want to focus on how much organic matter and drainage your soil has. Also, you want to avoid unquantified fertilizer inclusion. Ideally, you want to be in control of as many variables as possible.

Standard materials are listed below in the two groups, with a brief explanation of each’s function in the mix.

Organic MatterDrainage Enhancers
Coconut CoirPerlite
CompostCoarse Sand
Forest ProductsDecomposed Granite
Potting SoilHorticultural Gravel
Top SoilChick Grit
Kelp PelletsTurface for Plants MPV
Carbon Activated CocoPeatExpanded Shale
Peat MossPumice

Organic Matter

Coconut Coir

Coir helps retain water in dry soil, improves soil drainage, is slow to break down (4 years), and creates pockets of air around the roots of plants, allowing excess moisture to drain away. It is 100% organic and eco-friendly, free from soil-borne pathogens and weeds. It has a pH of 5.5 – 6.2.

Compost

Made by decomposed organic materials, compost enriches and enhances the soil. Plant nutrients and helpful organisms like worms and fungal mycelium are abundant in the final combination. In gardens, landscaping, horticulture, urban agriculture, and organic farming, compost promotes soil fertility.

Forest Products

These are items like barks and leaves in a state of semi-decomposition. Semi-decomposed leaves and bark can act as a water-storing sponge. Bridging the gap between organic matter and grit, forest products provide both nutrition and good drainage. Ideally, the particle size should be limited to a quarter-inch and exclude dust.

Potting Soil

Potting soil provides soil with increased organic matter and drainage. Typically, potting soil may have some perlite included. Some potting soils may include fertilizers and are then not suitable for succulents.

Top Soil

Topsoil is a cheaper option than potting soil. Topsoil comes from sites where the top 4 to 6-inches of the surface have been removed, commonly using a grader, and then bagged for resale. Interstate regulations exist for soil migration.

Topsoil includes less organic matter than potting soil and thus has poorer drainage capacity. Some purest insist on its inclusion in the mix in fear that commercial potting soils may include fertilizer. Excess nitrogen causes succulents to have misshaped leaves.

When using potting soil, rinse it and let it stand in the sun for 3 to 4 days to sterilize it, stirring it occasionally.  If the weather isn’t conducive to this process, sterilize the soil in an oven for 20 minutes at 200 degrees Fahrenheit, stirring it occasionally.

Kelp Pellets

Including kelp pellets or granules in the mix is an excellent fertilizing option. Kelp typically has 4 percent nitrogen, no phosphate, and 2 percent potash. Its inclusion in a blend is less than 5 percent of the total mix volume.

Carbon Activated CocoPeat

I have read that some growers include a carbon-activated cocopeat – a coconut coir brick that has some activated carbon included. Food manufacturing processes more commonly use activated carbon, mainly as a filter. Its use in horticulture is gaining popularity as a pathogen inhibitor.

Peat Moss

I added peat moss to the list to have the opportunity to advise you NOT to use it. Peat moss has a low pH (acidic), and most succulents prefer a pH range between 7 and 8 (low alkalinity). Also, peat moss can cause anaerobic conditions – something succulents cannot tolerate.

A picture of hands holding potting soil

Inorganic Materials

Perlite

Perlite is an amorphous volcanic glass that has relatively high water content. Heating the crude rock to 1600 degrees Fahrenheit causes it to pop like popcorn resulting in a light material with excellent water absorption properties.

Perlite particles also interface with each other and other soil constituents to create air passages. These air passages provide oxygen to roots and allow excess water to drain rapidly.

Coarse Sand

Do not use fine sand or beach sand. The coarser, the better.  It must be able to aid in better drainage.

Decomposed Granite

Decomposed granite is a product of the effect of weather on granite blocks. Use pebbles not larger than a quarter-inch in diameter for aeration and to assist drainage. If you sieve it and get a slightly larger couple, use them to create a rocky aesthetic cover that will prevent rapid evaporation from the soil.

Gravel

Instead, use decomposed granite as the gravel may have sand particles. Washing it and leaving it to stand in the sun for three to four days to sterilize is a solution. Particle size should be less than a quarter of an inch in diameter.

Chick Grit

Chick grit is typically fed to chickens to help process food in the giblet. It has an orange color and can either assist drainage and aeration. It is also a decorative feature on the surface, creating a great color offset to the succulent’s color.

Turface for Plants MPV

Turface is a brand name for a product commonly used on baseball pitches. Often referred to as fired clay, it also contains silica and bentonite – both ingredients for moisture regulating potting soil.

With a total porosity of 74%, this product is a favorite for many succulent growers. The MPV version seems to be preferred.

Expanded Shale

Expanded shale:

  • has good insulating properties,
  • increases soil porosity,
  • absorbs 38% of its weight in water,
  • durable for decades,
  • does not change pH,
  • improves drainage and aeration (retains 30% air space),
  • 100% inert, inorganic so it does not decompose

Expanded shale can soften up hard clay soils and make them more workable. Its porous structure allows aeration from shale particles, resulting in a more widespread and healthier root system in poorly aerated clay soils.

Pumice

Pumice is solidified foam that forms from lava rich in gases. It has numerous pores in the form of bubbles and irregular cavities that absorb moisture. For planting succulents, you want a 3/8 x a quarter-inch mix.

The Essentials of Growing Cacti and Other Succulents.

Succulents grow naturally in semidesert conditions, the Alps, and in jungles. Each group has developed unique adaptations to survive often harsh environments. What sets succulents apart from other plant species is their ability to store water – up to 99% of the plant may be water. For the most part, there are three environmental elements to consider to have a successful cactus growing experience. These are:

  • Soil
  • Water
  • Light

Let’s look at the three environmental elements in these climates; Semidesert, Alpine, Jungle.

Semidesert Climate Cacti and Other Succulents

Except for one genus, Rhipsalis, which has a distribution that stretches from South America to southern Africa and Sri Lanka, cacti are unique to the Americas. Stems distinguish the Cactaceae family with specialized felted discs called areoles that grow spines, special to this plant family.

Desert cacti thrive in arid regions but not in desert dunes. The belief that cacti can survive with no water for extended times is inaccurate.

In layman’s terms, there are three groups of semidesert cacti:

  • small rounded, flat, or cylindrical plants
  • shrubby, segmented, and sprawling kind
  • large columnar and tree-like giants

The guides within this article are generalized for a regional-specific growing environment. The tricky part of successfully propagating these plants is taking the provided guidelines and adapting them slightly to your environment and species.

Soil For Semidesert Cacti

Most cacti prefer nutrient-rich, rocky soil with good drainage. We’ll utilize some of the same components I used for the jungle cactus and some new ones to make a proper growing environment for our desert cacti.

I use a simple, well-draining blend of a 50/50 split of organic/inorganic materials for semidesert climate cacti.  

  • 25 percent Potting Mix with no added fertilizer
  • 25 percent Coconut Coir
  • 20 percent Expanded Shale
  • 20 percent Turface
  • 10 percent Pumice

Don’t be tempted to switch the potting mix with peat moss. Peat moss is hydrophobic and difficult to re-wet. Also, be sure that the potting mix does not have any added fertilizer, as this will negatively affect the leaf growth of your succulents.

Ideally, use a terracotta pot because it allows air and water movement through its walls.  All pots must have draining holes, and these should not be covered. Test your mix for water retention and flow. Do not use stones or pebbles at the bottom of the pot.

When watering your pot, water should not sit on top but should readily flow through the planter. Due to capillary action, some water will remain in the soil, but your mix of coconut coir and the other gritty material will ensure that the roots are not waterlogged yet retain some moisture.

How much water does semi desert cacti require

Cacti’s ability to thrive in scorching, arid, and harsh environments is quite remarkable. But they do need water – water is essential for all cacti to live. Their ability to survive in locations where water is scarce or given infrequently has earned them a reputation for drought resilience.

The majority of desert cactus can withstand prolonged drought, mainly because the last time they had access to water, they crammed as much as they could into their tissues. Cacti also have several characteristics that allow them to retain moisture and avoid drying out in hot environments.

When the earth is dry, it’s an excellent time to water desert cactus, whether they’re in a pot or the ground. Watering once a week is suitable in hot, dry locations such as southern California in the summer. It may take three to four weeks for the soil to dry out enough to merit more water in more humid or cooler places.

The goal is to minimize overwatering rather than avoid watering altogether. It is still preferable to submerge rather than over-submerge. If the soil is still wet, don’t water it. There are exceptions to every rule, so you’ll have to experiment to find the optimal watering regime for your plants, just like you did when picking the correct soil.

Stand the pot in a bowl of water up to the soil level until the soil mixture is soaked, then remove and allow it to drain freely. (Try not to forget about the planters in water; otherwise, they may decay.) Use your finger to feel the soil once the top half-inch of the potting mixture is dry again.

Do not spray mist these plants; they are desert, low-humidity plants.

Different Light requirements for Cacti

Desert cactus, in contrast to jungle cacti, prefer a lot more light. Potted plants, seedlings, and newly rooted cuttings should only spend half of the day in the sun. The light would quickly destroy plants that aren’t well-established.

As a result, it is not a good idea to transfer cacti into direct sunlight until they have established a healthy root system. Avoid full sun even for established potted plants.

You’ll rarely find a position where your cactus gets too much light if you’re growing your potted plants indoors. The inverse will rather be true. You may use full-spectrum fluorescent lights to augment or replace sunlight when natural light is scarce.

If your cacti require extra light, you’ll be able to notice right away. Cacti with insufficient light will have thin, stretched-out growth.

Colorful picture of Succulents

Alpine Climate Succulents

All the succulents that grow in mountainous regions require loose soil that is often volcanic in nature. The most significant risk to their perishing is lack of light or overwatering. A typical mix for the plants that grow in mountain regions would be well-drained and allow roots to grow and air to circulate. If these qualities are not present, succulents are prone to root rot, which often results in the death of the plant.

Although commercial succulent potting soil is widely available, preparing your own ensures the mix’s quality and allows for experimentation. Depending on the batch size, combine ingredients in a large bowl or bucket. Measurements are generally volumetric and not by weight.

Soil

A starting basis for Alpine climate succulents would be a 30/70 mix of organic/inorganic material. The base recipe would look as follows:

  • Two parts coconut coir
  • One part of clean sand, preferably well sterilized
  • One part of perlite
  • Add 2 ounces of limestone and two ounces of bonemeal for every 4 gallons of the potting mixture

Limestone is rich in calcium and magnesium and balances the soil pH. Bone meal supplies phosphates which stimulate root growth.

Light

One of the most prominent reasons for the failure of growing succulents from the Andes all the Alps is too little light. However, try to avoid drastic light changes. Succulents will stretch if they do not have enough light to reach the light.

Jungle Climate Succulents

Jungle cacti include species in genera:

  • Acanthocereus
  • Disocactus
  • Epiphyllum
  • Hatiora (Easter Cactus)
  • Hylocereus
  • Lepismium
  • Rhipsalis
  • Schlumbergera (Chrismas Cactus)
  • Selenicereus and perhaps a few others.

Soil

The majority of Jungle cacti are either lithophytic or epiphytic, which means they grow on rocks or in trees. This plant draws its nutrients from the air or dead leaves and other debris accumulated in nooks and crannies. It’s worth noting that there aren’t any parasitic cacti. Those that grow in trees do so for support, but they do not deplete the host’s nutrients. We’ll want our soil to mirror these natural circumstances for the best results.

Here’s a good mix with the essential ingredients for Jungle climate cacti. Remember, this is merely a suggested starting point. The vital needs are some acidity, some forest material, and good drainage.

  • 30 percent coconut coir
  • 15 percent forest material – Fir bark (also called Orchard bark)
  • 15 forest material  – Oak Leaf Mold – for acidity
  • 20 percent pumice
  • 20 percent decomposed granite

Remember that the orchid bark will eventually decompose into the soil. The result will be a vibrant soil that may not be as effective at keeping the roots healthy as it should be. It’s not a bad idea to re-pot these plants with the new ground every two or three years.

After your plant has completed blooming, this is the perfect time to do it. It will be ready to start developing again at this point. You might also add bone meal or kelp pellets to the new mix as a fertilizer.

Water

The ability to keep water from rotting the roots is dependent on well-drained soil. However, watering once a week is a good rule of thumb with suitable soil, though exceptions. During long periods of hot, dry weather, you may need to do it twice a week.

When it’s cool and rainy, on the other hand, you might only need to water every two weeks. Watering requirements for indoor plants should be more consistent. Due to the dryer air produced by using the heater, folks who live in colder climates may discover that they need to water their indoor Jungle Cactus more in the winter than in the summer.

These plants resemble the ‘Christmas’ cactus in appearance and lack genuine spines. If this is the variety you have, they want a little more water, so water frequently over the spring and summer to keep the potting mixture moist.

Because these creatures are from humid jungles, misting them often, even daily, keeps them happy. Just check with your finger the first half an inch. If it’s dry, water your plant. If it’s still damp, wait a day or two. Watch out for using moisture meters between plants and cross-contaminating pathogens.

Light

Jungle Cacti can withstand a wide range of lighting conditions. However, rather than just surviving, we’ll assume that the goal is for plants to thrive. Plants require a certain amount and intensity of light to thrive. Full morning light followed by afternoon shade is the optimal condition for Jungle Cacti. Your plants will flourish as a result of this.

Other conditions may be:

  • Morning shade/full afternoon sun
  • Full shade
  • Full sun

Your plants will often take on a yellowish color and may develop spots if they are in the shade in the morning and full sun in the afternoon.

These effects will be significantly more noticeable in direct sunlight. There are exceptions like most things in nature, and certain plants enjoy and flourish in full sun.

The plants will appear dark green and healthy in complete darkness, but their stems will be stretched out long and thin in an attempt to get more light.

A plant may proliferate and produce numerous show-quality stems in perfect conditions, but it will not flower. Exposing the plant to more prolonged and more intense sunshine will cause it to blossom in this case.

Picture of a bunch of different succulents

FAQ

Conclusion

Growing succulents, including cacti, is very rewarding. Every plant is unique, and every species has its demands. Once planted in the right soil and the right lighting environment, they continue giving year after year.

The effort to get the cactus compost mix right is worth every investment made of both money and time.

I trust you enjoyed this article and that it shed some light on succulents in general and on cacti specifically. Mix your cactus compost and see what all the fuss is about.

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Tony O'Neill

I am Tony O'Neill, A full-time firefighter, and professional gardener. I have spent most of my life gardening. From the age of 7 until the present day at 46. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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