The daylight period for a region at 50 degrees north or south of the equator varies from a minimum of 73A hours in the winter to a maximum of 16V4 hours in the summer (June 21). The best guide to a particular plant's photoperiod is the latitude of its native habitat. Some plants such as Aldrovanda grow in a wide range of latitudes and can, therefore, survive under various photoperiods. Some plants such as the arctic and subarctic Pinguicula are very sensitive to photoperiod. If a wide range of plants from varying latitudes are grown together a compromise in photoperiod will be necessary. A photoperiod of a 14—17 hour day for those plants that do not require a dormant period has been successful.
Some hobbyists are experimenting with a 24-hour photoperiod. Some carnivorous plants have not flowered or if they have, do not set viable seed in cultivation. It could be that the photoperiod is critical to these plants.
The study of photoperiod is almost virgin territory which needs much more investigation.
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