As plant owners, we tend to focus on soil, sunlight, and fertilizers, but there’s another crucial factor for plant health that sometimes slips through the cracks: water quality. Water is fundamental to plant growth, and its composition can have a significant impact on your plants. A common dilemma is whether or not to use softened water for plants. Soft water is usually preferred for household use, but what about our leafy friends? 

In April of 2023, our CPO, Jesse, lost his Alocasia Melo (RIP). 

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This began one of Team Krado’s biggest mysteries to date. The Alocasia in question had one of our sensors in the soil, and was otherwise completely healthy–so what happened? One thing our sensors can’t do (yet) is account for soil salinity or pH.

As we solve the mystery of what happened to Jesse’s Alocasia Melo, this article will also delve into the realm of soft water and its effects on plants. We'll explore what soft water actually is, understand its role in plant health, and uncover the reasons why certain plants are sensitive to it. Additionally, we will discuss viable alternatives and solutions to mitigate any adverse effects, ensuring that your plants thrive. Whether you’re a houseplant enthusiast or an experienced gardener, this comprehensive guide will provide you with the insights needed to make informed decisions about watering your plants with soft water. Let's dive in!

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The Mystery of the Alocasia Melo

At team Krado, we’re all about data.  So when Jesse’s Alocasia Melo died, we turned to the data to learn what went wrong. Leaflet sensors are gathering data in real-time, all the time. This allows us to stop problems before they start. Is your plant getting too much light? Your sensor will let you know in real-time. So with Jesse’s Alocasia, naturally we were curious. What went wrong, and what will the data tell us? 

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Look to the Data

At Krado, we give you real-time insights on your plant’s health so you’re never left guessing. Leaflet translates your plant’s moisture, temperature, light, humidity, DLI, & VPD, and on your end the data looks a little like this: 

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When Jesse’s Alocasia Melo died, we looked at the raw data, so Team Krado could get to work identifying any potential causes. It looks like this:

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The variables we had to work with were moisture, light, humidity, and temperature. We then calculated DLI (Daily Light Integral)] and VPD (Vapor pressure deficit). Learn more about DLI here. 

The group started to diagnose the issue:

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Quino accurately pointed out that we can’t troubleshoot lack of nutrients with this data. Unfortunately this version of our sensor isn’t equipped with a nutrient sensor (that’s coming at a later date!).

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Jesse shared a new photo of the root ball to help further diagnose. 

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Suddenly, a wild lead appears! Could the cause of death be soft water?

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So team Krado sent the soil off to be tested. More on that and the results later. For now, let’s get into soft water and your plants. 

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Understanding Soft Water

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What is soft water?

Soft water has low concentrations of ions, particularly metals such as calcium and magnesium. These are the minerals typically responsible for what we refer to as water "hardness." In other words, soft water is water that has been effectively stripped of these minerals.

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How is soft water created?

There are two methods of creating soft water, natural and artificial. Natural soft water is present in rainfall, and doesn't contain high levels of dissolved minerals. Artificially softened water, on the other hand, is the result of a process known as water softening. This process involves running hard water through a unit that contains resin beads carrying sodium or potassium ions. These ions are then swapped for the calcium and magnesium ions in the hard water, resulting in soft water.

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What are the components of soft water?

Soft water primarily contains sodium ions after the softening process. While this is beneficial for preventing mineral build-up in pipes and appliances, high sodium content may be harmful for plants, which we will discuss further in the upcoming sections.

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The Impact of Soft Water on Plants

Various research studies show the detrimental effects of soft water on plants. For instance, a study by the University of Pennsylvania revealed that plants watered with soft water exhibited reduced growth rates compared to those watered with hard water. The study attributed this effect to the high sodium content in soft water.¹

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How the sodium in soft water can harm plants

Soft water is typically high in sodium ions. When plants are watered with soft water, the sodium content can increase in the soil, which can cause two main issues:

1. Sodium competes with the plant's roots for water. Too much sodium can cause a condition known as “physiological drought”, where the roots are unable to take up water efficiently, even when water is readily available.
2. High sodium levels can lead to the displacement of essential nutrients in the soil. Sodium ions compete with potassium ions, which are critical for many plant functions such as protein synthesis, enzyme activation, and stomatal regulation.

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The effects of excessive sodium on plant health

High sodium levels can also cause nutrient imbalances, leading to deficiencies of other essential nutrients. In extreme cases, it can result in plant death.

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Salt burn

Salt burn, also known as leaf scorch, is a common symptom of sodium toxicity in plants watered with soft water. When the sodium concentration in the soil solution becomes too high, it leads to a burnt appearance around the leaf margins. The edges may turn yellow or brown and eventually become dry and brittle.

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Stunted growth

Another symptom of excess sodium in the soil from soft water is stunted growth. This phenomenon, known as 'physiological drought,' can lead to water stress, even when the soil is sufficiently moist. The plant's growth may slow down as a response to this stress, leading to shorter, smaller plants with reduced biomass. Over time, this can impact the plant's reproductive capabilities, leading to fewer, smaller, or no flowers and fruits.

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Nutrient imbalance

The use of soft water can also lead to nutrient imbalances in the soil. As mentioned, sodium ions in the softened water can compete with other essential ions, like potassium, for uptake by the plant's roots. Nutrient imbalances can lead to a range of growth problems, from discolored or distorted leaves to reduced resistance to pests and diseases. In extreme cases, nutrient deficiencies can even result in the death of the plant.

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Soft Water vs. Hard Water for Plants

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Effects of soft water and hard water on plants

The main difference between soft water and hard water when it comes to plant health is the mineral content. Soft water, as we've discussed, contains higher levels of sodium and lower levels of beneficial minerals such as calcium and magnesium. 

Hard water, on the other hand, contains higher concentrations of calcium and magnesium. These minerals are beneficial to plants as they contribute to cellular structure and photosynthesis.

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Why are some plants more sensitive to soft water?

Specific plants may be more sensitive to soft water due to their unique physiological traits and nutrient requirements. Here are a few reasons:

1. Sodium Sensitivity: Some plants are particularly sensitive to sodium. High sodium levels in soft water can interfere with these plants' ability to take up water and essential nutrients from the soil.
2. Nutrient Requirements: Plants have different nutrient needs. Those that require higher levels of calcium and magnesium - nutrients typically found in hard water but missing in soft water - may struggle more when watered with soft water.
3. Water Uptake Mechanisms: Different plants have varying mechanisms for absorbing and transporting water. Some are more efficient at excluding or expelling excess sodium, while others may take up too much, leading to toxic levels in their tissues.
4. Plant Structure and Physiology: The physical structure and physiological characteristics of a plant can also influence its sensitivity to soft water. For instance, plants with fine, fibrous roots have a large surface area for water uptake and may absorb sodium more readily. Similarly, plants with succulent leaves might store more water (and hence, sodium), making them more prone to sodium toxicity.
5. Tolerance to pH Changes: Soft water tends to be neutral to alkaline, and some plants may struggle with these pH levels. Many plants prefer slightly acidic conditions, which enable better nutrient availability and uptake.

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Soft Water Effects on Hydroponics

Hydroponics face similar challenges with soft water. At-home hydroponics systems are designed to create an optimal growing environment for plants, providing them with the right balance of nutrients, light, and air. These systems are typically engineered with a one-size-fits-all approach, operating under the assumption that all inputs, including water, are standardized. 

However, this ignores the fact that water quality varies significantly across different regions. The hardness or softness of water, the pH level, and the presence of certain minerals or other substances can differ drastically depending on the local water supply. This variability can lead to unexpected challenges when using at-home hydroponic systems. For instance, using hard water could lead to mineral buildup in the system, while using soft water might necessitate additional supplementation of essential nutrients. 

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It’s official: Soft water is killing your plants 

So what happened to Jesse's Alocasia Melo? Let's take a look at the "autopsy." 

TLDR: The results show very high soil salinity.

It’s official: death by salt.

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Soft water: A delayed death sentence for plants?

Jesse's Alocasia Melo wasn't the only plant to suffer the effects of soft water. Below are several pictures of Jesse’s plants, all struggling with salt burn, stunted growth, as well as nutrient imbalance.

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It’s official. Soft water is a delayed death sentence for plants. It takes a while but it just happens all at once! Do these pictures look familiar to you? Your plants may be suffering from soft water poisoning. How can you mitigate the effects of soft water on your plants?

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Mitigating the Effects of Soft Water on Plants

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Alternative Water Sources

The easiest, most effective way to mitigate the effects of soft water is to simply not use it. Some other sources of water you can use on your plants are: 

    •    Rainwater

Rainwater is a great option as it's naturally soft but doesn't contain the high sodium levels found in artificially softened.

    •    Filtered Water

If sodium levels in your soft water are excessively high, you may want to consider investing in a reverse osmosis system. These systems can effectively remove sodium, providing you with a cleaner water source for your plants.

    •    Distilled Water

Distillation is a process that removes nearly all minerals and impurities from the water, including sodium. This results in pure water that won't contribute to sodium buildup in your soil. However, because distilled water is devoid of any minerals, it's important to ensure your plants receive necessary nutrients from another source, typically the soil or a nutrient-rich fertilizer. 

    •    Tap Water

If using tap water, allow it to sit out for a day or two before watering plants. This process can allow some of the sodium to evaporate.

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How to safely use soft water for plants

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Choose Soft-Water Tolerant Plants

If soft water is your only option, consider choosing plants that are more tolerant of these conditions. Certain plants, such as those native to coastal regions or areas with high rainfall, may be naturally more tolerant of higher sodium levels.

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Can I save my plant after soft water poisoning? 

The short answer is yes. Check out this step-by-step guide where Jesse saved some of his plants. Click here for a detailed step-by-step guide.

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Q & A

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What is soft water? How do you make water soft?

Soft water is water that has low concentrations of ions, especially ions of calcium and magnesium. It's typically achieved naturally through rainfall or artificially through a process called water softening where calcium and magnesium ions are exchanged with sodium ions.

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Is soft water bad for plants?

Soft water can potentially cause issues for some plants due to its high sodium content and lack of essential minerals such as calcium and magnesium. The sodium can lead to toxicity in plants, causing symptoms like leaf scorch and stunted growth.

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Can You Use Soft Water in Hydroponics?

You can use soft water in hydroponics, but it requires careful management and supplementation with missing nutrients, as soft water is typically low in calcium and magnesium. High sodium levels in some types of soft water can also pose a problem in hydroponic systems.

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What are Symptoms of Sodium Toxicity in Plants?

Symptoms of sodium toxicity in plants include leaf scorch (also known as salt burn), where leaf edges turn brown or yellow, stunted growth, and nutrient imbalances which can manifest as chlorosis or necrosis in the leaves.

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Do Indoor Plants Prefer Soft or Hard Water?

The preference of indoor plants for soft or hard water largely depends on their species and native habitats. However, most common houseplants tend to do better with water that's somewhere in between - not too hard and not too soft.

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What is the Impact of Soft Water on Soil Health?

Soft water can lead to an increase in the soil's sodium content, which can alter soil structure and negatively affect its health. It can also cause nutrient imbalances due to the lack of calcium and magnesium and the potential for sodium to compete with other essential nutrients for uptake by plants.

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What if I use potassium chloride instead of sodium chloride in my water softener?

Using potassium chloride instead of sodium chloride in your water softener can be a beneficial alternative for both your health and your plants, however, it can be more expensive than traditional softener pellets. Many water softening systems are compatible with potassium chloride pellets as an alternative to traditional sodium chloride. Given that potassium is a crucial nutrient for plants, employing potassium chloride softened water can be a safe and beneficial choice for watering your houseplants and enriching your soil.

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Is it okay to water plants with soft water?

Watering plants with soft water is not recommended, as some types of artificially softened water contain high levels of sodium, which can lead to toxicity in plants if used consistently over time. Symptoms of sodium toxicity include leaf scorch, stunted growth, and nutrient imbalances.

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How do you remove salt from softened water for houseplants?

You can remove excess salt through a process known as reverse osmosis. Reverse osmosis systems force water through a membrane that filters out salts and other contaminants.

Alternatively, you can dilute the softened water with rainwater or distilled water to reduce the overall sodium content.

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What is the best water for plants?

Rainwater is often considered ideal for most plants because it is naturally soft and does not contain added chemicals found in tap water. The best water for plants typically falls somewhere between hard and soft water.

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Citations

1. ​Penn State News. (n.d.). Softened water can cause hard times for indoor plants. Penn State University. https://www.psu.edu/news/agricultural-sciences/story/softened-water-can-cause-hard-times-indoor-plants/

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