3D Cartoon Plant Getting Watered by Rain

Watering Plants – A Deep Dive.

A Guide to Watering Plants
Reading Time: 11 - 14 minutes (3137 words)

In the intricate dance of life, water is the rhythm that sustains and nurtures. When it comes to plants, the act of watering goes far beyond a mere sprinkle or pour. It's a complex interplay of biological processes, physical properties, and environmental influences. "Watering Plants - A Deep Dive" ventures beneath the surface, unearthing the science and art behind osmosis, wicking, and the multitude of methods that ensure our leafy companions not only survive but flourish. Whether you're a seasoned gardener or a budding plant enthusiast, this exploration promises insights that will redefine the way you view that watering can and the life it sustains.

Foundational Concepts for Indoor Watering

Water Holding Capacity (WHC)

The Water Holding Capacity, often abbreviated as WHC, refers to the amount of water a particular growing medium can hold. The medium's WHC is largely determined by its particle size and composition, and this understanding becomes critical when choosing the best medium for your indoor plants regardless of whether you bottom or top water your plants.

Key WHC Takeaways:

  • Natural Soils:
    • Sandy soils: Characterized by larger particle sizes, they have a lower WHC. This means they dry out faster and require more frequent watering.
    • Clay soils: These have finer particles, leading to a higher WHC. As a result, they retain moisture for longer periods, which can be both an advantage and a challenge if not managed correctly.
    • Loamy soils: Combining the best of sandy and clay soils, they offer a balanced WHC, making them a favorite among many gardeners.
  • Indoor Grow Mediums:
    • Coir (Coconut Fiber): Derived from coconut husks, coir has a moderate to high WHC. It is excellent for retaining moisture while also offering decent drainage.
    • Peat: Similar to coir in its WHC, peat can hold substantial amounts of water. However, it tends to be more acidic, which can influence the pH levels of your setup.
    • Perlite: These white, porous particles are used to increase aeration and decrease the WHC of a medium, making them ideal for plants that prefer well-drained soil.
    • LECA (Light Expanded Clay Aggregate): While LECA balls can hold moisture, their primary role is to improve aeration and reduce the overall WHC of the medium.
    • Pon (Pumice or Lava Rocks): These have a moderate WHC, but they shine in providing excellent drainage and aeration.

When setting up your indoor garden, understanding the WHC of your chosen medium will guide your watering frequency and amount. Matching the right medium with the specific needs of your plants, as well as your personal water management practices, can be the difference between a thriving indoor garden and a struggling one. Remember, the essence of impeccable plant care lies not just in watering but also in understanding the environment in which your plants are growing.

Grow Media Porosity and its Impact on Watering

Porosity, in the context of a growing medium, quantifies the void or pore spaces within a specific medium, or the average of the soil mix if it's a mixture of different grow media elements (i.e. Peat or Coir, Perlite, and Fir Bark). It's an instrumental factor to understand in that it directly governs both the retention of water and the provision of oxygen.

Key Takeaways for Porosity:

  • Balancing Act: A medium with higher porosity tends to offer greater aeration and oxygen supply to the plant roots, fostering healthier root systems. Conversely, these mediums might not retain water as efficiently, necessitating more frequent watering or the need for complementary strategies.
  • Popular Indoor Grow Mediums:
    1. Coir (Coconut Fiber): Derived from the husk of coconuts, coir boasts excellent water retention while offering moderate porosity. It’s widely favoured for its environmentally friendly nature and pH neutrality.
    2. Peat: Often compared to coir, peat moss is a natural, organic material. It provides excellent moisture retention but may be slightly acidic. Its use often sparks ecological concerns due to its source from non-renewable peat bogs.
    3. Perlite: Recognizable by its white, porous, and lightweight granules, perlite is volcanic rock that has been superheated. It introduces high porosity into mixes, ensuring superior aeration while reducing water retention.
    4. LECA (Lightweight Expanded Clay Aggregate): These are round clay pellets baked at high temperatures to become lightweight and porous. Often used in hydroponics, LECA balls provide good aeration and can act as a semi-hydroponic growing medium.
    5. PON (Pflanzsubstrat Ohne Nährstoffe or Plant Substrate Without Nutrients): Commonly used with semi-hydroponic systems, PON is a blend of inorganic materials providing high porosity. It offers a robust drainage system, minimizing risks of root rot.
  • Choice Influences Outcome: The selection of growing medium is not just about plant preference but also about the environment. Factors like ambient humidity, local water quality, and the specific needs of a plant should guide decisions. For instance, in drier climates or environments, mediums like coir or peat that retain moisture might be preferable, whereas in more humid conditions, perlite or LECA may be more suitable to prevent overwatering and root rot.

Water Perching Tables

Water tables, while essential in the larger landscape of agriculture, have a micro version in our indoor potted plants, often referred to as 'perched water tables.' It's a layer of water that typically settles at the bottom of the pot, unable to drain due to gravitational forces and medium characteristics.

  1. The Importance of Proper Drainage:
    • Pots with Adequate Drainage Holes: Without these, water can easily stagnate at the pot's base, leading to potential root rot.
    • Saucer Management: While saucers are excellent for catching excess water, leaving water stagnant in them can create a stagnant pool beneath the pot. Empty these regularly.
  2. The Role of Growing Medium:
    • Coir and Peat: These organic materials are known for their excellent water retention capabilities as discussed above. However, they can compact over time, possibly leading to challenges with the water table.
    • Perlite: A porous volcanic glass, perlite ensures better drainage and reduces the likelihood of water tables forming.
    • LECA (Lightweight Expanded Clay Aggregate): As mentioned several times already, these are spherical clay pellets that allow for excellent water and air flow, significantly minimizing the chances of water stagnation.
    • PON: it's a mineral-based growing medium with optimal water retention and drainage properties, reducing the chances of perching water tables, similar to how LECA works.
  3. Understanding Media Interaction:
    • Combining mediums, like coir with perlite or LECA with peat, can provide an optimal balance between water retention and drainage, thereby reducing the risks of water table formation.

By being aware of the idiosyncrasies of each growing medium and understanding how they interact with water, indoor gardeners can effectively mitigate the risk of perching water tables and ensure their plants' optimal health.

Wicking in Various Grow Mediums

Wicking is the capillary action that causes water to travel upwards through a growing medium. While this might sound rather basic, the efficiency and effectiveness of this capillary action vary vastly depending on the medium used. Understanding how different indoor grow mediums handle wicking can guide decisions, ensuring optimal hydration and preventing overwatering.

Coir (Coconut Fiber):

  • Wicking: Coir wicks water efficiently due to its fibrous nature. This means that when using coir, bottom watering can be particularly effective as the water will travel upwards, hydrating the root zone.


  • Wicking: Peat’s spongy nature allows it to absorb and distribute water evenly. Its wicking action is steady, making it a reliable medium for consistent moisture delivery.


  • Wicking: While perlite itself does not retain a lot of water, its porous nature aids in distributing moisture when mixed with other mediums. It’s often blended with peat or coir to balance water retention with good drainage.

LECA (Light Expanded Clay Aggregate):

  • Wicking: LECA's large pore spaces and unique shape make it an efficient wicker. When used in semi-hydroponic systems, LECA can transport water from the reservoir to the plant's roots efficiently, ensuring constant moisture availability.

PON (Plant Optimization Nourishment):

  • Wicking: Due to its well-balanced mix, PON offers controlled wicking. It neither holds too much water nor drains too quickly, making it suitable for a wide range of plants.

Key Takeaways:

  1. Different mediums, Different Wicking Capabilities: Every medium has its unique wicking characteristics. Choose based on the hydration needs of your plant and your watering habits.
  2. Mix and Match: Combining mediums can optimize wicking. For instance, adding perlite to coir can enhance aeration while maintaining efficient wicking.
  3. Mind the Roots: While wicking ensures the soil remains moist, over-reliance can cause root rot. Balance is key. For water-loving plants, efficient wicking mediums like peat, coir or LECA might be ideal. For those that appreciate drier conditions more porous media choices could be better.


Osmosis is not merely a term that you'd come across in a biology textbook; it plays an essential role in determining how plants in different growing mediums absorb water. At its core, osmosis is the movement of water across a semi-permeable membrane driven by differences in solute concentrations. While plants don't have what we typically consider "membranes," their roots essentially function as one, filtering what gets in and what stays out. This process ensures that plants receive the right amount of moisture without being overwhelmed.

The Role of Osmosis in Various Indoor Grow Mediums:

  1. Coir: Derived from the husk of coconuts, coir has a neutral pH and significant WHC. Osmosis in coir works efficiently, as its structure allows for excellent moisture retention. However, given its water retention properties, ensuring that it doesn't become waterlogged is pivotal.
  2. Peat: Peat moss, often considered the gold standard in moisture retention, facilitates osmosis by maintaining a consistent moisture level around the roots. It's organic and holds water better than most mediums, providing plants a steady supply for osmotic absorption.
  3. Perlite: This is a volcanic glass that has been super-heated into tiny white balls. Perlite is porous, so while it aids in water drainage and aeration, it doesn't retain much moisture. Consequently, osmotic absorption is most efficient when perlite is combined with other mediums to balance out its rapid drainage.
  4. LECA (Lightweight Expanded Clay Aggregate): These clay balls serve as a hydroponic medium, facilitating steady water supply to the plant roots. Given that the medium itself doesn't retain water but facilitates its flow, plants growing in LECA are highly dependent on osmosis for their water needs.
  5. PON: PON is a mineral-based substrate. It allows for a gradual release of water and nutrients. Due to its slow-release mechanism, osmotic uptake in PON is a gradual process, ensuring the plant roots never remain waterlogged.

Key Osmosis Takeaway

Osmosis is the silent process ensuring that our indoor plants, regardless of their medium, remain hydrated and nourished. Different mediums might alter the speed or efficiency of osmotic uptake, but they all rely on this fundamental biological process. As an unlikley gardener, recognizing the intricacies of osmosis in varied grow mediums allows for more informed watering decisions, ensuring our indoor green companions don't just survive but truly thrive.

Osmosis vs. Wicking: The Fundamental Differences

Water movement is vital for plants, and understanding the distinctions between osmosis and wicking (or capillary action) is paramount for gardeners, botanists, and anyone curious about the inner workings of nature. While both processes transport water, they function differently and serve distinct purposes.


Definition: Osmosis is the movement of water molecules across a semi-permeable membrane from a region of lower solute concentration to one of higher concentration.

Primary Role in Plants:

  1. Nutrient and Water Uptake: Osmosis governs the movement of water (along with dissolved nutrients) from the soil into plant roots. This water movement is driven by the concentration differences between the soil solution and the cell sap inside the plant's roots.
  2. Turgor Pressure Maintenance: Osmotic movement of water into plant cells helps maintain their turgidity or rigidity. It's crucial for structural support and plays a role in the opening and closing of stomata, which controls gas exchange.

Key Features:

  • Involves a semi-permeable membrane.
  • Driven by differences in solute concentrations.
  • Ensures the cell's internal environment remains stable.

Wicking (Capillary Action)

Definition: Wicking or capillary action refers to the ability of a liquid to flow in narrow spaces against external forces like gravity, often due to the cohesive and adhesive properties of the liquid.

Primary Role in Plants:

  1. Water Movement in Soil: Capillary action aids in distributing water evenly through the soil. This ensures that water is available to a greater volume of roots even after the gravitational water has drained away.
  2. Water Transport in Plants: While the primary force moving water up a plant's xylem is transpirational pull, capillary action plays a supplemental role, especially in tiny plant capillaries.

Key Features:

  • Doesn't require a membrane.
  • Driven by adhesive and cohesive forces of the liquid.
  • Vital for distributing water in the soil and within some parts of plants.

Wicking /Osmosis Summary

While both osmosis and wicking deal with the movement of water, they are inherently different processes. Osmosis is centered around balance and equilibrium within biological systems, ensuring cells remain hydrated and nourished. In contrast, wicking or capillary action, driven by physical properties, ensures water's efficient distribution in soils and small channels in plants. Recognizing these differences allows us to appreciate the intricate and diverse mechanisms that nature employs to nurture and sustain life.

Watering Indoor Plants: Mastering the Basics

The majority of this article may have felt like taking a drink from a fire hose, but with watering being the #1 cause of plant stress, and ultimate death, knowing the technical foundations for how water works within and around various substrates is critical. Otherwise what seems like a pretty straightforward task, when it comes to indoor plants, can result in complete plant and indoor gardening failure.

Overwatering and underwatering are two of the most common pitfalls unlikely gardeners and plant enthusiasts face. But fear not, this deep dive into the foundational understandings and your keen eye, you can now be confident that your leafy friends remain hydrated and happy. Here’s a quick but definitive guide to mastering the basics of watering indoor plants.

1. Understand Your Plant’s Needs

Different plants have different watering requirements. Succulents, such as aloe vera or cacti, store water in their leaves and therefore need less frequent watering compared to tropical plants like ferns, alocasias, or pothos, which prefer consistent moisture.

Tip: Always research the specific needs of a plant when you bring it home. This will provide a baseline to work from.

2. Check the Soil

The best way to determine if your plant needs water is to check the soil. Insert your finger about an inch into the soil. If it feels dry, it's time to water. If it's still moist, hold off. Keep in mind the concept of a perched water table however, if that marker is below your finger depth then its still easy to overwater.

Tip: Don’t rely on scheduled watering. Always let the soil be your guide.

3. Water Thoroughly

When watering, ensure that the entire root ball gets wet. Water should come out of the drainage holes at the bottom of the pot. This not only ensures that the roots are getting the necessary moisture but also helps flush out any accumulated salts.

Tip: If the water runs straight through without being absorbed, the soil may be too dry, causing it to repel water. In such cases, place the pot in a basin filled with water to allow the soil to absorb moisture from below. Bottom watering has its place, especially when it comes to hydrophobic grow mediums.

4. Use the Right Tools

A watering can with a long spout helps direct water to the base of the plant, preventing moisture from resting on the leaves, which can lead to mold and other issues. For plants with deeper pots, consider using a soil probe to ensure water reaches the bottom layers. This is not a moisture tester, it's just a way to directly deliver water to lower regions.

5. Mind the Temperature and Quality

Plants tend to prefer lukewarm or tepid water over cold. Cold water can shock their roots, hampering growth. Additionally, some plants are sensitive to chemicals commonly found in tap water. If you notice your plant reacting negatively after watering, consider using filtered or using distilled water.

6. Pay Attention to Humidity

Some tropical plants, like orchids or calatheas, thrive in higher humidity levels. If you live in a dry climate or are running heating during the winter, consider using a warm-mist humidifier. Many people mist their plants or place a tray filled with pebbles under their plants to boost humidity, but these techniques are more myth than fact.

7. Adjust Watering With the Seasons

Plants generally need less water in the winter months when they’re dormant or growing more slowly. Similarly, during the growing season (typically spring and summer), their water needs may increase. Be attentive to these shifts. These may not be applicable if you are growing indoors in a well maintained enviroment, so keep that in mind.

8. Beware of Overwatering (this should probably be #1 thru #10)

While it's essential to provide plants with adequate moisture, overwatering can lead to root rot – a deadly condition. Signs include yellowing leaves, a sudden droop, or a moldy smell emanating from the soil. Ensure pots have adequate drainage and avoid letting plants sit in water.

Overwatering isn't really the problem, but it contributes significantly to the chances of creating an oxygen deprived environment for your plants' roots.

Watering Plants - The Conclusion

Mastering the act of watering plants is akin to understanding the very essence of life itself. Through our unlikely journey, we've delved into the microscopic intricacies of osmosis, the physical marvels of capillary action, and the practicalities of understanding various watering considerations across various media. We've recognized the profound importance of choosing the right grow medium and addressed concerns that often factor into your plants' health and happiness. Moreover, we've learned that beyond the act of quenching a plant's thirst, the choice of water and its mineral content can play pivotal roles in plant health. Providing optimal moisture levels means every drop counts.

Watering plants is not just a chore or routine, it's a critical interaction with nature, a responsibility, and an art. So, the next time you water your plants, remember you're not just hydrating them, but participating in a ritual that bridges humanity and nature in the most nurturing way possible.

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