Series 1, pg 3 – cacti and succulents

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mix for succulents



This is page 3 in the series on exploring different medium components you can choose for creating the proper habitat for your houseplants. This time we are planning to plant cacti and succulents and it is a good idea to know what part of the world your plant originated because these environments vary from dusty dry deserts to moist tropical forests.  Here are some tips to help keep your plants happy, healthy and growing strong.

by Mary Sue






      Here’s The Dirt…page 3

           Time to keep it light and get your hands dirty


When you know the needs of your plant you can combine any number of ingredients to create a perfect habitat or there are many commercial potting mediums based on the following components.  The ingredients you supply to your plant will dictate your plants growth.  Garden soil alone is unsuitable for containers because it may contain weed seeds, pests and diseases.  The drainage often becomes poor quickly without the activity of worms and other animals once you put it into a pot and place it indoors.  Finding materials to mix together to create the best environment for your houseplants has never been easier.  We will begin by exploring the many ingredients you can use in many combinations, this time for cacti and succulents, to create many different habitats.

Cacti and Succulents

Almost anything can be grown in a basic soilless mix but when it comes to cacti and succulents you may want to specialize.

I should define cacti and succulents a bit.  All cacti are succulents but all succulents are not cacti.  There are ways to know if your plant is a cactus by the fact that they have areoles (structure that spines, new branches, leaves, or flowers emerge from) which can be very small like those of the Christmas cactus.  If a cactus is wounded, sap will run clear but sap of succulents is milky.

Some cacti and succulents, like the barrel cactus, are found in dry desert locations, and have developed spines and thorns instead of leaves to reduce water loss.  They may have thick, waxy skins to hold water inside.  The 10-14 hours a day of sun and the wind will evaporate much of the moisture in the porous soil quickly.  Cacti may have shallow wide reaching roots so they can soak up as much water as possible when it rains or roots that travel many feet straight down reaching to underground supplies.  There is usually very little nitrogen in the desert ground so you probably wouldn’t add compost or humus to a potting mix for this plant but you may add perlite or pumice to be sure to have good porosity.

Others, like the Christmas cactus, are found in tropical forests of South America where the location has less sun to evaporate the moisture both in the ground and in the air so something like sphagnum peat or vermiculite may be called for to provide water retention.  The rainfall is also measured by the foot rather than in inches like the desert environment.  These plants can be nestled in the crooks of trees where plant debris like nutrient rich leaves have gathered.  This provides a good amount of nutrition that you will want to supply to your houseplant also.

Some succulents may find that a little compost adds to the greening or overall coloring and health of the plant.   Knowing the natural habitat of your plant will help dictate the medium you would like to provide.

Cacti and Succulent Ingredients

All can be pulled from lists previously given but I have selected a few here for your quick reference.

builders sand

builders sand


– coarse builder’s sand is used to improve drainage and will add weight to a container.  It has no nutrient holding value.  Be sure it comes from rivers or fresh water lakes as you do not want the salt.  When using this for cacti and succulents be sure to add more porosity and something to hold some moisture.




– a good coir mix will contain both the pith, fiber and chips.  Often used as a substitute for sphagnum peat moss for the environmentally conscious.  Seems to retain water well and supply the same aeration as a coarse sphagnum peat.  Mexican coir, readily available, is essentially free of sodium, is rich in potassium, has some anti-fungal properties and has a stable ph of about 5.98 depending on the grade.  Perhaps a better choice than sphagnum peat when planting up cacti and succulents due to the fact that these plants need to become quite dry between waterings and if you let a peat based mix dry out sufficiently you may have great difficulty getting it moist again.

sphagnum peat

sphagnum peat


– is still breaking down. Sphagnum peat is humus but so very broken down that very few nutrients remain and is beneficial in providing a constant acidity that will hold water like a sponge.  It is usually free from weed seeds and disease organisms.  Used to provide aeration, water retention and anchorage.  It is harvested mainly in Canada and Europe and does involve destruction of the natural habitat of many plants and animals. more




– made from heated volcanic rock.  Heating expands it and makes it lightweight and crunchy.  Approximate ph 7.0.  Provides aeration, water and some nutrient retention from fertilizers, will not break down (unless you crush it), and is lightweight for containers.  May want to add dolomite limestone when using to neutralize the notably high fluoride content so your plant will not be able to absorb the fluoride.



– made from cooled lava, porous, does not retain water and does not break down.  It does float to the top of a mixture but not quite as much as perlite.  Used to provide aeration.


– a clay pebble, comes in several sizes, has been heated to create a porous medium.  Used to provide support and aeration, often in bonsai and orchid mixes but may be used to aerate medium for succulents and cacti also. Holds moisture, with ph 7.0.  Sold under the names Aliflor, or Turface.  Use a window screen to sift out some of the more fine bits and rinse to remove dust before using.

medium size fir bark

medium size fir bark


– use pine, fir, cedar, or hemlock bark all under the size of a dime and smaller.  Used to aerate the medium and supply nutrients and minerals.

Use only the small pieces you see here.

Hardwoods break down more slowly than soft woods like pine and will not steal nitrogen from your mix as rapidly as it decomposes.



– reduces acidity and supplies calcium and magnesium.  Can neutralize the acidity of sphagnum peat and the fluoride found in perlite.


– organic matter that is still breaking down, supplying nutrients, aeration and will hold moisture.   Any of the following 3 ingredients can be added to a nice sterilized loam to provide the necessary food and aeration for most houseplants.  Perhaps do not use with a true cactus whose natural habitat is desert and go easy when adding to a succulent mix.

  • Composted animal manure – well-rotted manure is valuable as a soil conditioner, adds nitrogen and has a high population of good bacteria.
  • Decaying leaf mold – partially decomposed matter from the forest floor and is an excellent compost that is rich in bacterial life and organic fertilizer and should be used when flaky not powdery.
  • Decaying bark – partially decomposed from the bark of a pine or other tree.



– decomposed plant and animal matter.  It can enrich the soil with minerals, nutrients, raise the water-holding capacity or increase porosity and aeration depending on the source.  Mixing it with a clay soil may allow more air to circulate, mixing with a sandy soil may allow more moisture to be retained.  Mixing with anything will create an environment that stimulates the development of micro-organisms you need in a healthy soil.  It is generally well-decomposed, perhaps from lake bottoms and can be aerated with a larger particle matter, to make it more suitable for your plants, such as a coarse sand, pine bark fines, sphagnum peat moss (or coir which is replacing sphagnum peat for the more environmentally conscious). Humus from peat sedge may be too fine for container gardening and will pack too tightly around roots.  Know what the humus comes from.  more

Once you have chosen, mixed, and moistened your components, run it through your fingers and decide whether or not you feel it is porous enough for the water to run in and around your cacti roots and out quickly.   You can also purchase a cacti/succulent mix from the local garden center.  To this, for a cactus, I would add perlite or a very coarse sand to make it more porous.  If you know where your plant originates you will know if you need to add anything to make it just the right growing medium for a happy, healthy plant in your home.          Soil recipes



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