Perlite pH Concerns: Test Your Source Before Limiting Use

Jason read in The Savage Garden that perlite can be alkaline, recommending ≤20% in mixes. He uses >50% for drainage and cooling and asked for the nursery's take.

Source Matters

Perlite pH depends on the parent rock and manufacturing. Pacific Northwest perlite (from igneous rock) tests neutral. Arizona sources may differ. Test yours: soak perlite 24 hours in distilled/RO water, then measure pH. If ≤7, no restriction needed. If >7, limit to 20% as Peter D'Amato advises.