When we think about soil and potted plants, the conversation usually turns to water rather than air. Believe it or not, water is only part of what’s going on in your dirt. You have to think about how much air is down there as well.
Roots are designed to absorb water for the plant but they still need access to air in order to be healthy. Since the plant doesn’t have lungs, the only way for its cells to get oxygen is to absorb it from the surroundings.
Even though they are underground, that includes the roots. This is why most plants will do very poorly in heavy, clay-based soils.
Basically, you can smother your roots if there isn’t enough air pockets in the soil, regardless of how carefully you water.
In nature, soil is kept well aerated by all the various worms and burrowing insects that are living below the surface. For your houseplants, you won’t have these natural helpers working for you, leaving soil maintenance and aeration up to you.
Signs of an Aeration Problem
First of all, how can you tell you have an aeration problem with your potted plants? When the roots are struggling for air, you will have the same symptoms as you would when your houseplants have had too much water.
Your plant will start to wilt and leaves will show some yellowing. Of course, make sure you are not actually over-watering as well.
Aerate with Natural Materials
The easiest way to keep potted plants aerated is to add materials to their soil that help create air spaces.
- Shredded bark
- Sphagnum moss
- Coconut fiber
- Fine gravel
You may be questioning the last two items on our list. The fact is that both vermiculite and perlite are natural materials, even though they sound synthetic. Perlite is easily mistaken for little balls of white styrofoam.
Both of them are varieties of expanded minerals, meaning they are made from exposing substances like mica to high heat until it “pops.” This creates a very porous and light compound to loosen up your usual mix of soil.
It’s not artificial, and it’s safe if these materials end up in your outside soil too.
Sometimes even the best potting soil mixtures can get packed down, losing their aeration qualities by getting compacted. Every time you water a plant, the soil settles down a little more.
Without any natural disturbances to mix things up (like the worms we mentioned earlier), the soil just stays settled.
This can be the time to repot, and give your plant a whole container of fresh soil mix. A good potting blend will already have a nice balance of drainage materials mixed in, or you can add some extra bark or vermiculite to keep things really light.
While you are doing this, it can’t hurt to give your houseplants a little more leg room and go for a bigger pot. If they are still doing fine in their current container, feel free to just freshen up the soil and put them right back in.
Be Careful Not to Over Aerate
While having loose aerated soil is vital, you can’t overdo it at the expense of the nutrients. Many of the materials mentioned earlier are fairly inert and don’t add minerals to the soil.
In other words, if you have really loose soil filled with perlite or sand, that is great for the aeration but will not have the organic content a plant needs for nutrients.
Plants may get their food primarily from the sun via photosynthesis, but there is more to proper nutrition than just fuel. And the only place a plant can get these additional minerals is from the soil.
A typical plant will need to have a supply of calcium, phosphorus, nitrogen, potassium, magnesium and a lot more in order to stay healthy.
And when you don’t have enough organic material in the soil to provide this, then you either replace with fresh soil or start using some fertilizer. There are a number of options out there for good houseplant fertilizer and you should read a few labels before making your choices.
Most commercial products will have 3 numbers on the label, giving you a ratio of the compounds inside. The first number is nitrogen (N), the next is phosphorus (P) and the last is potassium (K). Standard all-purpose mixtures will have the numbers all the same, such as 5-5-5 or 10-10-10.
For any houseplants that you grow for their lovely green foliage, you should use a little extra nitrogen. On the other hand, flowering or fruiting plants thrive with more phosphorus.
Compost or aged manure is a great way to add more nutrients too, but can be a bit awkward to use for indoor houseplants. Sticking with commercial blens is easiest. Just follow the directions for mixing and application.
There is one warning to the discussion about nutrients though, and that is to remember that not all plants require precisely the same mix of chemicals in their soil. In particular, some desert plants are perfectly fine with very sandy soil that is practically bare of nutrients.
Adding too much fertilizers in this case would do the plant harm.
What About Outside?
Compaction in the soil can happen outside too, even if you have a healthy population of worms and insects living in the garden. It can be the biggest issue with the lawn, and all that close-growing grass means you don’t have much access to the soil to do anything about it.
Rather than soil amendments in this case, it makes more sense to go with a more mechanical approach.
Powered machines that look like mowers or roto-tillers pass over the lawn, poking holes as they go. This helps bring air below the surface and will improve the health of the lawn, especially in the spring when there is a layer of thatch on top from the dead grass and debris.
Now you are fully familiar with aerating your potted plants, as well as some of the other details about keeping your soil happy for your houseplants.