Potting Soil Won’t Absorb Water? Reasons and What to Do

Water running straight through soil is a common problem in container gardening. This is when potting soil won’t absorb water causing it to quickly run through and out of the bottom of the pot. This can lead to plants not getting the water they need to survive, resulting in yellowing, wilting, and even death of the plant.

Common reasons why soil won’t absorb water include hydrophobia, compaction, high clay content, salt or waxy buildup, poor drainage, old and poor soil structure, air pockets in the soil, and incorrect potting soil for the plants.

Generally, potting soil is designed to be well-draining and hold a sufficient amount of water to support plant growth, without becoming waterlogged. The University of California, Division of Agriculture and Natural Resources note that many potting soils containing peat moss tend to repel water when they dry up.

If the soil does not absorb water well, the plant’s roots may not be able to access the water they need for healthy plant growth. Additionally, soil that does not absorb water well can lead to issues with mold and fungus growth, which can also harm plants.

Why potting soil won’t absorb water

If water is running straight through the potting soil or sitting at the top and not being absorbed, it could be due to a few factors:

Poor soil structure

Potting soil without enough drainage abilities may cause water to run straight through it instead of being absorbed. Good potting soil should hold moisture and nutrients at the same time allow water and air to pass through it.

Over-watering

Potting soil that is already saturated with water, may not be able to absorb anymore. It is important to allow the top inch of soil to dry out before watering again.

Hydrophobic soil: Potting soil may repel water due to a waxy buildup in the upper layer. This may result from microbial activity or the presence of too much salts in the soil.

Soil dryness

Soil that is extremely dry may not be able to absorb water easily until it has had a chance to rehydrate. This problem can easily be solved with a bottom-watering approach.

Air pockets

While oxygen is essential for root growth, air pockets may inhibit the flow of water in the soil. Aerating the soil with a fork or trowel can help improve water absorption.

Soil type

Potting soil that is high in clay or sand can have difficulty absorbing water. Clay has closely packed particles that can prevent the natural flow of water. On the other hand, sand does not have any ability to hold moisture and water will typically pass straight through it.

Soil compaction

Soil becomes compacted when its particles are pressed together blocking or reducing any pores between them. This can happen if the soil is over-watered or if it is not mixed well before use.

Note that, bottom watering not reaching the top is also a sign that potting soil is not absorbing the water. Typically this method is suitable for rehydrating hydrophobic soils as explained in the video below:

How to fix potting soil that won’t absorb water

If potting soil is not absorbing water there are a few steps you can take to fix the problem:

1. Aerate the soil: Use a fork or a trowel to gently loosen the potting soil. This will help to improve water absorption but be careful not to damage the plant roots.
2. Add organic matter: Mix in some organic matter, such as peat moss or compost. This will help the sandy soil hold enough water for the plants.
3. Check drainage: Make sure the pot has enough drainage holes at the bottom and that the soil is not compacted.
4. Water appropriately: Water the soil thoroughly, but do not over-water. Allow the top inch of soil to dry out before watering again.
5. Add water-retention agents: You can add water-absorbing polymers to the soil, which can help to retain water and make it available to the plant roots.
6. Re-potting: If none of the above methods work, then repot the plant in fresh potting soil. Ensure the new soil and pot has good drainage abilities.

Final Thoughts

Water is a key requirement in the process of photosynthesis where plants make their own food. Soil not absorbing water is a big threat to the health of a plant. We have seen that this problem may occur as a result of poor soil structure, incorrect watering, waxy buildup in the soil, and using the wrong type of soil for your plants.

When growing your plants, it is important to ensure that the potting soil is well-draining, has the right amount of organic matter, and is not compacted to make sure that it absorbs water properly. If the problem persists, you may need to repot the plant in fresh potting soil.