When you read about plant care online, you’ll frequently come across discussions about proper lighting, watering strategies, or propagation techniques. But one essential component of your plant’s health and happiness is potting medium. While many of us have probably reached for an all-purpose potting soil to care for our little green friends, in this article we’ll discuss some incredible alternatives to soil that can improve the health of all of your plants.
First off, what’s wrong with soil? Don’t plants and soil go together all the time? Isn’t that kind of their thing? Well, yes! In nature, where the soil is being constantly tilled by earthworms, insects, and weather, and revitalized with minerals from rain and natural compost, plants thrive. But very rarely do our home environments mirror nature’s biodiversity.
What often happens, instead, is our indoor potting soil begins to compact over time. As it does, the soil loses its drainage qualities and stops providing oxygen to your plant’s roots. The harder the soil compacts, the harder your plant’s roots will have to work to penetrate it. The more energy they expend putting out roots, the more their growth is slowed, meaning that the overall health of your plant will deteriorate, while being more susceptible to disease, pests, or root rot.
There are lots of ways to counteract this compaction, from additives that will aerate the soil, to refreshing the soil every-so-often. But today we’re going to instead provide you with all the information you need to start your journey into non-soil potting mediums.
Potting Mixes vs Potting Soils
It may come as a surprise to the novice plant-grower (it did to me), but there’s a big difference between potting soils and potting mixes—namely, what else goes into the mix. While we will talk briefly about how to blend your own all-purpose potting soil, with helpful additives to provide benefits to your plant, we’ll be focusing mostly on potting mediums that require no soil.
Potting mixes are designed to resist compacting by staying loose and lightweight, ensuring that your plant’s roots have continual oxygen access. They also help you achieve the challenging goal of having proper drainage and healthy water retention. How do they manage all this? With the help of amendments.
Amendments: What They’re For
Amendments are organic or non-organic additives that you can introduce to your potting medium to help achieve that sought-after balance of water, oxygen, and nutrition. Fertilizer is an example of an amendment you’re already likely familiar with, but it’s not the only one. Here are some other amendments that you will likely find in non-soil potting mixes, alongside the benefits that they’ll bring with them.
Bark:
Bark is a good way to break up your soil and provide aeration, specifically with mature plants that need to dry out between waterings. It isn’t ideal or necessary for your tender plants, or if you’re growing from seeds. Many kinds of orchid prefer a potting mix that is just bark and sphagnum moss.
Sand:
Sand is a common ingredient in potting mixes both for adding drainage, and resisting compaction. Mixes designed for cactus, succulents, or rosemary, are often one-third sand.
Coir:
Peat Moss, or Sphagnum Moss, has been a long-time favorite amendment of all kinds of potting mixes. But rather than discussing Peat Moss, I opted to use Coir instead. Coir (pronounced Coy-er) is a fiber that comes from the husks of coconuts, and which is gradually becoming a more sustainable substitute for peat. Most likely you’ve encountered Coir as the scruffy, brown liner in a hanging flower basket or a spongey doormat. A little-used byproduct of the coconut industry, Coir is rot-resistant, water-retentive, and sterile—meaning it won’t introduce any pests or disease into your mix. It’s also pH neutral, unlike Peat Moss, which can be more acidic, and require additives like limestone for balance.
It’s also significantly more sustainable than its more commonplace counterpart. Peat can take hundreds of years to form in the wild, and even when it is harvested with an eye for sustainability, it’s challenging for producers to keep up with an ever-growing demand. By shifting our consumption to Coir, we can decrease our dependence on peat, and still have an ideal additive for our potting mixes.
Perlite:
Another common amendment is Perlite, the tiny white pebbles that float around in many different potting mediums. While Perlite may look like flecks of styrofoam, Perlite is actually a volcanic mineral that provides your potting mix with both drainage and water retention. Its light weight and porous surface help keep your mix aerated, which avoids compaction and maintains consistent water access. For a succulent or cactus mix, using more Perlite than Vermiculite will help maintain a drier, more airy soil.
Vermiculite:
You’ll often see Vermiculite and Perlite paired in the same mix, but they’re actually two different amendments. Vermiculite has a less symmetrical, gray appearance, and is a naturally occurring mica: a soft, lightweight silicate mineral that is which sterilizes the material and causes it to expand, creating a texture and shape perfectly suited to retaining water and oxygen. If you’re dealing with plants that tend to dry out quickly, you can add more Vermiculite than Perlite to your mix and increase the water retention. Also, like Perlite, Vermiculite is pH neutral and won’t affect the acidity of your potting mix.
Activated Charcoal:
At this point, what can’t you use activated charcoal for? This versatile carbon residue is a great way to keep your plants pest and disease-free. Additionally, its incredibly porous structure soaks up water like a sponge, which can come in handy if you have a tendency to over-water.
Compost:
While compost is an excellent way to introduce nutrients to your plants by recycling decomposing organic matter, it’s more commonly found in outdoor gardening, and only appears in our all-purpose potting mix. For that reason, we won’t spend much time on it here.
Hydroculture:
While we go more in-depth on Hydroculture and Hydroponics in articles like LECA: Going Semi-Hydro and Hydroponic Houseplants: How to Grow Plants in Water, it’s still worth a mention here. In Hydroculture, plants are allowed to grow in soil until they’ve formed roots, and then they are removed from the soil and transitioned to a growing medium known as LECA.
LECA, which stands for “Lightweight Expanded Clay Aggregate,” is a clay based potting mix that, in addition to looking like Coco Puffs, also doesn’t break down over time, and has capillary properties that wick water upwards towards your plant’s roots. This technique, sometimes referred to as Semi-Hydro, involves a constant level of shallow water in your growing container, which the LECA draws up to oxygenate and hydrate your plants. The benefits to this include an absence of fungus gnats and a watering system that excludes any guesswork, leading to plants with longer lifespans. Click on the links above to learn more about Hydroculture.
Making Your Own Potting Mixes
Now that we’ve discussed some of the more common amendments, we’ve included some recipes for how you can mix your own soil! You’ll see that we’ve included fertilizer in a couple of these recipes, as most potting mixes and soils alike will tap out of nutrients pretty quickly, and will need to be replenished. We recommend looking into your specific plant’s needs before choosing the right fertilizer for you.
All-purpose Potting Mix:
3 Parts Coir
2 Parts Perlite
3 Parts Compost
+Fertilizer, proportionate to the size of your mix
Simple Soilless Potting Mix:
2 Parts Coir
1 Part Perlite
.5 Part Vermiculite
+Sand, Fertilizer depending on your needs
African Violet Mix:
2 Parts Coir
1 Part Vermiculite
1 Part Perlite
Cactus/Succulent Soil Mix:
3 Parts Coir
2 Parts coarse sand
1 Part Perlite
1 Part Vermiculite
Orchid potting mix:
6 Parts Bark
1.5 Parts Coir
1 Part Perlite
1 Part Charcoal
Aroid Potting Mix:
2 Parts Coir
2 Parts Bark
1.5 Parts Perlite
1.5 Parts Charcoal
Like any good recipe, once you learn the basics of making your own potting mixes, you’ll be able to customize them to fit your plant’s specific needs. This is an invaluable tool in your plant-care repertoire, and we can’t wait to see what you do with it!
Jeff Miller @jeffmillr
Portland, ORJeff Miller is a writer and novelist based out of Portland, OR. When he’s not taking care of his own collection of green friends, Jeff can be found writing books, short stories, and poems and curating www.thetruthaboutgoats.com, an online community for artists and creators. You can read more of his work there, or follow him on instagram @jeffmillr.
