Pumice

Pumice FAQ: Everything You Need to Know for Happy Plants

Pumice might just look like gravel, but for your houseplants, it can be a game-changer. It improves drainage, boosts airflow, and helps prevent root rot. Still, if you’ve never used it before, it’s normal to wonder: how much should I use? When is it better than perlite? What if I just want my plant to survive, not become a science project?

That’s why we created this FAQ — to answer everything you might wonder about pumice.

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General Questions

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What exactly is pumice?

It’s a porous volcanic rock formed when lava rapidly cools. It’s lightweight, full of air pockets, and naturally sterile — perfect for potting mixes.

Why do people use pumice for plants?

It:

  • Improves drainage
  • Boosts airflow to roots
  • Helps prevent overwatering and root rot
  • Doesn’t break down over time

How is pumice different from gravel?

Gravel is dense and non-porous — it doesn't improve aeration or hold moisture. Pumice is light, porous, and useful throughout the soil, not just at the bottom of the pot.

What is the difference between pumice and perlite for houseplants?

The main difference between pumice and perlite is that pumice is much heavier. It also holds onto more moisture and nutrients than perlite. It is better for mixes that need weight and good drainage, like cacti and succulent mixes.

What size pumice is best for plants?

  • Fine (1–4 mm): Seedlings, propagation, finer mixes
  • Medium (4–8 mm): Most houseplants, such as cacti, succulents, orchids
  • Coarse (8–16 mm): Plants with bigger roots, especially aroids

Is pumice safe for all plant types?

Mostly yes, but it’s not ideal as the main component for moisture-loving plants like ferns or calatheas. It works best when blended with coir or worm castings, such as our syngonium mix.

Why does the pumice come slightly moist?

Pumice has a natural moisture content. The moisture is necessary for good plant growth with this material. If the pumice is completely dry, it will no longer absorb water and can draw moisture from your plant's roots.

Does pumice contain nutrients?

No. It’s inert. It doesn't feed your plant but helps create better soil structure. Pair it with nutrient sources like worm castings or plant food.

Will pumice prevent fungus gnats?

It helps. Since pumice keeps the top layer dry and prevents soggy spots, it can reduce gnat infestations — especially when used as a top dressing.

What does pumice look like?

It’s usually light grey to reddish, with a rough, irregular texture full of air pockets. It looks like miniature lava stones — because it is.

Using Pumice in Potting Mixes

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What ratio of pumice should I use in soil?

  • 10–20% for general houseplants
  • 30–40% for succulents and cacti
  • 25–30% for aroids and orchids

How do I mix pumice into soil?

Use a clean container or tarp and blend it thoroughly with your other soil components. Mix well to avoid clumping or layering.

Can I use pumice in nursery pots?

Yes. It’s especially helpful in plastic nursery pots that don’t “breathe” well. It keeps roots from suffocating.

Can I use pumice as a top layer?

Definitely. A 1–2 cm layer helps reduce fungus gnats, and gives a tidy look.

Does pumice float in water?

No. Unlike perlite, pumice sinks — which helps keep your soil structure consistent over time.

Does pumice compact over time?

No. That’s one of its big advantages. It retains its shape and structure even after years of watering.

Can I add pumice to coco coir?

Yes — and it’s a great combo. Coir holds moisture well, and pumice balances it out by improving airflow and drainage.

Can I combine pumice with sand?

You can, but use sand sparingly — it can make soil too dense. Pumice offers similar drainage benefits without compaction. This is not great for most houseplants, but can be great for Lithops and Split rock succulents!

Can I use pumice for bonsai trees?

Yes. Many bonsai growers use pumice in custom mixes because it holds shape, drains well, and encourages fine root growth.

Plant-Specific Questions

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Which plants benefit most from pumice?

  • Cacti and succulents
  • Monstera, Philodendron, Syngonium
  • Orchids and Hoyas (instead of bark)
  • Snake plants and ZZ plants
  • Citrus trees (indoor or balcony)

Can I use pumice for herbs or edible plants?

Yes, but blend it with compost-rich soil. Herbs like rosemary or thyme (which dislike soggy roots) benefit most.

Is pumice useful for ferns?

In small amounts. Ferns like moisture, so use pumice only to lighten dense mixes — 10% max. Usually perlite will do the trick, so no pumice is needed!

Do carnivorous plants like pumice?

Generally no. Most carnivorous plants prefer nutrient-poor, acidic media like sphagnum moss or peat alternatives.

Can I use pumice for palms or citrus in containers?

Yes — especially for improving root health and preventing root rot in citrus and potted palm species.

Pumice in Hydroponics and Propagation

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Can I use pumice for semi-hydroponics?

 Yes, but it behaves differently than clay balls:

  • Holds more moisture
  • Doesn’t float
  • Better suited for passive hydro setups, like wick systems
  • Mix with lava stones and zeolite for a great balance in aeration and water supply

Can I root cuttings in pumice?

Yes. Just place the cutting in damp pumice and keep it moist. It offers excellent airflow and light support for fragile roots.

Can I grow plants fully in pumice without soil?

You can for some plants — especially succulents or slow-growing semi-hydro plants. But you’ll need to supplement nutrients.

How often should I water when using lots of pumice?

More often. Pumice drains quickly and doesn’t hold water like peat or coco coir. Always monitor your plant’s needs.

Cleaning, Reusing and Storing

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How do I clean used pumice?

  • Soak in water with a bit of vinegar or hydrogen peroxide
  • Rinse thoroughly
  • Let it dry fully before reusing

Do I need to sterilize pumice between uses?

It’s not required, but recommended if the previous plant had pests, fungus, or rot.

Can I bake pumice to sterilize it?

Yes — spread it on a baking tray and heat it at 150°C for 30 minutes. Let it cool before using.

Does pumice go bad?

No. It’s rock. It can last decades if stored properly.

Can I store pumice outdoors?

Yes — just make sure it’s in a dry place, away from direct rainfall to avoid algae or moss growing on it.

Product-Specific (Sybotanica)

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What makes Sybotanica pumice different?

  • Mined sustainably in Germany
  • Washed and ready to use
  • Packed by hand in the Netherlands
  • No artificial fillers or additives

What size bags do you sell?

We offer 1L, 3L, and 20L sizes, depending on your project. See our Pumice product page for options.

Can I combine your pumice with other Sybotanica products?

 Yes — it pairs especially well with:

Do you offer pre-mixed soil with pumice included?

Yes — see our cactus and succulent mix, bonsai mix and syngonium mix. Each includes pumice in the perfect ratio for its plant type.

Advanced and Niche Questions

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Is pumice environmentally friendly?

Yes, especially if it’s sourced locally. It doesn’t release harmful byproducts, and it lasts for years.

Can pumice cause salt build-up?

No, but over time, salts from water or fertilizer may collect on the rocks. Rinse or flush your pot to remove buildup.

Will pumice absorb fertilizer?

Pumice retains some nutrients in its pores but doesn’t store them the way organic matter does. You still need regular feeding.

Can I use pumice in terrariums?

Yes, but in small amounts. Use it as a drainage layer or mixed into soil — it prevents rot in closed environments.

Can I use pumice for air-layering or moss poles?

It’s not ideal for air-layering. For moss poles, you can mix pumice into the base soil for added drainage and to stabilize the pole — but don’t pack it into the whole pole, just the bottom.

Is pumice fire-safe or heat resistant?

Yes. It’s a volcanic rock and can handle extreme temperatures — just don’t use it as a substitute for BBQ stones.

Want to know even more about Sybotanica's pumice?

Check out our pumice product page or read more here.