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Preventing Fruit on Ornamental Plum Trees with Hormone Sprays

Chemical Thinning for Fruit Suppression

To stop an ornamental plum from fruiting, apply growth regulators shortly after petal fall. Two options:

Gibberellic acid (GA3) – spray ~1 week post petal fall.
Naphthalene acetic acid (NAA) – more complete thinning, same timing.

Both are plant hormones, not restricted-use pesticides. Apply a heavier concentration than for thinning to eliminate most fruit. Follow apple-thinning guidelines adapted for plums. Timing is critical: a narrow 2-week window at 65–95°F.

Trees: Premature Fruit Ripening and Drop in Plum Trees: Environmental Causes; Plum Tree with Jelly-Like Sap: Borer Infestation; Victoria Plum Maggots: Plum Moth, Preventive Spraying Required; Plum Curculio and Codling Moth Control on Fruit Trees: Spinosad Option; Growing Tropical Fruit Trees from Seed in Canada – Challenges; Stratifying Plum Seeds for Germination; Black Knot on Plum Trees: Fruit Safety and Disease Management; Preventing Fruit on Ornamental Plum Trees; Fruit Tree Selection for Central New Hampshire; Bark Loss on Ornamental Pear Trees in Cold Climates

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