The Story is in the Soil.
It really is everything. Knowing which potting mix your plants need can be the key to a happy plant. There are many options in soil (or soilless) mixes, and they all have a purpose. Here we’ll cover what you need to know.
What is Soil?
Most people think of soil as the stuff that comes directly from the ground outside. It’s like potting mix that nature made. It’s full of decomposing plants, animals and insects which release nutrients and minerals into the ground and make it fertile, or at least that’s the hope. Many of us have heard about our crops being devoid of minerals such as magnesium due to farming the same fields repeatedly, denying the soil a chance to replenish. Soil is also full of billions of beneficial bacteria and fungi that help to break down the decomposing plant and animal matter. This crazy ecosystem within the soil - bacteria, fungi, insects and more - is truly living. It’s an amazing system in perpetual motion, even when we can’t see it happening. Even more fascinating, this ecosystem changes depending on the area in which you live. Here in the U.S., our conditions can range from light and sandy to marshy all the way to dense clay. Choosing outdoor plants that are native to your area can help support your soil and your outdoor garden.
Any part of this ecosystem that gets separated from the whole - say you work in your yard and come inside covered in dried mud - this is dirt. It was once part of the whole, but it became disconnected and no longer lives and breathes with the system.
But we’re here to talk about indoor plants, which are usually far from native in most cases. That’s one reason why they’re in our homes. Our lofty goal is to recreate these soil-like (whatever’s relative - we’re looking at you, epiphytes…) conditions for our indoor plants.
So, what is soilless mix and why do we want it? Soilless mix is usually peat based rather than soil or topsoil (outside stuff) based. It’s loose, airy, light, and sterile. We want it because it provides a clean, fresh environment where a plant’s roots can move freely. It’s less likely, depending on the composition, to turn into a muddy mess and it doesn’t usually compact unless it’s very old or some overzealous potting practices were used. Soilless mix is a good thing. It’s good for you, your plant, and your home. Peat, though, it has pros and its cons. Peat is actually Sphagnum peat moss, and it’s become quite controversial due to how entirely not sustainable it is unless careful measures are taken. There are some companies out there practicing careful and sustainable farming, which we’ll discuss below. There’s also the alternative of using coconut coir instead of peat. Coconut coir is more sustainable while still being breathable and sterile, which are potting mix necessities.
Soilless mix alone isn’t enough to keep our plants happy and thriving. Sure, it’s light and comfy for the roots of our plants, it’s free of weeds and undesirable insects, it’s more accommodating to tropical or subtropical plants than the soil outside our door, but it needs more. This is where amendments come in, and the fun begins. Amendments are where we can truly customize our mix to each plant, giving our little guys and gals the best chances of survival and happiness. This is also where we can customize our mix for our needs. Tend to overwater? Make that mix even faster draining so your plant will dry out before you forget that you already watered it this week. No, it isn’t a miracle, but it helps those of us who might have so many plants (guilty!)that we get a little forgetful. So what are some examples of amendments? Perlite, bark, charcoal, and coir can be used as amendments.
Below you will find some tried and true soilless mixes, amendments, and some suggestions on how to use them.
A sad note: I would love to include a potting mix here that I purchase locally, but unfortunately they only offer their mix in-store. With that in mind, I still wanted to give my local nursery the shout-out it deserves.
General Potting Mix.
For Most Common Houseplant Varieties, All-Purpose Potting Mix.
This mix is great for most common houseplants. Spider Plants, Prayer Plants (Maranta), or hanging plants like Pothos that might be more difficult to water frequently will enjoy this recipe. This mix will satisfy their thirst while still being fast draining enough to keep the roots from rot. Two parts of your base mix (Espoma Organic Potting mix) plus one part Perlite and one part Earthworm castings should do the trick for most common houseplants. You can always add more perlite if the soil seems overly heavy or if you don’t trust yourself to water conservatively.
Espoma Organic Potting Mix.
This is a great base for your general, all-purpose potting mix. It’s organic, it supports healthy roots, and it isn’t loaded with synthetic fertilizers. I love that it allows me to choose my fertilizer rather than being tied into 6-12 months of “built in” fertilizer. However, if you love the “built in” option, just sub that potting mix for this one and move on to the next ingredient!
Espoma Organic Perlite.
This one is crucial. Perlite is an amendment that is added to your base to make the soil lighter and more airy. It looks like little styrofoam puffs, but it’s actually a type of volcanic rock. Perlite makes the soil more oxygen friendly. It’s critical that your plants roots have access to oxygen. Without it, heavy soil + water = root rot. A long drying time creates the perfect conditions for root rot to take over. Perlite helps regulate that, so we don’t have soil that’s wet for longer than our plants need to absorb the water and get back to breathing oxygen. Don’t skip out on this step.
Wiggle Worm Soil Builder -Pure Earthworm Castings.
These add a natural, healthy boost to your potting mix in a language that your plant speaks fluently. Remember from above how soil is a living and breathing thing? These earthworm castings would likely be a part of that system. They are an amendment to the mix, but we also discuss how they help as a fertilizer here.
Epiphytic Potting Mix.
Hoya, Orchids, Jungle Cacti, and Many Aroids.
I mix this in my kitchen, and it’s my most used mix. I use the same ingredients when I mix for Aroids, Orchids, Jungle Cacti, and Hoya, but I change-up the ratios depending on each plant. Typically, I use equal parts of the first two ingredients, while using less of the earthworm castings. For every two scoops of general potting mix, I use a half a scoop to a full scoop of castings.
Certain Hoya or Orchids need a chunkier mix. In that case, I would use more Orchid Mix and less of the “base” mix, Espoma Organic Potting Mix. The ratios change depending on the plant I need to pot. Some of my Hoya plants like a chunkier blend which allows for more air flow to the roots and typically allows for the space around the roots to dry more easily. I use more of the Special Orchid Mix for these plants. Other plants might not typically require a chunkier mix, but the environment calls for it. My Hoya lacunosa next to the shower is an example of this. My four other lacunosas are in equally measured mix, but the one in the bathroom lives in a very moist environment. The surface of the soil becomes visibly moist more than once per day as the shower is turned off and on. If not for a chunky mix, this plant could become overly wet, causing damage to the roots.
Most of the aforementioned plants have similar soil needs because they are all epiphytes. This means that they live on a host rather than terrestrially or in the ground. There are many other houseplants that are epiphytes, including some ferns. To hear more about Epiphytes, you can visit the Rhipsalis page, where there’s more detail in the intro.
Espoma Organic Potting Mix.
This is the jumping off point to which the amendments will be added. This is what we might call a base to our potting mix. Fortunately, this mix already has added earthworm castings and kelp meal, among other treats, that plants adore. Remember hearing about sustainability? Espoma has made some very impressive commitments to the environment, and as if that isn’t enough, the product is good. And to further customize your soil, they offer a variety of organic mixes to serve as your base, including a Moisture Mix, a Seed Starter, and more.
Better Gro Special Orchid Mix.
This is a real lifesaver. Sometimes you’re feeling crafty and don’t mind mixing up a batch of potting mix from scratch, and sometimes you just want somebody to be smart for you. Better Gro was smart for all of us and made this awesome Orchid mix that blends so nicely with the basic potting mix of your choice. It has Fir Bark, Charcoal, and lovely chunky Perlite to give Epiphytic roots all the air flow they crave. Don’t fret about the name, this mix is amazing for Hoya, Aroids, and Jungle Cacti.
Wiggle Worm Soil Builder -Pure Earthworm Castings.
I admit to going a little nuts with earthworm castings. I add more. I think it makes my plants happier. I look for earthworm castings that specifically mention houseplants on the bag. I have used a few different types, including this Wiggle Worm Soil Builder, and have felt satisfied with the results.
A Note About Begonia Potting Mix.
In an odd turn, I find that a version of the above Epiphyte soil with less of the Special Orchid Potting Mix is great for Begonias. They don’t fit the profile for this soil, but like Epiphytes, they hate to have wet feet or sit too long in water. Since they like to dry out between waterings, this airy soil helps keep their roots fresh and rot-free. Try two parts Organic Potting Mix, one part Special Orchid Potting Mix, and one part Wiggle Worm. Begonias especially appreciate the earthworm castings. Castings are full of Nitrogen, and Begonias love to feed. See here to learn more about them.
Cactus and African Violet Mixes.
Espoma Cactus Mix.
I love my desert cacti too, not just my jungle cacti. I also have a precious Aloe plant that I want to spoil and nurture. These plants can’t tolerate the chunkiness of the Epiphytic soil, and the General Purpose soil is too heavy for them. It’s just not how they’re used to growing. The key is mimicking the natural conditions, so for cacti, we need a Cactus mix. I like to add a handful or two of grit that I buy locally. It’s more dense than sand, but less substantial than small pebbles.
Espoma African Violet Mix.
This is not just great for African violets. It’s also great for Columnea, otherwise known as the goldfish plant. African violets are a craze, and I’m into it. This African violet mix is especially well draining, without the grit of a Cactus Mix or the chunkiness of the Epiphyte Mix.
Mixing and Other Odds & Ends.
Blending an Epiphyte mix requires some scooping and some digging, but it’s worth it. Your plants will certainly think it’s worth it. You can use any method under the sun to mix. I like to use my bowl, cup, and a pair of spoons.
IKEA TRYGG Serving Bowl, $2.49 - no longer sold in stores, but I continue to use mine.
IKEA DINERA Mug, $1.99
I blend with two spoons, kind of like tossing a salad.
FYI:
When you first begin mixing your own soil, there’s a transitional period in which you’ll be learning how to water for your new soil. This is good. There will be some trial and error, but it’s all about giving your plant what it needs.
Some other general info about potting mix:
-Be sure to close and seal all bags of potting mix after each use. Pesky gnats or similar creatures love to make a home in those juicy bags of mix.
-Cover your mixing bowl if you have leftovers after potting.
-Store mix in a dry spot.
-More is not better when it comes to potting mix unless you’re dealing with a root-bound plant. Pot up 1-2 inches as a general rule. Potting up more than 1-2 sizes could result in root rot. It’s tempting to believe that a bigger pot will create bigger plant, but it’s likely to cause a stressed plant. Your plant is likely to focus on growing in roots before foliage, all while sitting in a pot that takes longer to dry out.
-You don’t need to remove every single solitary morsel of old potting mix from the rootball when you repot. It’s okay, even safer, for your plants if you don’t pry deeply into the roots. The purpose of soil or potting mix is to help the roots do what they naturally do. They can’t do that if they’ve been over-handled or traumatized. Just gently shake loose whatever falls freely and replace the rest with your new, fresh mix.
-If you tend to overwater, use a chunky mix with a terra-cotta pot. Both allow oxygen to move through the roots freely, and you’re less likely to drown your plant.
-Check your potting mix of choice and take note of any slow-release fertilizers. Be careful not to use additional fertilizer if you’ve chosen a potting mix containing fertilizer. You can read more about fertilizers here.
-Check for proper drainage in your pot of choice. There’s no sense in creating a perfect custom mix if it can’t drain freely.
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