Updated: Oct 17
A Brand New Invention!
Potting mix is a pretty recent invention, first developed in the 1930s, and popularized in the 1960s. Before that, people would literally just go to the woods and dig up soil to bring home. The problem was that this kind of soil was heavy, inconsistent, and would compress over just a few months. At this time, trees and perenials (plants that can survive winter outdoors) would be grown in fields, dug up, and bagged. Annuals (tropical plants that can't survive winter outdoors) were grown in random soil from outdoors. The inconsistency was a huge problem here, since a whole season's worth of plants could die over a bad batch of soil.
To fix this, soilless potting mix was developed. It was lightweight and a lot easier to produce consistently. Yep, that's right! A lot of the time, the "soil" plants are sold in isn't actually soil. It's a mixture of peat, perlite, and fertilizer pellets. Wait- peat? Perlite? What are those?
Nice to Meet You, Peat
Peat is ancient decomposed moss. It's harvested from the bottom of bogs and taking it away isn't exactly great for the environment. It takes 1,000s of years to make, with each bog producing a layer less than a millimeter thick per year. This happens underneath the live sphagnum moss, in areas where it's really acidic and low in oxygen. This means a lot of habitat has to be disturbed to dig it up.
These habitats are mega important though, and nothing we should be messing with. Peat bogs store more carbon than all forests combined. Now is definitely not the time to be stirring things up and releasing all that carbon into the atmosphere.
Peat looks like soil, but it doesn't have any nutrition. It kinda just acts like a sponge, and after a few months, it starts to go bad, getting acidic and compressed.
More Stuff Inside!
Perlite is like volcanic popcorn. It's those weird little crunchy white pellets. Again, this doesn't have nutrients. It's supposed to aerate the soil, since roots need air pockets to prevent rotting. Vermiculite is another ingredient and is basically perlite with a different look. Instead of white crunchy pellets, vermiculite takes the form of shiny beige flakes.
Sometimes, pine bark is used, as another way of helping with airflow.
Sand is used as a cheap filler that increases weight and helps prevent plants tipping over. Sand is another ingredient with no nutrients, and since it's essentially tiny pieces of quartz, it's not very good for airflow.
Charcoal is a trendy ingredient that hogs nutrients like a jerk, stopping plants from being able to get to them. Yes, it takes out toxins, too, but, um, why are there tickets in your soil? Everything ok? Please don't feed your plants rat poison.
Pebbles are a big nope and a one-way ticket to root rot. Heavy guys with no pores! They're the worst for airflow.
But What's for Dinner?
Because a lot of "soil" isn't actually soil, the plants have to rely on fertilizer to eat. Usually, you'll see these weird little spheres in the soil. These are slow release fertilizer pellets. There's a problem with this, though. If a plant has more fertilizer than it can use, it gets burnt. That's probably one of the main causes of plants getting crispy tips and edges.
The fertilizer given to pre-potted plants is usually the right amount for a greenhouse, where the plant has more light and more humidity. These kinds of conditions allow the plant to grow faster and use more nutrients. In a house, things are a lot different, and the plant can't keep up with the nutrients being released to its roots. They get overfed!
Meanwhile, bagged soil only has a tiny bit of nutrients in it. That way, people will have to repot their plants super often, buying more and more and more.
What the Heck, Man?
Ok, so why do they use that kind of "soil" then? Good question. I don't have a definite answer but I have a few guesses. In the gardening community in general, there's a lot of information going around about keeping things sterile. It's thought that this prevents diseases, when in reality, it does the opposite.
Here, let's look at a test I did recently. I grew the smallest seeds I could find: basically dust, in my soil mix that's the opposite of sterile. Online, the advice was to thoroughly sanitize everything, but I'm a bit of a dirt rebel, a soil punk. Now, what happened?
Success! So excited to see how they grow. Fun fact: I use this soil to grow plants from leaf cuttings, too: even succulents!
Bacteria and fungi, even bugs- are so tiny, you really can't keep them all out. Sure, you can use boiling water to disinfect, but a single microscopic spore could still float its way into your soil mix. When there's no good bacteria or fungi to take up the space, the bad stuff has plenty of room to take over- easy peasy! If you've ever had your seedlings eaten by mold, you'll be all too familiar with this sort of catastrophe. Repeated disinfection, pesticides, and fungicides are seen as the easiest solution, but the second that stops, the plant is super susceptible to basically everything.
Plus, if your plants die at the end of the season, or you keep having to buy more soil mix, that actually benefits the plant companies. They want their plants to be disposable, that way they can sell more. Nobody tells you your orchid could bloom next year if you give it something good to eat, they just assume you'll throw it away and buy another one.
Let's Fix This, Like Right Away
Now, here's the good stuff, the stuff I'm kinda obsessed with: my nerdy niche. First, let me thank Gardening in Canada on YouTube. She's a soil scientist, and her videos are basically what got me into all of this. Ready now? Let's get our hands dirty!
Right, so, first: what do we do about the peat? Coconuts! Yes, coconuts. Coconut shells can be ground up into tiny fluffy pieces called coconut coir. This stuff lasts way way longer and is a heck of a lot less environmentally disastrous. It's a byproduct- finding a use for leftover "trash" from the coconut industry. Taking a fruit off a tree is way more sustainable than digging up an entire bog, especially when each tree makes 150 coconuts per year. So talented! Low-key? I'm thinking of planting a coconut. The baby plants are really silly looking.
Now that we've got the spongey fluffy stuff, what about aeration to break it up? More coconuts! No, really, I'm not joking. I straight up just use bigger chunks of the stuff. It's very porous and lightweight and creates those nice air pockets. Again, it's way more renewable, too!
Compost is Cool, I Swear
Got that, now what replaces the fertilizer? Ok, that's the really really really cool part. We've got compost! Compost is basically anything decomposed. It's what makes up the top layer of soil in a forest, and it's a really rich dark chocolate color. Compost is full of nutrients, AKA whatever the plant was made of before it decomposed. Though some of it will escape into the air, a lot of it gets held onto. It's like if a plant was a Lego set. You took it apart slowly over time, lost some of the pieces under the couch and behind the dresser, and eventually ended up with a box containing a fair amount of the bricks you started with. These bricks would be the compost, and they can be made into a plant again!
The ingredients and the way they're decomposed end up having a big impact on how the finished product turns out. You want variety, ideally. In my compost, I only use plant ingredients. Manure can be composted, but you have to be a lot more careful, since it can have stuff like e. coli. Yikes! I'll steer clear of that, thanks.
A traditional way of composting involves making a huge pile of stuff outdoors and turning it regularly with a big shovely thing. The compost breaks down by way of bacteria in the center of the pile. These bacteria participate in NSFW activities, generating lots of heat before eventually dying off when they run out of food. I don't like this method because a lot of the nutrients just escape with the rain, plus it's physically demanding to go outside and turn the pile over and over. It's also just a lot more difficult and time consuming from my experience. Not only that, but the compost loses so much more of the bulk in general, compared to worm composting. Wait, worms, huh?
It's Worm Time, Baby!
My favorite thing in the world used to be telling people I had two bins of worms under my bed. The look of confusion on their faces was priceless- and it wasn't a lie! Worm composting is super practical cause the worms do everything for you. You just have to give them a nice container with air holes and feed them a balanced diet of dead brown stuff and dead green stuff. Mainly, I use shredded paper, apple cores, banana peels, and dead leaves from pruning. With a contained bin, the nutrition can't get rained out, and you end up with a lot more reward for whatever you put in.
Ok, but it's not just about the nutrients. It gets better. So, worm compost happens at room temperature, right? It's got bacteria and fungi involved, too. I've built up a pretty diverse culture in my worm bins over time by adding ingredients from different sources. (God, I want a fancy microscope so badly.) The bacteria and fungi are cool because they're the friendly kind. If you keep a good pH in your bin and good airflow, you'll end up with these types of microscopic things that can protect the roots of your plants and extend their reach, creating a web throughout the soil. The roots communicate with this stuff, the mycellium, by sending out specific sugars that attract specific fungi. Those specific fungi eat the sugar and at the same time, release enzymes to turn compost nutrients into a liquid the plants can drink, right in the root zone! This way, plants order the specific foods they want. It's amazing!
You might see some other bugs, too. Don't worry. Soil bugs like these aren't here to hurt. They're bodyguards! Not only do they help out more in the dissolving of nutrients, but they keep things clean in terrariums, preventing any visible mold. They literally eat mold so fast, it can't hurt your plants. What else do they eat? Rude bugs. Soil mites and isopods will literally eat spider mites and other rude bugs, protecting your plant and making it harder for infestations to happen!
But wait, there's more! With worm compost specifically, there's a special kind of compound in it that plants can absorb, and it's literally poisonous to some of those evil bugs. They're phenols of some sort, but that's- big science stuff, let's chill out a little.
What else is in there? Rooting hormones, naturally occurring, stuff that encourages growth by sending signals to the plants like "Hey, more leaves and roots, please!"
Compost reduces the need for pesticides and fungicides, and it makes fertilizer pretty much irrelevant. Plants can't get overfed if they're ordering their own meals. They pace themselves and grow with just the right amount, no burning! With compost, you want it as 40% of the soil as a maximum. I find that this is overkill. You'll see a bit of extra nutrients as a white crust on the soil, and it's just not a cute look. My soil mix has compost as less than a third, since that's what's been working best.
Wait so what happens to all the good bacteria even you use pesticides and stuff? Sometimes you can wipe it out, but sometimes it can just bounce back. Try to avoid getting too much of it in the soil, but if you have to, you can add worm castings to the soil to reintroduce the good guys later.
God, I could go on about this forever. I haven't even mentioned water retention yet. Let's save that for another article, ok?
Rounding it Out
For the second to final touch, I'll talk about my last two ingredients in the soil I use and sell in the shop: mosquito bits and akadama. Mosquito bits are infused with good bacteria. They're non-toxic and all they care about is killing fly larvae. When soil contains mosquito bits, fungus gnats can't make babies in it.
Akadama is something that's usually used in bonsai. They're special orange clay pellets from Japan: a mix of rock and mineral particles with composty particles. They're very porous too. So, basically, this stuff's good at holding onto nutrients from other sources, kinda like a battery, but I mainly use it for another reason. It changes color really dramatically when it's wet or dry. That way, it gets a lot easier to tell when your plants need water. It makes this really dramatic hissing sound when you water it too- very satisfying.
So everything comes together now, right? All measured and mixed. It lasts and lasts, with so much nutrients that your plants can just go off of for months, or even years, depending on the type. Over time, algae shows up, with the power to add air into the soil and nitrogen as well. Algae, fungi, bacteria, roots, they all hold the soil together with sugars, stopping it from all spilling out. Tiny bugs weave pathways for roots to follow. Your plant has a kitchen, a team of bodyguards, personal chefs, ingredients. You might wonder why soil isn't always like this.
The Future of Dirt (so exciting?)
It comes down to tradition and convenience. People are used to things being a certain way. If the companies went through all the work involved in changing things, there'd be issues. People want what they've always had, what they've learned to work with. They don't want to have to figure out something new out of nowhere. The concepts about soil and soilless mixes, about disinfecting with boiling water, these are widespread rumors that people live by. Still, maybe it's time to experiment and grow. It was a relief for me, not having to go through the whole "don't breathe on anything" process, planting tiny seeds in living soil instead of the disinfected kind. Maybe, if this new way is truly easier, it'll spread over time: the next big dirt. Who knows?