You go to water your potted plant as usual and find that the water just runs out of the drainage holes from the bottom. And that’s a bad sign that you need to fix something.
Water goes right through your plant because the potting soil has become hydrophobic. This means the soil cannot absorb the water and it just drains out. The reasons why this happens could be a lack of beneficial organisms, soil compaction, or mineral build-up in the soil.
I’ve written all the details below to help you figure out the root cause of this problem and what you can do to improve your potting soil.
Potting Soil that Has Become Hydrophobic
The most common reason why water runs right through is that the soil has become hydrophobic. This means it cannot absorb the moisture as it used to.
The main reason this happens is that you have not watered the potting soil regularly. So the materials like peat moss turn hydrophobic.
Such material tends to be hydrophilic and has good moisture-absorbing properties. It slowly releases the moisture back to the plant’s roots. But once you stop watering such material, it will become hydrophobic and not absorb the moisture.
Another reason soil becomes hydrophobic is due to the loss of essential bacteria and fungi. This can happen for the same reason that the soil has not received sufficient watering and has gone dry.
The solution to this problem is to try and make the soil hydrophilic again. You can do this by adding organic material like compost. Compost is jam-packed with all those great microorganisms (bacteria and fungi) that will restore the vitality of your soil and its absorbency.
You can integrate this with your soil or scatter it on top; however, in severe cases of hydrophobic soil, remove the top couple inches of soil and replace it with nutrient-rich compost.
An alternative to this is compost tea, which is the liquid produced by the end of the decomposing process (when all the organic matter is broken down).
If the potting soil has peat moss that has turned hydrophobic, you need to soak the entire pot in a tub. Let it soak for an hour so the material can slowly absorb the moisture and retain its hydrophilic properties.
When your soil is hydrophobic, you might notice how the water pools together above the soil due to surface tension paired with the fact that the hydrophobic soil won’t draw in and absorb this water. This little pool will stay like this until, eventually, the water drains through the pot.
A wetting agent can fix this. It is a chemical surfactant that destabilizes/ decreases the surface tension of water. That means it won’t pool together so much and distribute itself more evenly, clinging to the soil and promoting hydration.
A common household wetting agent is dish detergent (organic is best). Just make sure to use a mild kind, and dilute a few drops in a gallon of warm water and pour it on top of the plant.
Also, you could add a natural wetting agent like peat moss, which is common in most potting mixes. Peat moss is super absorbent, but if you don’t want to repot your plant, then have a go with the detergent method or compost first.
The plant has become root-bound
When your plant is root-bound, it means that your plant has outgrown its pot and needs a new one. The easiest way to tell this is by checking the drainage holes at the bottom. The roots will have reached those holes and trying to come out of them.
Take note, however, if you can’t see the roots escaping, as it were, through the drainage hole of your plant, then it doesn’t necessarily mean you are in the clear. The roots might be so compact in the pot that you can’t see its overcrowding.
To check, gently turn the plant upside down and slide it out of its pot to check the roots. If the plant is indeed root-bound, you’ll see the roots outlining the edges of the soil.
There is a simple way to cure this ailment, and that is to move the plant from its current pot to one that is at least 2 inches wider (4 inches maximum), preferably a terracotta pot as its porous nature always the plant to breath better.
Once the plant is out of the pot, try to gently separate the roots as much as possible. You may need to trim a layer of the roots if they are stuck to the soil.
Get a larger pot that can hold the plant. You can soak the pot in a solution of 1 part bleach and 9 parts water to sterilize it. Soak the pot for at least an hour and then you can rinse it with clean water. Let the pot dry before you can put the plant in it.
Add potting soil to the new pot till you have filled it and just 1-2 inches of space is remaining at the top of the pot. Dig a hole in the center of the potting soil and place the plant roots inside it.
Add potting soil to cover up the roots and firm near the base of the plant to give it good support. Water the potting soil well so the water flows out of the drainage holes at the bottom.
Potting soil has compacted
When part of your potted plant’s soil or the entirety of the soil has hardened like a stone, then you have compacted potting soil.
This problem might not be easy to catch as we can’t see into our pot’s soil, so many people only notice compacted soil when transferring their plant to a bigger pot (a plant transplant). But a good indication is when your plant stops absorbing water as well.
If you do have compacted potting soil, this is because the soil has become so hardened that it isn’t aerated enough – there aren’t enough gaps – for water to drain through it, so the water bypasses those clumps of soil altogether. As a result, your plant will be left dehydrated, which we don’t want.
Compacted potting soil occurs when the soil has dried out too much due to excessive sunlight and/ or insufficient watering. As a result, the microorganisms that are so essential to the life of your soil, and therefore your plant, perish.
So, to fix compacted soil, you’re going to need to reintroduce bacteria and fungi into your soil by adding nutrient-rich compost or compost tea. That broken-down organic matter (manure could also be used) is going to inject life right back into your soil, allowing it to withhold moisture, thus restoring the plant’s balance.
Mineral build-up in the potting soil
You can spot mineral build-up on your potting soil as it will cause a layer of white crystals on the soil’s surface. It might look like there is a white mold forming, but it is simply mineral deposits of salts and calcium caused when the soil hasn’t been drained often enough. This may especially be the case for some plants that require watering from below.
To get rid of mineral build-up, you’re going to want to flush your plant approximately once a month. You can simply pour a glass of water on the top for those plants that you water from below, and the salt and calcium should drain through. For plants that are used to be watered from above, you should flush the plant with the equivalent of two pots of water.
The best way to avoid hydrophobic soil is a regular watering schedule fitted to each of your plants (not all plants require the same amount of water). If you’re going away on vacation, then make sure to ask a friend to come by and water your plants and make sure they’re not getting too much sunlight as this can dry out the soil and kill those essential microorganisms.
When potting soil becomes hydrophobic and/ or compacted, it is essential to reintroduce microorganisms back into the soil using organic matter like compost, compost tea, or manure. These will allow the soil to aerate, creating little water pathways to drain through instead of running straight through your plant. Different wetting agents like peat moss or mild, organic detergents can also encourage the intermingling of water and the soil.
Root-bound plants might be tricky to catch, but this affliction is a sign that your plant needs a bigger home! Make sure to transfer your precious plant to a pot at least 2 inches bigger but not 4 inches. Keep a good eye on your plants and try to use the breathable terracotta pots as much as possible.