The potting mix indoor gardeners use to sustain houseplants can help or hinder their plants. This is typically because what is contained within those potting mixes dramatically changes how quickly water passes through the potting medium. A dense potting medium will stay wet for longer periods of time than a well-draining mixture.
Understanding what a dense potting mix looks like or is typically composed of versus a well-draining mixture can empower you to make a decision about what kind of potting medium you want to pot your plants in.
Many of the houseplants we keep prefer well-draining mixes. Additionally, many of us are recovering overwaterers, which means that we can also benefit from well-draining mixes that help to minimize the effects of providing our plants with too much water,
This post will go through some of the ways we can identify what kind of potting mix we are looking at in the store AND what we can buy to add to those mixes to increase the drainage for the health of our plants.
Should you buy pre-made potting mixes?
If you are like me, you’ve bought the bags labeled, “Indoor Potting Mix” many times with the assumption that these mixes are perfectly designed to help your indoor plants thrive.
However, many of these potting mixes have components designed to retain water rather than drain water.
Some will contain moisture crystals that absorb water so you have to water your plants less. Avoid these mixtures! They increase the chances of you unintentionally overwatering your plants because the potting medium stays wet for far too long.
Others may contain very few components designed to aerate the potting mix and, therefore, increase drainage (such as perlite, orchid bark, and others that we will discuss later in the post).
Some pre-made mixes also contain chemical fertilizers. Depending on the strength of these fertilizers and what your normal fertilization practices are, this may work for you.
However, overfertilization can damage plants, so just be aware of whether the mix you choose includes fertilizer. I specifically choose mixes that do not so I control the amount of fertilization my plants receive.
Can you still buy pre-made potting mixes?
Yes! My recommendation is to use a premade potting mix as a base and add additional ingredients to help provide more drainage.
Is there an option that can be bought as-is and not hand-mixed?
Yes! My recommendation for people who want a well-draining, pre-made mix to buy a cactus potting mix.
Because these mixes are designed specifically for cacti and succulents that need very little water, these products will already have various substrates to increase aeration and drainage. This means that you could use a cactus mix with many of your houseplants without needing to add anything else.
This is the strategy I used for a while before I was ready to mix my own soil and it worked well. I now like to add more perlite and bark than would be in a pre-made cactus mix, but I have kept many plants alive and happy with cactus potting mixes!
My preferred cactus mix is Espoma’s Organic Cactus Mix (linked to Amazon through the Affiliate Program).
What kind of potting mix should you start with?
I recommend any organic potting mix of your choice.
Organic potting mixes have natural fertilizer sources (such as worm castings) rather than chemical fertilizers. Organic fertilizer sources are much less likely to burn or damage your plants.
Also, the organic potting mixes, in my experience, have never included moisture crystals or other unnatural/inorganic substances used to retain water.
What do you add to a potting mix to increase drainage?
Some examples of items that can increase drainage are perlite, vermiculite, orchid bark, and pumice.
Perlite is puffed volcanic glass, which adds a light airy texture to the mix. It is very similar in texture to styrofoam balls.
Orchid bark is large and chunky bark pieces that provide spaces for air and root growth. It is particularly great for epiphytic plants (plants that grow and climb on trees/rocks/plants). I have a bunch of these like hoyas, pothos, and philodendrons.
Many people may choose to only add one of these ingredients. The most common is perlite.
My personal potting mix recipe:
When I mix my own soil, I use a combination of potting mix, perlite, and orchid bark for most of the plants in my home. An approximation of what I use is 60% potting mix, 20% perlite, and 20% orchid bark.
For cacti and other desert species, I use 50% potting mix, 25% perlite, and 25% sand.
It is definitely not an exact measurement. I pour each ingredient into a bucket and until I feel satisfied that the mix appears airy and diverse.
Should you match the plant species with the potting mix?
What potting mix you use can be determined by what plant you have. I deliberately leave this section a bit open-ended, though, because there is a lot of personal preference involved in potting mix choice including whether you want to alter the ingredients of your potting mix based on the species of plant you are caring for.
For example, while most plants like well-draining mix, there are some that prefer to have some level of moisture at all times. For these plants, you could consider a denser potting medium.
Some examples of plants that like to have a level of moisture at all times are calatheas, marantas, and oxalis.
I personally choose to use an equally well-draining mix for the plants that like to maintain some level of moisture and water them more frequently. This is the choice I have made because, while these plants are more moisture friendly, they are capable of developing root rot and I don’t want to risk it.
I do alter my potting mix in one instance, however. I do not include orchid bark when I’m potting up my cacti, euphorbia, and succulents. They do not benefit as much from orchid bark as my epiphytic plants do.
Instead, I add more perlite and some sand to increase drainage.
The only exception I can think of is my Schlumbergera, or holiday cactus, that is an epiphytic cactus! That one did get some orchid bark!
The vast majority of plants will do great in well-draining potting mixes because they prefer to dry out completely between watering. Some common examples are pothos, zz plants, snake plants, dracaenas, hoyas, cacti, succulents, philodendrons, spider plants, and string of hearts.
It is easiest, if in doubt, to do a little research on the plant you are purchasing to have a better understanding of what the recommended substrate and care is.
Should you add charcoal to your potting mix?
Horticultural charcoal is definitely an item worth considering! When added to potting mix, it will guard against insects and mold, absorb odors and excess water, and help to control impurities in the potting mix!
This becomes especially important when setting up terrariums and vivariums (enclosures that often maintain high humidity for plants and sometimes inhabit reptiles or amphibians as well).
Enclosed systems mean less airflow and higher humidity which increases the potential for mold, fungus growth, and less-than-pleasant odors. The addition of charcoal can help to decrease this potential.
Should you top-dress your potting mixes?
Top-dressing your potting mixes can be helpful in maintaining moisture and pest control.
Pebbles can help to maintain moisture for plants who prefer some level of moisture most of the time. I use these on top of my calatheas and marantas, for example.
Pumice can be a great way to discourage fungus gnats from reproducing. Fungus gnats have to dig into the potting mix to lay eggs or dig out of the mix to fly around. With pumice stones on top of the potting mix, they would need to scrape their bodies against the stones to get into or out of the mix, which they do not like. It’s a win-win!
Another way to discourage fungus gnats is to add sand to the top of your potting mix, which can look quite nice but may need to be a bit groomed over time.
- Potting mix should be something that works for you and your style of plant parenthood.
- Well-draining mixes are best-practice and are most recommended by houseplant experts.
- To make a mix more well-draining, you can add perlite, orchid bark, or other soil amendments
- To buy a pre-made mix that does not require adjustments, try a cactus mix.
- Be wary of mixes that include chemical fertilizers or moisture crystals.
- Most importantly, observe your plants and see how they respond to your potting mix choices. Then adjust if needed.
Good luck! share any of your questions, tips, or tricks below!