Vermiculite
Answered by: Conrad Richter
Question from: Ron
Posted on: March 31, 2009

I am surprised you suggest using vermiculite in your seed classes. Am I wrong or is this the stuff that is (or was) used to insulate homes, has caused cancer in humans?

Vermiculite sold by the W.R. Grace Company that came from its Libby, Montana, mine was found to be contaminated with asbestos. The company was later forced into bankruptcy when it was hit by fines and lawsuits. The contaminated vermiculite was sold up until the early 1990s. Since then all vermiculite mines are tested and only asbestos-free material is allowed to be sold.

Horticultural vermiculite is a fantastic soil conditioner. It promotes friability, drainage and aeration. We like to cover seeds with a fine grade vermiculite instead of typical sowing media because it does not impede seedling penetration during germination, yet it maintains a microclimate of high humidity around the seeds. And when it comes time to transplant, the seedlings separate easily with minimal disturbance to the root system.

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