Whether bottled water is beneficial or detrimental to plants depends entirely on the purification method used and the resulting chemical composition. While many people consider store-bought water an upgrade from standard tap water, the complete absence of dissolved solids in some types can be just as problematic as an excess in others. The suitability of any water source is determined by how its specific mineral content and acidity align with the needs of the plant being watered. Ultimately, there is no single “best” water, only water that is chemically appropriate for a specific plant’s physiology.
Essential Needs of Plants From Water
Water acts as the transportation system within a plant, moving dissolved nutrients from the soil to the leaves. Beyond hydration, the two most important chemical properties water contributes to soil health are its pH level and the concentration of Total Dissolved Solids (TDS). The pH scale measures acidity or alkalinity, and most common garden and houseplants thrive in a slightly acidic to neutral range, typically between 6.0 and 7.5. This slight acidity optimizes the solubility of essential elements, making them available for the plant to absorb through its roots.
TDS represents the combined concentration of inorganic salts, minerals, and metals present in the water. These minerals, such as calcium, magnesium, and potassium, are nutrients that plants require for various cellular functions. Water with a very low TDS reading, below 50 parts per million (ppm), does not provide these necessary trace elements. Conversely, water with an excessively high TDS can lead to mineral buildup in the soil, which eventually hinders the plant’s ability to take up water and other nutrients.
Impact of Different Bottled Water Types
The wide variety of bottled water available means that each type has a unique impact on soil and plant health. Distilled and purified waters, which include those processed by reverse osmosis (RO), are defined by their ultra-low TDS, often reading near 0 ppm. This lack of dissolved minerals creates a problem for plant roots because it can cause a leaching effect. Over time, this “empty” water can actively pull existing nutrients out of the soil and potentially out of the plant’s roots, leading to long-term nutrient deficiencies if not supplemented with fertilizer.
Spring water, the most common type of bottled water, is generally a good option because it naturally contains varying levels of beneficial minerals. These minerals, like calcium and magnesium, contribute to healthy plant growth and soil structure. However, because spring water comes from diverse underground sources, its specific TDS and pH levels can fluctuate significantly depending on the bottling location. Its mineral consistency is not guaranteed.
Alkaline bottled water, which has a pH typically above 8.0, poses a different kind of risk to most plants. While the high pH is often marketed as beneficial for human consumption, it can cause a condition called “nutrient lockout” in the soil. When the soil environment becomes too alkaline, micronutrients like iron and manganese become chemically unavailable to the plant, even if they are present. This can result in chlorosis, a yellowing of the leaves that signals an inability to access necessary compounds.
When Tap Water is Problematic
Many people seek bottled water alternatives because municipal tap water can present specific challenges to plant care. One of the most common issues is hard water, which contains high concentrations of calcium and magnesium bicarbonates. When the water evaporates, these minerals remain in the soil, often forming a noticeable white or yellow crust on the soil surface and the rim of the pot. This mineral buildup can increase the soil’s pH over time, causing the same nutrient lockout issues associated with alkaline water.
Municipal water systems also use disinfectants, most commonly chlorine or chloramine, to ensure water safety. While established plants can usually tolerate the low concentrations of these chemicals, high levels can negatively affect the delicate microbial population in the soil. These beneficial microbes are responsible for breaking down organic matter and converting nutrients into forms that plant roots can absorb. The presence of chloramine, unlike chlorine, cannot be removed by simply letting the water sit out because it does not evaporate easily.
Another potential problem with tap water is a naturally high pH level, which is common in areas with limestone or chalk bedrock. For acid-loving plants, such as certain ferns, orchids, or azaleas, a high-pH water source can gradually compromise their health. Continual watering with alkaline tap water shifts the soil pH upwards, making it difficult for these sensitive species to absorb essential nutrients like iron, leading to stunted growth and leaf discoloration.
Practical Watering Recommendations
For the majority of hardy houseplants and garden plants, standard tap water is perfectly acceptable, especially if allowed to sit in an open container for 24 hours to dissipate any chlorine. This simple step is an easy way to improve water quality without resorting to bottled options. If you live in an area with particularly hard water, occasionally flushing the soil with a large volume of pure water can help remove accumulated mineral salts.
The expense of bottled or purified water is generally only justified for specific, sensitive plants that evolved in nutrient-poor environments. Carnivorous plants, such as Venus flytraps and pitcher plants, and delicate houseplants like Calatheas and Orchids, thrive best with distilled or reverse osmosis water. For these species, the ultra-low TDS prevents the leaf-tip burn and root damage caused by mineral salts.