Mandevilla (Dipladenia) Leaf Yellowing: Light and Water Fixes

Jeff's two pink mandevillas flowered beautifully indoors but developed brown spots, yellow leaves, and leaf drop near a slider door with indirect light.

Diagnosis: Not Blight

Likely causes: insufficient light and improper watering.

Mandevilla Requirements

• Direct sun indoors – right in front of sunniest window.
• Even moisture in summer; allow slight drying in winter.
• Tight pot – repot only if extremely potbound (spring).
• Cool temps (60–70°F) – cool in summer, warm in winter.
• Winter humidity boost beneficial.
• Fertilize summer only.
• Prune after flowering – flowers form on previous year's growth.
• Watch for spider mites & mealybugs.
• White sap irritates skin/eyes.
• Propagate: 4-inch cuttings, overnight hardening.

Move to direct sun, adjust watering, and new growth should be healthy.