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Grass Dies Under Pecan Tree: Juglone Toxicity Explained

The Hidden Culprit: Juglone

Pecans (Carya illinoensis) are in the Juglandaceae family—same as black walnut. They produce juglone, a natural herbicide that inhibits many plants, including Bermuda and St. Augustine. Kentucky bluegrass tolerates it.

Why Now?

Tree matured; juglone output increased.
One grass species dominated, more sensitive.
Drought stress amplified toxicity.

Solutions

Best: Replace grass under dripline with juglone-tolerant ground covers (list at greenwoodnursery.com/page.cfm/27196).
If keeping grass: Apply slow-release organic nitrogen (blood meal, aged manure, Milorganite) spring/fall. Avoid fish emulsion—smell lingers.
Mulch heavily: 3–4 inches wood chips reduce root competition.

Don’t Fertilize the Pecan

Mature pecans need massive nitrogen—fertilizing grass just feeds the tree more. Focus on ground covers or accept the shade/root zone as a planting bed.

Lawns: Groundcover Solutions Under Pine Trees and Along Driveways; Growing Ground Cover Under Mature Maple Trees: Solutions for Shade and Root Competition; Grass Won't Grow Under Maple: Shade and Root Competition; Avocado Tree Shade and Grass: Don't Plant Under Canopy; Ground Cover Alternatives for Shady, High-Traffic Areas Under Trees; Why Grass Fails Under Oak Trees and What to Plant Instead; Pecan Tree Allelopathy: Why Grass Dies Under Juglone-Producing Trees; Why Grass Won't Grow After Tree Removal: Dealing with Decaying Roots; St. Augustine Dies in Circle Under Live Oak: Shade or Roots?; Growing St. Augustine Grass Under Trees: Shade Solutions and Watering Strategies

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