Chlorotic Grass at Downspouts: Roof Runoff Toxicity

NJ shore community. Kentucky bluegrass sod on sand. Grass at rain downspouts turns yellow and dies, spreading along water flow path. Multiple homes affected. Association can't identify cause.

Strong Evidence: Water-Borne Contaminant

Pattern follows roof runoff. Same problem at multiple homes = systemic source.

Likely Culprits

1. Roofing materials: Asphalt shingles, metal flashing, algae/moss treatments leach zinc, copper, hydrocarbons.
2. Gutter/downspout materials: Galvanized steel, copper, aluminum corrosion products.
3. Atmospheric deposition: Pollutants concentrated on roof, flushed by rain.

Diagnostic Steps

1. Collect runoff water during rain; send for lab analysis (metals, pH, organics).
2. Test soil at affected vs. unaffected areas (pH, EC, metals).
3. Check if problem started after roof replacement/gutter work.

Mitigation

• Extend downspouts away from lawn (buried drain pipe to street/storm drain).
• Install rain barrels with overflow diversion.
• Create gravel/rock drainage swale at downspout outlets.
• If soil contaminated: remove/replace top 6–12 inches in affected bands.

Grass Selection

Salt-tolerant grasses (alkaligrass, seashore paspalum) may survive better, but fixing the water source is the real solution.