Perlite or Vermiculite? – Backyard Food Growing

How do you choose which one to use? 

For Drainage: Choose perlite
For Water Retention: Choose vermiculite

For planters, I suggest using a little of each as they have complimentary properties.

The ratio should be 25% of one or both of these total to potting soil. So that means ¾ of the volume of potting soil and the rest (¼ of the volume) can be any balance of perlite and/or vermiculite.

Perlite

  • white granular particles
  • a form of volcanic glass
  • containing about 6% water
  • neutral pH
  • surface area of the particles are covered with little indents that hold nutrients and water
  • clean, odourless, sterile and non-toxic
  • will not rot or mold
  • better for drainage than vermiculite
  • lightweight substitute for sand
  • can float to the top of potted plants due to its light weight
  • holds 3-4 times it’s weight in water

Vermiculite

  • silicate mineral resembling mica, the colour can vary
  • retain moisture and plant nutrients
  • mixes well with soil
  • clean, sterile, odourless, non-toxic
  • cheaper than perlite
  • contains trace minerals
  • retains water, air and nutrients
  • not as durable as perlite
  • can trap too much water causing soggy, mucky soil

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