Osmosis water

Osmosis water – why it is so relevant for anthuriums

Anyone cultivating rare or sensitive anthuriums will sooner or later encounter a crucial issue: water quality. Besides light, humidity, and substrate, the irrigation water is particularly important for root health, leaf quality, and consistent growth. A frequently recommended solution: reverse osmosis water.

But what exactly does that mean – and is it really beneficial for anthuriums?

Definition: What is reverse osmosis water?
Osmosis water (also known as reverse osmosis water or RO water) is tap water that has been filtered through several special membranes. This process removes almost all dissolved substances.

  • Calcium (Ca)
  • Magnesium (Mg)
  • Sodium (Na)
  • Carbonates
  • Heavy metals
  • chlorine
  • Salts

What remains is extremely soft, almost mineral-free water with a very low conductivity.

What is the pH value of reverse osmosis water?

Freshly filtered reverse osmosis water usually has a pH value of around 6.5–7.0. However, since it lacks carbonate hardness (KH), it lacks buffering capacity. As soon as the water comes into contact with air, CO₂ dissolves and the pH value can drop to about 5.5–6.5.

Important for anthuriums:

  • The pH value of pure reverse osmosis water is not stable.
  • Only by mixing it with fertilizer does a controllable nutrient solution result.
  • The target range for many anthuriums is a pH value of 5.5–6.2 in the irrigation water.

Why are anthuriums sensitive to tap water?

Many anthuriums originate from tropical regions of Central and South America. There they grow:

  • epiphytic or semi-epiphytic
  • in loose, organic material
  • with very soft rainwater
  • at consistently low salt load

Hard tap water can lead to problems in the long term:

  • Salt accumulation in the substrate
  • impaired nutrient absorption
  • blocked trace elements
  • Root damage

This is often first evident in sensitive anthuriums through:

  • matte, smaller leaves
  • Burnt leaf tips
  • slowed growth
  • Root decline

Advantages of reverse osmosis water for anthuriums:

  • Minimal salt exposure: Reduces the risk of root damage and salt stress.
  • Full control over EC and nutrient profile: You determine exactly how much calcium, magnesium or nitrogen your plant receives.
  • Adjustable, stable target pH value. Ideal for slightly acidic conditions, which are preferred by anthuriums.
  • Reduced substrate acidification due to carbonates
  • Clean leaf surfaces
  • No limescale stains on dark, velvety leaves
  • More consistent results in sensitive species

Possible disadvantages:

  • Contains no minerals: Without targeted fertilization, calcium or magnesium deficiencies quickly develop.
  • No buffering capacity: The pH value in the substrate can fluctuate more quickly.
  • Technical effort and acquisition costs
  • Not absolutely necessary with very soft tap water

Practical recommendation for anthuriums

Many experienced collectors work with a mixture of:

  • 50–100% reverse osmosis water
  • targeted Cal-Mag supplementation
  • weakly dosed, but regular fertilization
  • EC control (often in the range of 0.6–1.2 mS/cm depending on the stage)

What matters is not so much the pure water, but its consistency.

Conclusion

While reverse osmosis water is not essential for anthuriums, it is a very useful tool.
Those who cultivate rare, sensitive, or high-priced plants and value:

  • stable root health
  • controlled growth
  • optimal nutrient absorption

The system benefits significantly from the mineral-poor base.

In short:

Osmosis water creates controllable conditions.
And with anthuriums, control is often the difference between "survived" and "perfectly grown".