Why Grass Won't Grow Under Pecan Trees: Juglone Toxicity Explained

Pecan Trees and Lawn Failure: The Juglone Connection

A homeowner in Thrall, Texas, struggles with a yard that was once green but is now dirt, rocks, and pecans. Despite fertilizing (with ant-killer blend), grass refuses to grow. The answer may lie in the pecan trees themselves.

Allelopathy and Juglones

Pecan trees (Carya illinoensis) and their relatives—black walnut, butternut, and hickory—produce juglones, toxic compounds that inhibit growth of many plants. This phenomenon, called allelopathy, creates a zone around the tree where most groundcovers and grasses fail. Juglones shut down respiration in sensitive plants, causing wilting, yellowing, or odd growth patterns.

What to Consider

• Are there pecan trees currently or previously on the site?
• What grass species are you trying to grow?
• What are the sun, water, and soil conditions beyond juglone presence?

Some plants tolerate juglones, but most turfgrasses struggle. If pecan trees are the cause, options include selecting juglone-tolerant grasses, using raised beds with imported soil, or converting the area to mulch and shade-tolerant groundcovers.