Poinsettia Short Day Trigger Date

Locate the first caller-defined consecutive uninterrupted-dark run in measured/scheduled poinsettia nights; each date is night start and completion is following morning, not cultivar-specific flowering prediction.

Description

Short-day induction depends on uninterrupted dark periods over consecutive nights.

Short-day induction depends on uninterrupted dark periods over consecutive nights. A night-start date and completion on the following morning must be distinguished.^[1]

When to use Poinsettia Short Day Trigger Date

Use this tool to locate the first caller-defined consecutive uninterrupted-dark run in measured/scheduled poinsettia nights; each date is night start and completion is following morning, not cultivar-specific flowering prediction.

Prepare the plant, nutrient, light or scheduling measurements for the intended crop and period. Keep paired records aligned and confirm units and supplied target values.

How to use Poinsettia Short Day Trigger Date and understand its results

Prepare the plant, nutrient, light or scheduling measurements for the intended crop and period. Keep paired records aligned and confirm units and supplied target values.
Enter firstNightDate, uninterruptedDarkHoursByNight, callerMinimumDarkHours, callerConsecutiveInductiveNights using the field table and calculation rules, then run the tool.
Read firstQualifyingNightDate, modelInductionCompletionDate. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
firstNightDate	First night date	string	Required
uninterruptedDarkHoursByNight	Uninterrupted dark hours by night	list of number	Required
callerMinimumDarkHours	Caller minimum dark hours	number	Required
callerConsecutiveInductiveNights	Caller consecutive inductive nights	integer	Required

Use a valid UTC YYYY-MM-DD first-night date, nightly hours and threshold in [0,24], and a positive integer required-night count. Find the first completed run; return its first night and morning after its final night. If no run completes, report an input issue for right-censored induction.

qualifying run = required consecutive nights with dark hours ≥ caller minimum

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
firstQualifyingNightDate	First qualifying night date	string
modelInductionCompletionDate	Model induction completion date	string

json

{
  "input": {
    "firstNightDate": "2026-10-01",
    "uninterruptedDarkHoursByNight": [
      10,
      14,
      14,
      14,
      10
    ],
    "callerMinimumDarkHours": 12,
    "callerConsecutiveInductiveNights": 3
  },
  "output": {
    "firstQualifyingNightDate": "2026-10-02",
    "modelInductionCompletionDate": "2026-10-05"
  }
}

Limitations and assumptions

Thresholds and cultivar response are supplied assumptions. The result does not predict flowering dates.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Easter Lily Forcing Backward Count: Back-plan an Easter-lily forcing sequence from a supplied market date and stage durations/buffers, rounding each stage up to UTC days; no Easter computation or mutable cultivar forcing schedule. For a complementary task, use Supplemental Light Shortfall Hours: Invert measured natural-light deficit into supplementary hours with delivery loss and a caller available photoperiod; unmet photon budget is explicit, not a crop lighting recommendation.

References

Poinsettia Short Day Trigger Date — tool.io

Similar or alternative tools

Easter Lily Forcing Backward Count
Back-plan an Easter-lily forcing sequence from a supplied market date and stage durations/buffers, rounding each stage up to UTC days; no Easter computation or mutable cultivar forcing schedule.
Supplemental Light Shortfall Hours
Invert measured natural-light deficit into supplementary hours with delivery loss and a caller available photoperiod; unmet photon budget is explicit, not a crop lighting recommendation.