Pacific Crabapple

Walnut trees produce juglone, which is toxic to many fruit trees including apples, inhibiting their growth and potentially causing death.

Black walnut species produce juglone, which is toxic to many rosaceous plants including apples and crabapples, inhibiting their growth and potentially killing them.

Large oak trees create dense shade that suppresses understory fruit trees, and oak leaf litter contains tannins that can inhibit other plant growth.

Hackberry trees create dense shade that reduces fruit production in understory apple trees, while leaf litter may contain growth-inhibiting compounds.

Black walnuts produce juglone, a natural herbicide that is particularly harmful to apple trees and other members of the Rosaceae family.