Vermiculite is an important ingredient of Mel’s Mix, the gardening soil I use in my square foot garden. It is particularly helpful for square foot, container, and raised bed gardens.
Some of the most common questions I get asked about vermiculite are:
- What is it?
- Where can I buy it?
- Is it safe?
- Are there any substitutes?
What is vermiculite?
Vermiculite is a natural mineral. It starts off like mica–sort of a flaky rock. When heat is applied, it expands and becomes a light, fluffy, fire-resistant material. There are numerous uses for this product (like insulation), but here we’re using it as a soil conditioner for our garden beds. It helps keep soil light, allows for good airflow, and absorbs and retains water. When added to compost and peat moss, it creates Mel’s Mix.
Where can I buy vermiculite?
Sometimes “box stores” like Wal-Mart, Home Depot, or Lowes will carry vermiculite. However, they tend to carry only small bags, and they are expensive. It’s better to get them in larger quantities (3 or 4 cubic foot bags), which can sometimes be found at local nurseries or farm co-op stores.
I was recently doing a web search on this, and hit the JACKPOT! Here is a link to a list of stores that carry vermiculite across the USA. Many thanks to the creator of this list!
Is vermiculite safe?
In the past, vermiculite was sometimes mined from the same location as asbestos, which is quite toxic and dangerous. It is possible that older vermiculite (like that you might find in attic or wall insulation) was contaminated. I am quite confident that the problem was identified, and the vermiculite currently sold in stores is safe. (I am not an expert–this is just my opinion.)
Are there substitutes for vermiculite?
If you simply cannot find vermiculite, you have an alternative. First, you can always garden with straight compost, or a mix of compost and peat moss. My experience is, this soil gets very bogged down with water, and doesn’t drain well. The other option is to purchase Perlite. This is the white stuff you find in potting mixes. It does not have all the great benefits of vermiculite, but will do in a pinch.