White Powder and Chemical Smell in Raised Bed: Fungus or Stump Decay?

After removing an arborvitae, a gardener found white, powdery, chemically-smelling material deep in the raised bed soil, mainly around old roots. Concerns: mildew, drainage, stump interference.

Expert Assessment

• White powder is likely fungus—some decompose organic matter; some are beneficial mycorrhizae. Not alarming.
• Green stump robs nitrogen as it decays. Fertilize nearby plants with foliar feeds for the first year.
• Bagged garden soil in elevated beds drains too fast, dries unevenly, increases winter kill risk.
• Better mix: 2/3 garden clay + 1/3 coarse organic matter (bark, compost). For annuals/perennials needing sharp drainage, 1/2 and 1/2.
• No plastic barrier needed. Remove as much stump as practical.

Blend clay into your bed soil for better water/nutrient retention and plant performance.