Lechuza PON: How to Switch Plants Without Root Rot

Lechuza PON is a purely mineral substrate (pumice, lava and zeolite with a slow-release fertilizer) that you can use instead of potting soil, either in LECHUZA’s self-watering planters or in ordinary pots. Moving a plant into PON goes best when you follow LECHUZA’s planting instructions: you don’t need to strip all the soil off the roots, and for the first 12 weeks you water from the top with as little water as possible in the reservoir. Most PON root rot comes from keeping the bottom of the pot wet before roots can use that water.

Source: LECHUZA-PON product information, planting instructions and FAQ; LECHUZA CACTUSPON product page.

What Causes Root Rot in Lechuza PON?

The same thing that causes it in soil: roots sitting in wet substrate without enough air, which favors root rot organisms such as Pythium. The UC Statewide IPM Program explains that Pythium thrives under wet conditions brought about by poor drainage or excess irrigation, attacks young root tips first, and causes a brown to black root rot that can lead to wilting and collapse; its control advice centres on good drainage and water management.

In PON the usual trigger is the reservoir. Filled too early, it keeps the lower part of the pot wet while the roots are still up in the old root ball and cannot use that water. That is exactly why LECHUZA says to keep the reservoir as empty as possible for the first 12 weeks. Warning signs:

• A sour or rotten-egg smell from the pot.
• Wilting or yellowing even though the substrate is wet.
• Roots that are brown or black and soft instead of firm.

If you see these, empty the reservoir, let the pot dry out, and check the roots. Cut away rotten roots back to firm tissue and go back to top-watering. Our Pythium root rot guide covers this in detail.

PON on Its Own or Mixed?

LECHUZA sells PON as a complete substrate that replaces potting soil and clay granules, with a 2 to 5 mm particle size, high drainage capacity and a structure that does not compact. Used with its watering instructions, you don’t need to add anything to it.

Some growers add coarser material such as larger pumice or perlite for plants that like an especially airy root zone, or for pots where they want the substrate to dry faster. That is a matter of preference; there is no published research on ideal PON mixes for houseplants, so treat specific “best ratio” claims with caution. If you go this way, keep any additions mineral. LECHUZA also says PON can be mixed with potting soil, recommending its unfertilized BASICPON or MONOPON for loosening soil mixes. For cacti and succulents, LECHUZA sells CACTUSPON, a finer, especially free-draining blend with humus granules.

Clay pebbles (LECA) behave differently: they are larger and wick water upward less, which is why LECA setups usually rely on a water level kept low in the pot. See our hydroponics and hydroponic systems guides for other water-based setups.

Soil Roots vs Water Roots: What Is Known

Semi-hydro forums often say “soil roots” must die and be replaced by “water roots” before a plant can live in a mineral substrate. Roots do change with their environment, and roots that grow in waterlogged conditions can develop more internal air space. But there is little research on how houseplants such as Monstera, Philodendron or pothos adjust when moved from soil into PON, and no reliable figures for how much of the root system dies. In practice, with LECHUZA’s method the plant keeps its root ball and grows new roots out into the PON while you water from the top, so a dramatic root “conversion” is not something you have to manage.

How to Transition Plants to Lechuza PON

These are LECHUZA’s planting steps for its self-watering planters:

1. Prepare the planter. Place the irrigation layer that comes with the planter on the divider (it moves water up from the reservoir and prevents waterlogging), then add a thin layer of PON so the plant will sit at the right height.
2. Set the plant. Place it in the planter as usual. You don’t need to completely remove the soil from the roots.
3. Fill. Fill the planter completely with PON around the root ball.
4. Weeks 1 to 12: water from above. Water only as much as the plant can absorb and keep as little water as possible in the reservoir.
5. After 12 weeks: water through the water shaft. In a pot without the irrigation system, keep watering from above.

Spring and summer, when plants are growing actively, are the easiest times to repot. For a worked example, see our step-by-step guide to moving a Monstera into Lechuza PON.

Do You Need a “Bridge” Substrate?

Some online guides recommend moving plants through an intermediate substrate, such as an aquarium soil, for several weeks before PON. There is no evidence this improves results, and it means repotting the plant two or three times, which is stressful in itself. LECHUZA’s instructions go straight from the old root ball into PON. For a delicate plant, the better safeguards are repotting during active growth, keeping it out of direct sun for a few weeks, and being strict about top-watering only during the first 12 weeks.

Looking After Plants in PON

• Watering: LECHUZA says PON holds water well, so plants need watering less often. Judge it with a finger test, the PON watering indicator, or the planter’s water level indicator.
• Reservoir rhythm: after the 12-week phase, fill through the shaft and let the reservoir run empty, with a few dry days, before refilling, rather than keeping it constantly topped up. See our guide to self-watering pot problems.
• Feeding: PON is pre-fertilized for about 6 months. After that, LECHUZA recommends its liquid or slow-release fertilizers; any balanced houseplant fertilizer at label rate works. Feed less in winter.
• Salt build-up: fertilizer salts can collect in any container. Water thoroughly from the top now and then, letting the excess drain, and watch for a white crust on the surface; our guide to white crust on houseplant soil explains it.
• Repotting: PON does not break down like soil, and LECHUZA lists it as reusable; rinse it before using it again.

Is Lechuza PON Safe for Pets?

PON is a mineral substrate, and the ASPCA’s plant database covers plants, not substrates, so there is no ASPCA rating for it. It is not food: a pet that eats a lot of any potting material can get a stomach upset or worse, so stop diggers and chewers getting at it. More important is the plant itself: a pothos or Monstera in PON is just as toxic as in soil. Check your plant in our cat-safe plants guide or the ASPCA plant list.

Frequently Asked Questions

Are there any plants that can’t be in Lechuza PON?

LECHUZA describes LECHUZA-PON as suitable for all houseplants, but it sells CACTUSPON, a finer and especially free-draining blend, for cacti and succulents. Plants that need constantly moist, rich soil may need closer watering in a purely mineral mix.

Do I need to remove all the soil before planting in PON?

No. LECHUZA’s planting instructions say you don’t need to completely remove the soil from the roots.

When can I use the reservoir after planting in PON?

After 12 weeks. Until then LECHUZA says to water from above and keep as little water as possible in the reservoir.

Does Lechuza PON contain fertilizer?

Yes. It is pre-fertilized for about 6 months; after that, feed with a liquid or slow-release fertilizer.

Why does my plant in PON smell sour?

Usually the bottom of the pot has stayed wet without air, often from filling the reservoir too soon or too often. Empty the reservoir, let it dry, check the roots for rot, and go back to top-watering until the plant recovers.

Can I mix PON with potting soil?

Yes. LECHUZA says PON can be mixed with potting soil and recommends its unfertilized BASICPON or MONOPON for loosening soil mixes.