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Glossary

Perlite

Expanded volcanic rock that aerates the substrate and prevents compact root balls.

1 min read

Perlite is those white balls that look like Styrofoam. They are not: it is expanded volcanic rock. Its job is to create air, not to provide nutrients.

Uses

Lightening universal soil, mixing with coconut, seedbeds, and cuttings. Water drains; roots breathe. In pots that are watered frequently, it is almost essential.

What it is not

It is not vermiculite (that retains more water and compresses). It is not clay pebbles (larger balls for bottom drainage). It is not edible and does not dissolve in watering.

Practical use

20-30% by volume in most mixes. Moisten it a bit to prevent it from flying around when mixing. It can be reused if screened and not from a sick plant.

What we recommend at Control Garden

Perlite in loose packs or combined with vermiculite and clay pebbles. The quick way if you don't want to buy three bags by eye.

Recommended products

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FAQs

Is it toxic?
It is inert. Avoid dust: moisten when mixing and do not breathe it in like flour.
Does it replace pot drainage?
No. Holes are still necessary. Perlite aerates the volume; the hole drains the water.
Does it float when watering?
A little, especially the first time. Mix it well, do not leave it on the surface as the only mulch.

Keep reading

All universes

Vermiculite

Expanded mineral that retains water and cations. Ideal for overly dry terraces.

Expanded Clay or Arlite

Lightweight expanded clay balls for drainage, hydroponics, and preventing waterlogged root balls.

Can perlite be reused?

Yes, if the plant was healthy. Sift, rinse, and mix with a bit of new.

Seedling Tray

Container and technique for germinating with moisture control and separated roots.