You've tried water and soil, but have you ever rooted a cutting in a Fluval Stratum? Yes, it’s technically made for fish tanks. Yes, it looks like little black caviar. But it might just be the best thing to happen to your houseplant propagation. So in this episode, let’s break down everything I’ve learned from my conversation with my plant friend, Lindsay Sisti (@alltheplantbabies), who is a propagation extraordinaire and the author of The Ultimate Guide to Houseplant Propagation. Thanks to her, I now know exactly how and why this strange little volcanic material is revolutionizing plant propagation!

 

In this episode, we learn:

• [00:00] Is there a mess-free plant propagation?
• [02:28] How did Lindsay become a propagation expert?
• [07:31] What is hybridization/pollination of plants?
• [09:26] What is Fluval Stratum?
• [10:00] What is a volcanic tephra?
• [12:42] What makes Fluval Stratum popular for plant propagation?
• [14:47] Protect yourself this Melanoma Awareness Month with Coolibar’s sun-protective clothing!
• [19:07] LECA vs. Fluval Stratum
• [20:25] Practical tips for propagating with Fluval Stratum
• [25:10] Can you re-use Fluval Stratum?
• [26:49] What are the best plants for Fluval Stratum
• [27:53] Combining Fluval Stratum with perlite
• [30:50] Can Fluval Stratum be used as a growing medium in semi-hydroponic setups?
• [32:27] What are the best practices for propagating plant cuttings in Fluval Stratum?
• [34:52] Transferring cuttings from Fluval to potting media
• [36:50] Experiments with different growth mediums (Fluval Stratum, aroid mix, tree fern fiber, sphagnum moss, and peat moss)
• [39:58] Where can you find Lindsay and her resources online?

 

 

 

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What Is Fluval Stratum?

Fluval Stratum is made from volcanic tephra, which is the material released from volcanoes, such as ash or mineral-rich soil. This tephra comes from one single volcano in Japan — Mount Aso. That is so mystical to me.

This substrate looks like tiny black caviar beads and when you touch it, it feels soft, mushy, and squishy because it's actually compressed volcanic soil, not rock (but it has volcanic rock composition). Unlike something like LECA or perlite, Fluval Stratum breaks down over time. But that’s part of what makes it such a powerhouse.

Note: technically Fluval is a brand and the product is stratum.

 

 

Why Fluval Stratum Works

Fluval Stratum is so effective for propagation because it all comes down to its structure and chemistry. The little pellets create pockets of air between them, which is crucial for root health, and they’re porous, so they hold just the right amount of water.

Also, Stratum naturally buffers water to a slightly acidic pH, usually around 6 to 6.5, which is exactly what most aroids (and many houseplants) need to absorb nutrients efficiently.

And unlike water propagation, where you often get delicate, water-adapted roots, plants rooted in Stratum develop soil-style roots, which is sturdier, fuzzier, and more robust. This makes transplanting way easier and less prone to shock.

Did I mention it has natural trace minerals, including iron? Which is a micronutrient for plants and helps with chlorophyll production.

 

 

How to Propagate in Fluval Stratum (The Right Way)

I’ve now officially propagated Hoyas, philodendrons, and some Alocasia corms in Fluval Stratum. And Lindsay walked me through exactly how to do it right.

Here’s how you do it:

1. Grab a jar (mason jars are great; clear containers let you see root growth and monitor water levels).
2. Add 2 inches of Fluval Stratum to the bottom.
3. Place your cutting into the jar and fill around it with more Stratum.
4. Add enough water so that the bottom layer of Stratum stays wet (usually about 1 to 2 inches.)

That’s it! Just keep the bottom layer moist and never let it dry out (this is Lindsay’s golden rule). If you let Stratum dry out, it loses its magic. The roots will dry up, and your cutting may fail. So stay on top of your moisture, and your plants will grow.

 

 

Can You Reuse Fluval Stratum?

Yes! Unless your cutting had root rot or disease, you can absolutely rinse and reuse your Fluval Stratum.

Over time (usually around a year), they will begin to break down and get a bit muddy. When that happens, or if you start noticing algae buildup, it’s time to replace it.

I personally love that it’s reusable. Stratum isn’t the cheapest substrate, but you definitely get your money’s worth.

And pro tip: for large cuttings like Monstera or bigger aroids, Lindsay recommends mixing Stratum with perlite (50/50) to save on cost and still get all the benefits. That mix also increases airflow, which bigger plants love.

 

 

What Plants Work Best in Fluval Stratum?

Literally, everything.

Lindsay hasn’t met a houseplant yet that didn’t root successfully in Stratum. That includes pothos, Hoya, Monstera, Alocasia corms, even anthurium seeds (she did massive experiments comparing growth in Fluval Stratum vs. moss vs. soil, and Stratum won every time).

That said, Stratum isn’t a forever home. While you can leave a plant in it for a season (or longer if it’s growing), it’s really best as a propagation medium.

Once your roots hit around 2 inches and start to branch, that’s your cue to pot up in soil or another growing medium. And because the roots are already adapted to solid media, the transition is smoother than coming from water.

Lindsay even uses Stratum in semi-hydro setups, though she prefers LECA or Lechuza Pon for long-term growing, since Stratum breaks down over time.

 

 

Nerding Out in the Name of Joy

Massive thanks to Lindsay for opening my eyes to this amazing substrate! I know we’ve gone a bit nerdy in this episode talking about genealogy, hybridization, etc. Make sure to download Lindsay’s book for more tutorials for every propagation method under the sun!

Let me know if you try this method. I’d love to see your propagation jars!

 

 

Mentioned in our conversation:

• Get a copy of Lindsay’s book,  The Ultimate Guide to Houseplant Propagation
• Fluval Stratum
• LECA
• Lechuza Pon
• Hoya propagation tutorial with @alltheplantbabies

 

 

Thank you to our episode sponsor:

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