Why my plum tree blossoms but the flowers fall without setting fruit and what to do

What's happening

It's common to see plum trees with pretty flowers that, after a while, wither and fall without forming fruit. This is known as flower abortion or fruit set failure. In your case there are also leaves with brown/reddish spots, indicative of mild foliar stress or superficial attacks that reduce vigor, although there are no signs of widespread rot.

Most likely causes

• Insufficient pollination: few bees or cold/rainy days during flowering prevent pollen transfer.
• Water stress: drought or irregular irrigation during flowering and early fruit set prevents the fruit from forming.
• Damage from late frost or abrupt temperature fluctuations during flowering.
• Mild foliar pests or diseases (spots, aphids, mites) that weaken the plant.
• Moderate nutrient deficiency (e.g., lack of boron or nitrogen imbalance) that hinders fertilization or early fruit development.

What to do: practical measures

Here are concrete and easy-to-apply actions to improve fruit set and tree health.

1. Improve pollination

• Attract nearby pollinators: plant flowers such as lavender, rosemary, clover, or wildflower species that favor bees and other insects.
• Avoid insecticides during flowering: chemical products kill bees and reduce pollination.
• Manual pollination: if there are not enough bees, use a soft brush or small paintbrush and transfer pollen between flowers on sunny days (better in the morning).

2. Proper watering

• Maintain even soil moisture during the 2–3 weeks before and after flowering: deep, spaced irrigations rather than frequent shallow waterings.
• Avoid waterlogging: excess water also stresses the roots.
• Water in the morning and at ground level to reduce evaporation loss and nighttime stress.

3. Protection against cold

• If there is a risk of nighttime frosts during flowering, cover the tree during critical hours with frost cloths or breathable plastic to gain a few degrees.
• Remove covers during the day to avoid overheating and condensation.

4. Control of foliar pests and diseases

• Inspect leaves and shoots every 7–14 days for aphids, mites, or increasing spots.
• Manually remove heavily affected leaves and prune branches with visible damage.
• Mild treatments: potassium soap or summer oil are effective and less harmful to pollinators; apply them outside flowering and according to instructions.

5. Nutritional adjustments

• Apply a balanced fruit-tree fertilizer or organic manure in spring (well-composted manure, compost) to restore vigor.
• If you suspect boron deficiency (especially if widespread flower abortion is observed), consult local recommendations and perform a specific, dosed foliar application; do not use high doses without testing.
• Avoid heavy nitrogen fertilization during flowering that promotes vegetative growth at the expense of fruit set.

Checklist for 7–14 days

• Do signs of fruit set (small fruits) appear after encouraging pollination?
• Do foliar spots remain stable or increase? Remove very damaged leaves.
• Is soil moisture in the top 2–3 cm adequate? Adjust irrigation if it is very dry or waterlogged.
• Have nighttime temperatures dropped below tolerable levels? Protect on future cold nights.

Conclusion

Flower drop in plum trees is usually the result of several combined factors: insufficient pollination, water stress, cold, or mild nutritional and foliar problems. Addressing each point with simple measures — attract pollinators, regular watering, protect from cold, monitor pests, and adjust fertilization — will greatly increase the chances that flowers set and produce fruit. If, despite these measures, the problem persists or foliar spots spread, consult a local technician for more specific analyses.