Pecan Tree Allelopathy: Why Grass Dies Under Juglone-Producing Trees

DFW homeowner: Mature pecan tree, St. Augustine grass dying only near tree despite irrigation and sun.

Cause: Allelopathic Juglones

Pecans (Carya illinoensis) and relatives (black walnut, butternut, hickory) produce juglones—toxic compounds that inhibit respiration in susceptible plants. Roots "ooze" juglones within dripline.

Juglone-Tolerant Plants

• Fescue, Kentucky bluegrass, orchard grass, timothy, wheat
• White clover
• Other tolerant groundcovers

What Doesn't Work

More water won't help. Juglones persist in soil. Grass species selection is the only solution.

Action

Overseed/just transition to juglone-tolerant grass (fescue or KBG) under tree. Accept that St. Augustine cannot survive there. The tree is valuable—work with its chemistry.