Any grower knows that under or overwatering water can cause many plant problems. It’s the reason for wilting and dying greenhouse cucumbers or why your eggplant is not flowering.
However, sometimes it doesn’t have anything to do with the amount of water. The problem can be with the soil that you use – it can get compacted.
Here’s an overview of why water runs straight through soil:
Most of the time, the water will run straight through the soil if the planting soil becomes compacted. It can happen when the plant grows too big for its pot, the potting mix becomes hydrophobic or the soil dries out. Repotting the plant into a bigger container or rehydrating a potting mix or soil should fix it.
Read on to learn more about the reasons why water runs straight through the soil and I’ll explain what to do to fix this problem and avoid it in the future.
Why is my potting mix dry after watering?
Most likely if the potting soil stays dry after watering, you didn’t use enough water. What you can do to check if you gave the plant enough water is to wait until the water starts dripping into the saucer beneath the pot.
If after several minutes there is no water in the saucer, you definitely need to water your potted plant more. But there can be another problem – your plant became rootbound.
It means that the roots of a plant take up the whole space in the pot. These roots are circling and create a dense web. So, the roots are too big for the amount of soil.
As a result, roots absorb water instantly and need more moisture. Most of the time it happens when you grow your plants in the same pots for a long time.
To check if your plant is rootbound, look at the hole at the bottom of the pot. Visible roots are a sign of a rootbound plant.
Moreover, you can carefully remove the plant from the pot when the soil is dry. If the roots cover the surface of the soil in circles and around the root ball, the plant is rootbound.
If that’s the case, you need to move the plant into a bigger container. If it doesn’t help, the problem with me with the soil repelling water.
Why does water run straight through the pot?
Have you ever noticed that sometimes after you water your potted plant the water quickly appears in the saucer, but on the next day the soil is dry again?!
It happens because the potting mix dried out and lost its ability to absorb water. That is why water goes right through the pot.
This potting mix became hydrophobic, which means that it repels water instead of absorbing it.
Commercial potting mixes often contain peat moss which is lightweight, retains water very well and decomposes slowly.
However, when peat moss dries out, it doesn’t absorb water and it’s hard to wet it again. If you water your plant irregularly or went on a vacation for a week or two, it can cause the potting mix to dry out.
So, when the potting mix is dry and you water it, soil barely absorbs water and it just runs down the sides of the pot into the saucer.
Some gardeners think that soil is saturated when water drains too fast. However, in reality, water is running between the sides of the pot. The plant roots hardly absorb any water and are left dead dry.
How to rehydrate a dry potting soil:
If you start to water dried out potting soil continuously, it won’t rehydrate potting mix. It is hard to wet peat moss once it dries out, so you will need to put the pot in a bucket of water. Here’s what you need to do:
Step 1: Put the pot in a bucket with water
Take a small pot and hold your hand over the top of the soil at the base of the plant to prevent the soil from washing away.
Immerse the pot in a tub or bucket filled with water. The pot will float at first because of too much air in the root ball.
Step 2: Hold the pot under the water
You will need to hold it under the water until bubbles stop floating to the top. Air bubbles coming out of the soil when soil is added to water mean that air in the soil is placed by water.
If the container is larger than 8 inches or you can’t lift it easily, you need to trickle water onto the soil. Take a hosepipe on a very low trickle and place it in the pot.
Water should fall in a slow stream, so it has time to absorb instead of running off. Also, you can set a timer to make sure that you are not going to overwater your plant.
Another way to rehydrate potting soil is to add a wetting agent to get the soil to absorb water. Soil wetting agent is a surfactant – a chemical substance that reduces the surface tension of water allowing it to spread onto a surface as a film.
Surfactants are used in the production of dishwashing liquid. So, a few drops of mild detergent in a gallon of warm water can be used as a wetting agent for plants.
Here’s how you can do it:
- Slowly pour this mix over the soil.
- Aim to wet all portions of the surface as much as possible.
- Keep in mind to stay away from the edges of the pot because that water will run straight through and won’t be absorbed.
It can work right away but repeat the procedure a few times over a couple of hours. It should rehydrate potting soil so it will start absorbing water.
TIP: Don't forget to remove the excess water from the saucer every time!
The good news is that most commercial potting mixes solve this problem for you by adding a wetting agent to the mix.
For example, Proven Winner Premium Potting Soil is a mix of peat moss, wood bark, perlite, dolomite lime, fertilizer and professional wetting agent.
That way you can grow flowers in pots and garden beds without worrying about potting mix holding moisture and draining well!
If you are growing in a greenhouse and water runs straight through soil, you need to check what type of soil you have in your garden.
Then, amend it to prepare the best soil mix for the greenhouse. If the soil is bad and you don’t want to spend too much time improving it, you can just build a raised bed and start growing!
Want more greenhouse tips, tricks, and ideas? Follow me on Pinterest!
Happy Growing 🙂
With Love,
Ana
