Why Seedlings Die in the Greenhouse: Heat, Light, Water Balance

Sudden seedling collapse (impatiens, petunias, salvias) usually signals one of three deficits:

• Light: 12+ hours of strong light (sun or 40W fluorescents 3–4 inches above plants).
• Temperature: Steady 65–70°F.
• Water: Consistently moist but not soggy; never let dry out completely.

Check each factor. Leggy, pale seedlings need more light. Wilting despite wet soil indicates root rot from poor drainage or overwatering. Adjust conditions immediately.