Lee Reich, AP 9:02 p.m. PST December 17, 2014
Rumor has it that mulching your garden beds or trees and shrubs could starve your plants. It’s a rumor that has circulated for the past 40 years or so, ever since mulching surged in popularity as a way to quell weeds and conserve water.
Is there anything to it? If anything, you’d think that nutrients in mulches would help nourish plants, not starve them.
The logic behind the starvation rumor goes like this: The two nutrients most needed by soil microorganisms are carbon and nitrogen. Wood chips, straw, sawdust and many other organic mulches are high in carbon but low in nitrogen. When soil microorganisms chew away on such mulches, decomposing them, they have to balance their carbon-rich diet with extra nitrogen, which they must find somewhere else. So they pull this nitrogen from the soil, and are a lot better than plants at getting it. The result: plants starved of nitrogen.