Rock dust for urban farmers


Portland organic fertilizer company Concentrates specializes in the growing industry of urban farming.

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Portland store Concentrates says it is the biggest distributor of organic fertilizer on the West Coast.

Portland’s urban farmers go to Concentrates to buy ingredients, including “glacial rock dust,” to make their own fertilizer for rooftop or indoor crops.

Most Portlanders aren’t aware of it, but Concentrates describes itself as the largest organic fertilizer distributor on the West Coast, driven by sales of its Gaia Green glacial rock dust, which have more than tripled in the past five years, owner Bill Sparks says. In the past year, he’s sold 151 tons of the dust, a natural byproduct of ancient glacial moraine rocks mined in coastal southwestern British Columbia.

Concentrates is no secret among the professional urban farmers who grow the toothsome vegetables, herbs and fruits that Portlanders relish in locavore-inflected restaurants such as Noble Rot and Meriwether’s. Marc Boucher-Colbert, who farms the pioneering rooftop food garden for Noble Rot, says he uses about 100 pounds of glacial rock dust a year from Concentrates. He believes its array of 67 minerals helps plants grow more vigorously, perhaps more nutritiously, and stand up better to frost, extending his growing season.

Read more at Willamette Week.

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