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I feel like I bang on a lot about how important it is to make sure that propagation water is really well-oxygenated, but not nearly enough about oxygenating soil.
Also, I’m not typing out the word oxygenated repeatedly, so we’re gonna go with aerated (I sometimes like to spell it aeriated so apologies in adance for that!)
Why is aerating soil important?
So, why is aeration important to soil? Same reason it’s important to us – roots need oxygen to function properly. If they can’t function properly, the plant will suffer.
There are a tonne of more glamorous root health issues that monopolise house plant advice articles.
Things like overwatering, underwatering, bacteria, and even fungus gnats get far more bandwidth than aeration, BUT if you get the soil aeration right, then it’s easier to manage those other things (and fungus gnats eating roots isn’t enough of a thing to waste any time on).
So now we’ve established why aerating soil is so important, how do we go about doing it?
Pot your plants in an airy potting mix
I always used to preach about keeping plants in a very airy, chunky potting mix. Whilst it’s the best for most indoor plants, I’m now of the opinion that you may want a slightly denser mix if you’re prone to neglecting your plant.
If you’re an overwaterer, things like orchid bark that create a lot of holes in the soil are perfect.
There are various things you can add to your soil mix to make it chunkier and therefore more oxygen rich. Perlite is great because it creates pockets of air in the soil and absorbs water. The plants have access to water for longer, but the soil isn’t sodden because the water is trapped in the perlite.
It does have a tendency to float to the top of the soil though (and get covered in algae). Neither of these things are harmful, but if you hate the way it looks (I don’t care, but plenty of people do) then consider using bark instead.
Another option is leca. Leca is usually used as a substrate when keeping plants semi-hydroponically, but it can be a great way to aerate soil too.
Repot your plants
Soil can compact over time, especially if you typically water from the top. Some plants, such as hoya and succulents, have shallow root systems, so they may not outgrow their pots, er, ever. It can be a good idea to repot them in fresh soil every so often* so that the soil and roots doesn’t consolidate into one solid mass.
*I know you’re gonna want to know how often we should do this, and the proper answer is probably ever couple of years, but I have a Hoya bella that really, really needs this, but she always seems to be about to bloom whenever I remember that she needs a repot. I’ve NEVER repotted her (I’ve added a bit of soil once, IIRC) and she is DUE. But obvs she’s full of peduncles atm and I’m not touching her. I also really want to prop her but again, peduncles.
Manually aerate the soil
Well, Caroline, why don’t you just stir up the Hoya bellas’ soil with a chopstick, I hear you ask. Trust me, we are WAY past that.
However, for those plant parents that are less negligent than I, stirring up the soil with a skewer or chopstick a couple of times a year is a great way to avoid the very situation I’m in now.
Be gentle, because there are roots down there – I sometimes use a metal skewer and then regret it when I feel a root being impaled (do as I say, not as I do!).
Yeah, I know there’s bark in there, but I just basically top dressed with that so it’s essentially just decoration. Look at her peduncles:
Hmm, I do have do a bit of repotting this afternoon…might just get her sorted. It’s literally now or never.
Use a pot that allows aeration
There are a couple of different options here. The first is a net pot, which is a pot that have holes all around, like this:
These are great BUT they don’t look great (though you can sit them in a pretty cachepot) and it can be hard to keep the soil in. The soil I use works pretty well in them, but if yours is too dense, it’ll just pour out.
Not only does the air flow through, but the medium dries out more quickly; as we know wet medium can lead to deoxygenation if it stays wet for too long.
Terracotta is the other option – it’s porous, so air can flow freely through the pot. Terracotta is a great option for plants that like to dry out quickly, like succulents, but they dry out too quickly for a lot of people. They’re fine in winter, but in summer you can end up needing to water daily. If you like the aesthetics, you can either use them as cachepots or seal them to stop them from being so porous.
This isn’t something you need to be overthinking – but do be aware that roots need access to oxygen regardless of the medium they’re in.
If your plant is growing fine and doesn’t need repotting, then leave it be. I see lots of newbies to the hobby try to do everything perfectly, and then get overwhelmed when the plants start showing signs of shock.
I have bought plants in some SHOCKING potting mixes – I had a Hoya in pure coir – and they’ve been 100% fine.
If you’re ready to repot and you’re not sure if your soil mix is airy enough, adding a bit of perlite is effective without dying out the mix too much.
Don’t worry about the ratio – anything up to 50:50 is fine. You can grow plants in pure perlite so don’t worry too much about overdoing it.