Growing plants in semi-hydro systems: a complete guide for houseplants

Jul 24, 2025 | 0 comments posted by Adrien SAINT

Semi-hydro culture / PON

Semi-hydroponic (or semi-hydro) gardening is becoming increasingly popular. Easy to set up and ideal for many tropical species such as Alocasia , Philodendron , Hoya , and Anthurium , this method relies on a soilless system in which the roots are partially submerged in a nutrient solution. Here's everything you need to know to start (or optimize) semi-hydro gardening.

Note that PON is a brand of Lechuza, and for example, at Studio Plantes, other manufacturers are chosen for their reservoir pots and for the substrate itself.

Materials needed

- A self-watering pot, preferably with a water level indicator

- The substrate, made of volcanic rocks

- A healthy plant, ideally without emerging leaves during the soil-to-semi-hydro transition

- A complete mineral fertilizer (NPK + trace elements).

- Recommended: a pH tester and possibly an EC (electrical conductivity) tester.

Why switch to semi-hydro?

- Better root aeration , limits the risk of rot.

- Less frequent and more predictable watering : the water level is easy to monitor.

- Total control of nutrition : every intake is controlled.

- Fewer soil pests (fungus gnats and others)

Water and nutrients: pH and EC

The ideal pH

- Target pH: 5.5 to 6.2 (you can usually check the water quality in your municipality online)

- Why? A slightly acidic pH promotes better nutrient absorption.

- To adjust the pH, there are products available to raise or lower it (see Hydropassion products for example)

EC (electrical conductivity) or nutrient concentration

EC recommended:

- Young or fragile plants: 0.6–1 mS/cm

- Established or very large plants: 1–2 mS/cm

- Excess EC can burn the roots, so be careful

- You can measure the EC of your solution using a tester

Fertilizer selection

- Use a 100% mineral fertilizer, this type of fertilizer is available at Studio Plantes, and can also be used for growing in soil.

- Alternate with watering with plain water every 2 to 4 weeks to avoid the accumulation of salts.

Maintenance frequency

- Monitor the nutrient solution level (do not exceed 1/3 of the pot).

- Change the solution completely every 2 to 3 waterings.

- Rinse the substrate regularly to avoid limescale deposits or algae.

- Monitor your room temperature to keep it above 19 degrees.

The transition to semi-hydropower

If you are converting a plant that is already in soil:

1. Carefully remove it from its pot, then clean its roots with lukewarm water to remove all traces of organic substrate.

2. Place the plant in the pre-rinsed semi-hydro substrate.

3. Introduce the nutrient solution gradually.

Tips to avoid mistakes

- Don't flood the system: The water should not reach all the roots at first.

- Never use organic fertilizer (risk of rot).

- Beware of excessively low temperatures: roots are more sensitive in water.

- Do a test first to see if this growing method suits you; don't start with your most prized plant.

In summary

Semi-hydro is a reliable, clean, and precise method for growing houseplants, provided that:

- Properly manage nutrition (pH and EC)

- Choosing the right equipment,

- Be patient during the transition phase; it remains a stress for the plant, so prioritize a transition when the plant is healthy.

You can find substrates, self-watering pots, and suitable fertilizers in the accessories section of the website: https://studio-plantes.com/collections/accessoires-terreaux