Calathea 'Mia' Leaf Cycle: A Genetic Trait, Not a Care Failure

Your Calathea 'Mia' plants are thriving—lush foliage, minimal browning, even a long-lasting flower—yet they fold leaves at 5–6 PM and reopen around 3–4 AM, regardless of light adjustments. This is a genetic characteristic of the hybrid.

Why Hybrids Behave Differently

Calathea 'Mia' was bred for its unusual flower, potentially at the expense of typical nyctinastic rhythms. Not all calatheas exhibit strong leaf folding; those that do may have shifted cycles.

What You've Confirmed

• Altering light duration/timing doesn't shift the cycle.
• Removing ambient nightlight has no effect.
• Plants are otherwise healthy under your 16-hour artificial light regimen.

Bottom Line

Your care is exemplary. The plants have "decided" on a 14-hour open/10-hour closed cycle. Enjoy their health and unique personality—no intervention needed.