Overwintering Dipladenia Indoors with Grow Lights

Bringing a dipladenia (Mandevilla) indoors for winter doesn't mean it must go dormant—especially if you have grow lights. A gardener successfully controlled scale with alcohol swabs and pyrethrum spray but struggled with persistent black spots and leaf drop, despite the plant blooming under halide and sulfur grow lights.

Black Spot Treatment Options

Darlene offers two effective, accessible treatments for fungal black spot:

• Aerosol Lysol spray: Lightly spray fronts and backs of all leaves every 3–4 days until spots disappear. Proven effective on houseplants.
• Baking soda solution: Mix baking soda in water, spray thoroughly on all leaf surfaces. A known remedy for roses, though it leaves a temporary white haze.

Winter Care Under Lights

Since the grow lights provide longer "days" than nights, treat the plant as if it's summer: water normally, fertilize regularly, and maintain active growth. Cooler temperatures (but above 50°F) can actually promote healthier recovery.

With consistent treatment and proper lighting, your dipladenia can stay vibrant all winter—no dormancy required.