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Night lighting (photoperiod manipulation) in chrysanthemum

Night lighting in chrysanthemum is the application of a short, low-intensity light interruption during the dark period to delay flowering by maintaining the plant in its vegetative phase. The technique is the principal tool used by commercial floriculturists to time chrysanthemum blooms to festival market peaks.

Principle

Chrysanthemum is a qualitative short-day plant — it initiates flower buds only when the uninterrupted night period exceeds a critical length. The plant senses night length through phytochrome: brief exposure to red-rich light during the night converts the inactive Pr form to the active Pfr form, mimicking daytime. A 4-5 hour night-break therefore resets the plant's perception of night length, keeping it vegetative even when the natural day is short.

Implementation

Commercial growers apply 4-5 hours of low-intensity red-rich light (incandescent bulbs at approximately 100 lux at plant height, or red LEDs) for roughly 40 nights during the vegetative phase. The lighting is then withdrawn to allow flower-bud initiation and bloom to coincide with festival peaks such as Vinayaka Chavithi, Bathukamma, Dasara or Diwali. Far-red and pure blue light are far less effective for night break; the response is mediated specifically by the phytochrome Pr-to-Pfr conversion.

Adoption context

The technique is standard practice in commercial chrysanthemum production across South India — Karnataka (Doddaballapur), Tamil Nadu (Hosur), Andhra Pradesh (Kadiyam) — and in protected-cultivation polyhouse production for the cut-flower export market. The festival flower market cycle drives the economics: the photoperiod control allows growers to time their crop into the price spike windows.

Limitations

Night-lighting infrastructure consumes electricity continuously over the lighting window, with cost scaling by area. Voltage interruptions break the protocol and cause premature bud initiation. Uneven light distribution from poorly-placed bulbs produces non-uniform crops. The technique only delays flowering; it cannot advance flowering ahead of the natural critical day length.

See also Festival Flower Market Cycle, Mulching Drip Floriculture and Floriculture Seedling Nursery Tray System.

References

  1. Day light quality affects night-break response in chrysanthemum. ScienceDirect.
  2. How Blue Light Affects Flower Induction in Chrysanthemum. PubMed Central.