Crushed, Washed, Screened Granite

Heinz Grotzke writes in Biodynamic Greenhouse Management: “The best addition to the soil blend is granite crushed to the size of river sand or somewhat larger. For root growth the particle shape is an important factor. A crushed screened rock has sharp and irregular edges—a physical advantage for both drainage and root formation, especially in the development of secondary roots as they occur on cuttings and young seedlings.” Heinz also emphasizes the value of material with “fresh edges” from the bedrock, for its silica content and its formative influences. We are fortunate to have a major granite quarry just down the road from us, and this manufactured sand is made to our specifications.