You’re torn on what to use for your houseplants: potting soil or potting mix. To you, these both kind of look the same, so you figure it doesn’t matter either way. Is that right, or does your indoor plant favor one over the other? This might just be the cause of some of your long standing houseplant issues but had no idea what was causing them.
Should I use potting soil or potting mix for my houseplants? While it’s not true for every houseplant, potting mix is generally the better option. This contains a growth medium such as fine bark, vermiculite, perlite, and/or peat moss. Air and water can easily travel and drain, allowing the roots to develop and the plant to grow healthy.
Still a little confused about what potting mix and potting soil are? That’s okay. In this article, we’ll clearly lay out the differences between the two. We’ll also tell you which to use for your houseplants and why.
Let’s get started.
What Is Potting Soil? What about Potting Mix?
As you might recall, we just wrote a post discussing the differences between plant food and fertilizer. Those are two things some gardeners think are interchangeable (even though they’re not). In the case of potting soil and potting mix, they are somewhat more interchangeable, although not exactly.
We’ll talk about that more in the next section. For now, I want to be clear you know what potting soil and potting mix are, since they’re not the same.
First, let’s define potting soil. As you can tell by the name, potting soil is mostly soil-based. In other words, it’s dirt. Some manufacturers will add other ingredients to the potting soil, but not always.
The minerals and decaying organic matter in potting soil means it’s rife with the nutrients your houseplant needs for growth and survival. The downsides of potting soil come when you put it in a pot. Water can get trapped in there, soaking the soil. If the roots become oversaturated, your houseplant risks developing root rot or even dying.
Worse yet, if the soil becomes compacted, then oxygen has no room to travel. As I’ve written about before in 9 signs you’re overwatering your houseplants, people often “water their plants to death” by adding too much water and not enough oxygen and their plants actually “drown.”
Potting soil has a long shelf life, never becoming unstable with time. You can add manure or fertilizer to it to replenish lost nutrients, making it last even longer. Also, you won’t spend a lot of money on potting soil compared to potting mix. However, you can’t ignore that potting soil lacks aeration, it’s not very fluffy, and it can waterlog your houseplant to death.
Potting soil is not recommended for planting seeds. Why? The toughness and density of potting soil can hinder germination or seed growth.
Next, we’ve got potting mix. Admittedly, I can see where the confusion between this and potting soil comes from. If you took a handful of potting soil and put it next to a handful of potting mix, you can’t really tell the difference, at least not visually. Trust me though, there are differences.
For one, potting mix doesn’t include soil. Instead, as we said in the intro, it’s packed with fine bark, vermiculite, perlite, and/or peat moss. Each of these ingredients serves a specific purpose.
For instance, vermiculite and perlite allow the potting mix to drain. They also maintain moisture and nutrients. Peat moss retains water, but not excessively.
The media used in potting mix outsizes soil so air can travel freely. They also make for an overall softer, fluffier potting mix than what you’d find in potting soil. Since the potting mix is softer, it doesn’t weigh as much, either. That can aide your indoor plant as its roots seek somewhere to settle.
As great as potting mix sounds, it does have a few issues. For one, it lacks the near infinite shelf life of potting soil. The media in the potting mix, especially the organic ones, doesn’t last forever. With time, you’ll have to replace your plant’s potting mix to keep it growing. Also, as we mentioned, potting mix is more expensive.
Here’s a fun fact: while potting soil isn’t potting mix, you can make potting mix into potting soil. You just need a little bit of dirt.
Which Should You Use for Your Houseplants and Why?
While potting mix sounds like the better option of the two, that doesn’t mean you should use it exclusively for all your houseplants.
If you’re growing a plant in a container for instance, then potting soil is actually your better bet.
If you have a plant with specific aeration and drainage requirements or you’re growing a houseplant from seed, then you should lean more towards potting mix. This has the right texture your growing plant needs.
For the rest of this section, we’re going to tell you whether your favorite indoor plants require potting soil or potting mix. The results may surprise you!
- Philodendrons: If you’re growing beautiful, tropical-looking philodendrons at home, the plant needs soil with organic matter that drains well. In other words, use potting mix.
- Peace lily: The same goes for peace lilies and their lovely white flower. The medium must be loose, organic, and retain moisture well, aka potting mix.
- Snake plants: The Sansevieria or snake plant can develop root rot easier than some other indoor plants, so it does better with a potting mix that has no soil. This way, water can drain.
- Boston ivy: Although it doesn’t look like the other plants we’ve discussed so far, Boston ivy also favors potting mix. You want to make sure the mix has peat moss and/or perlite in it. If you want, you can use cactus mix (keep reading to learn more about this!) for your Boston ivy as well.
- Aloe vera: Speaking of cactus mix, since it’s a succulent, aloe vera grows well in this mix, too. If you’re torn between using potting soil or potting mix for aloe vera, there’s no need to choose. Either works. If you do opt for potting mix, then make sure it contains perlite, granite grit, or sand. You can even combine potting mix and potting soil if you feel so inclined.
- Pothos: Since you plant your pothos in a container to see those long vines dangle, you’d think you’d need potting soil, right? In this case, you don’t. Instead, you want a soilless mix that has plenty of peat in it. This should drain well.
- Lucky bamboo: Since it’s not a true bamboo, lucky bamboo has different growing requirements than you might have expected. For instance, you can use potting soil on this houseplant. You do want to make sure you buy a rich soil with draining capabilities.
- Gardenia: The appealing gardenia is yet another indoor plant that grows in potting soil, not potting mix. The soil should not retain water, nor should it have clay in it, but organic matter is fine. Shop around for a potting soil that drains well and doesn’t weigh too much and your gardenia will be happy.
- Spider plant: No matter which type of soil you choose, just make sure the spider plant doesn’t spend too much time in saturated soil. Another important thing is to cover the roots adequately with your mix or soil.
- Jade plant: Succulent-based potting mixes suit the jade plant best. You’re free to make your own potting mix as well if you’re up to the challenge. This should contain sand (three parts), organic matter (one part), and peat moss (one part).
- Sword fern: We couldn’t go without talking about a fern. Most of them, including the sword fern, like potting mix. The mix does require a rather unexpected ingredient: sand! This creates spacious pockets of air within the mix. Triple-check that you don’t get sand that’s too fine, as the mix won’t drain so well anymore.
What is cactus mix?
A few of the indoor plants on the list above grow best in cactus mix, but what exactly is this? It’s a type of potting soil formulated just for cacti. The ingredients prevent excess moisture from lingering around the plant’s stems and roots. Cactus mix can also maintain growing roots, so your cactus grows big, tall, and beautiful.
Can you use outdoor potting soil for indoor plants?
You may have started an outdoor garden before moving to an indoor one. You have an overabundance of outdoor potting soil left over, and now you’re thinking about using this soil for your indoor plants. After all, soil is soil, right?
Not really. Outdoor soil tends to be a lot weightier than indoor soil. It must be resistant to wind and other environmental changes, so it needs that heft. As you know, indoor soil already doesn’t drain spectacularly well. If you add an even heavier soil to your indoor plant, it likely won’t survive.
Is potting mix dangerous?
It may seem like a silly thing to wonder whether potting mix is dangerous, but it actually can be.
This 2019 article from CNN Health mentions that people have developed Legionnaires’ disease from potting mix. Some have even died.
How does that happen? It’s the fungi and bacteria in the mix. It can trigger Legionnaires’, a type of lung infection, and even other possibly fatal diseases.
Does this mean you should never use potting mix? No, not at all. CNN Health even says “the risk of becoming infected with any of these bacterial or fungal diseases is very low.”
You should wear a mask when using a lot of potting mix for an extended period of time or when working in poorly ventilated rooms or areas. I always do my best to wear a mask when I’m working up close to potting mix so I don’t breathe in any possible bacteria.
Use gloves as well to keep the fungi and bacteria off your skin. Also, always wash your hands after working with indoor plants grown in a potting mix. Yes, even if you wear gloves.