gloxinia

Cause

Gloxinia's broad, velvety, downy leaves are adapted to bright but filtered light under a greenhouse bench, and when placed in direct sun the foliage is sunscalded — the upper surface of the leaf bleaches, yellows, and browns where ultraviolet intensity exceeds what the thin leaf tissue can dissipate.

Solutions

• Move the plant into bright light that is filtered by a sheer curtain or into a spot that receives morning sun only, so the leaves are never lit by harsh midday rays.
• Pair the move with steady warmth and a moist atmosphere, since gloxinias require a warm, moist environment during growth and blooming to recover from leaf scorch.
• Mist around the plant rather than over the foliage, and water only from beneath so the leaves stay dry while humidity around the pot rises.

Cause

Gloxinia (Sinningia speciosa) grows from a tuber that sits in constantly damp soil, and excess moisture around the tuber and crown is the leading cause of rot; the same soil that holds the velvety leaves upright when correctly moist becomes waterlogged when watered too often or with cold water, suffocating the roots and turning the tuber soft.

Solutions

• Test the soil by squeezing a handful into a ball — if it falls apart when touched, water is needed; otherwise leave it alone, because gloxinias depend more on proper watering than on any other single factor.
• Start the dormant tuber in vermiculite rather than wet potting soil to avoid rot, then shift it into regular potting mix in at least a 5-inch pot once new growth is established, handling new roots quickly and gently.
• Always water from below by standing the pot in a bowl of tepid water until the surface of the soil becomes moist, then remove and let it drain so no water falls on the large, hairy leaves.